Startseite Optimization of biogas potential using kinetic models, response surface methodology, and instrumental evidence for biodegradation of tannery fleshings during anaerobic digestion
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Optimization of biogas potential using kinetic models, response surface methodology, and instrumental evidence for biodegradation of tannery fleshings during anaerobic digestion

  • Kavan Kumar V. EMAIL logo , R. Mahendiran , P. Subramanian , S. Karthikeyan , A. Surendrakumar , V. Kumargouda , Ravi Y. , Sharda Choudhary , Ravindra Singh und Arvind K. Verma
Veröffentlicht/Copyright: 19. September 2023
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Open Life Sciences
Aus der Zeitschrift Open Life Sciences Band 18 Heft 1

Abstract

The optimization of the batch size experiment was run for a hydraulic retention time of 45 days using proteolytic enzyme pretreatment. The highest amounts of biogas were produced in comparison to conventional BDS (25:75), which is not processed with enzymes, and there was an increase in the biogas generation of 13.9 and 18.57%. The kinetic models show the goodness of fit between 0.993 and 0.998 and the correlation coefficient’s value domain was [−1, 1] from a statistical perspective. The Box–Behnken design was carried out using the response surface methodology at different levels of independent parameters to optimize the process. Different instruments were evaluated to determine the chemical structure change and the contamination of the different treatments and the raw sample of tannery fleshings was determined. Thermogravimetric analysis was conducted to determine the loss of weight on thermal degradation. The Fourier transform infrared spectrometry was carried out to determine the different functional groups, such as –OH, –CH, –NH, and C–O, present in the samples of tannery fleshings. Scanning electron microscopy and energy dispersive X-ray analysis were carried out to determine the morphological alterations in the substrate, digestate, enzyme-pretreated fleshings, and the chemical composition of samples.

Graphical abstract

Keywords: tannery fleshings; proteolytic enzymes; biogas; kinetics and instrumental analysis

1 Introduction

Tannery industries are among the most polluting sectors due to the generation of high solid wastes and wastewater [1]. The production of tannery primary sludge and secondary sludge is enormous, and when tannery enterprises are structured as concentrated districts, tannery wastewater is treated in specialized industrial wastewater treatment plants [2]. Pre-tanning, tanning and crusting, and refinishing procedures are all steps in the multi-step sequential process of tanning leather. Therefore, depending on the production phase they are produced from, tannery solid wastes might vary greatly in terms of quantity and quality. Pre-tanning and tanning activities produce the majority of the pollution burden. The majority of pre-tanning solid wastes consist of fleshing, skin trims, and hair. Due to their high chemical pollution content and the presence of resistant chemicals, tannery fleshings (TF) and tannery primary sludge have historically been managed through landfill disposal and cremation [3]. Anaerobic digestion (AD) has emerged as a viable option for the integrated and sustainable management of tannery wastewater and solid wastes in response to new strict legislation and environmental policies that encourage alternative eco-friendly treatments. Other alternate treatments, such as AD, have been suggested to divert fleshing and other leather wastes from the final landfill disposal or incineration in favour of resource and/or energy recovery [4,5]. Composting, recovering tanning ingredients, producing biodiesel, and producing proteolytic enzymes from fleshing fermentation are a few of the described bioconversion processes. Additionally, TF has been subjected to physicochemical treatments for more than 20 years for the recovery of fat and protein as well as the production of glue, typically in centralized industrial settings where the economies of scale make it affordable to collect and treat TF for material recovery [6]. For instance, a single company (SGS, Pisa, Italy) collects fleshing from roughly 400 tanneries in the Tuscany tannery district, separates the fat and protein fractions, and then markets them to the cosmetic and fertilizer industries, respectively [7]. However, such a treatment necessitates laborious and energy-intensive procedures, and the market for the resulting by-products is subject to significant price swings [8].

Numerous research studies are currently available mentioning tannery districts in India, China, Latin America, and Italy. In general, studies on the AD of leather solid wastes concur that the process is feasible while cautioning against potential operational issues linked to imbalanced C/N ratios and inhibiting conditions from ammonia, long-chain fatty acids, and sulphur dioxide [9,10]. Furthermore, tanning processes try to stabilize the collagen in leather, biological treatments, and in particular AD, proved to perform better for untanned wastes than for tanned ones. The analysis of the anaerobic biodegradability of tannery wastes containing various concentrations of chrome, the lower the methane output, primarily because of the low hydrolysis of tanned stable material, the higher the chrome content. The same authors noted that to avoid low-performance issues, careful selection of seed sludge and substrate hydrolysis pre-treatments is needed. The biodegradability of untanned, chrome-tanned, and vegetable-tanned leather solid wastes was also studied by Damtie et al. [11]. Untanned wastes produced the maximum amount of methane; however, vegetable-tanned wastes were more biodegradable than chrome-tanned ones. The same study also assessed the impact of detanning pretreatment, which led to an improvement in the biodegradability of wastes.

However, the bulk of the research that has been reported on AD has used a combination of tannery wastes and other substrates that came from the tannery industry. The goal of this research is to better understand how AD is used in technology. In the context of its use as an on-site treatment option for decentralized tanneries, of single Tannery Fleshing. Particularly, critical conditions related to the liquefaction of tannery fleshings have been studied in order to define the applicability range of proteolytic enzymes to reduce the size of fleshings for the process of AD. The investigation of sample analysis techniques and equipment to study the changes in the structure, chemical composition, thermal decomposition, and functional groups in the organic substance were estimated using the thermogravimetric analysis (TGA), Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), and energy dispersive X-ray (EDAX) analysis.

2 Materials and methods

2.1 Physicochemical properties and instrumental analysis of feedstock and inoculum

The physicochemical properties, such as total solids, volatile solids, total organic carbon, total Kjeldahl nitrogen, and C/N ratio, were estimated using the standard procedures mentioned in the American Public Health Association [12].

2.2 Enzymatic pretreatment of tannery fleshings

The application of enzymes in waste treatment using a biotechnological method is a new area of research. The use of enzymes to speed up the digestive process is an option, and the current study uses proteolytic enzymes. Proteolytic enzymes are enzymes that help in the breakdown of proteins [13]. These enzymes are extracted from animals, bacteria, plants, and fungi. Some of the proteolytic enzymes may be found in supplements like ficin, papain, trypsin, chymotrypsin, and trypsin. In this study, trypsin and papain enzymes were selected at 5U for the treatment of 1 kg fleshings.

2.2.1 Trypsin enzyme pretreatment

Trypsin is one of the three major types of industrial enzymes, with applications in the leather industry, food processing, and bioremediation. A protease enzyme catalyses the breakdown of proteins into smaller polypeptides or single amino acids. Hydrolysis, a reaction in which water breaks the bonds, is used to disrupt the peptide links within the proteins.

2.2.2 Papain enzyme pretreatment

Papain enzyme is obtained from the papaya fruit. The papain enzyme is also called papaya proteinase I and has a broad pH of 5–7.5 and a temperature stability of 70–90°C. It is very popular in various applications. It is used as a meat tenderizer; the enzyme makes its way into muscle and hydrolyses primarily connective protein tissues (collagen) and softens the muscle. Papain has to be used in a low quantity to prevent the high liquefaction of the substrates.

2.2.3 Batch-scale experiment for pretreated tannery fleshings

The study on biomethane potential using batch-scale reactors was carried out with the best treatment selected from the batch experiment. Another study was carried out after the treatment of tannery fleshings with 82.5 IU of proteolytic enzymes with a feeding bio-digested slurry and tannery fleshings in the proportion of 0.25:0.75 with three treatments. The first treatment was performed without enzyme addition, and the other two treatments were performed using trypsin and papain enzymes. After feeding substrate and inoculum into the reactors, the reactors were closed and provided with a gas outlet. Duplicate reactors were operated to find the repeatability, and the performance was reported. The daily biogas production was measured using the water displacement method, as shown in Figure 1, and the methane content was estimated using a 5% alkali solution.

Figure 1 Water displacement set-up for biogas measurement.
Figure 1

Water displacement set-up for biogas measurement.

2.3 Kinetic studies for biogas production

Kinetic analysis is a commonly used concept for identifying the significance of inter-variable interactions in order to guide experimental design, evaluate experimental results, and describe particular system performance. Experimental kinetic studies can be used to simulate digester behaviour and forecast the biogas output of a running plant under similar conditions. To forecast biogas output and evaluate kinetic parameters, a first-order model and modified Gompertz models were used in this work. Using IBM SPSS software 25.0, the experimental cumulative biogas was utilized to estimate the parameters using non-linear regression.

2.3.1 First-order kinetic model

The following first-order kinetics equation is used to predict the biogas yield production:

(1) P = P 0 [ 1 − exp ( − k × t ) ] ,

where P is the cumulative biogas yield, P 0 is the ultimate biogas yield, k is the first-order rate constant, and t is the time. The first-order kinetics used an empirical linear regression to determine the rate of reaction, where the value of the slope of the linear plot represents the given substrate characteristics. However, the first-order model’s linear form, which is an exponential form, cannot be used to appropriately account for and predict cumulative biogas production during the entire process, particularly after the exponential phase.

2.3.2 Modified Gompertz model

The modified Gompertz model is a non-linear kinetic model, which is used to calculate the length of the lag phase and biogas production rate:

(2) p = P 0 × exp − exp R × 2.7183 P 0 ( L − t ) + 1 ,

where L is the lag phase duration, R is the biogas production rate, and P 0 is the biogas potential at time t. The standard statistical metric is used to study the model performance. The root mean square error (RMSE) is calculated for the actual and predicted biogas production values using the following equation:

(3) RMSE = 1 m ∑ j = 1 m ⅆ j y j 2 1 2 ,

where m is the number of data pairs, d is the difference between experimental and predicted yield, and Y is the measured biogas yield.

2.3.3 Correlation studies for model parameters

The correlation coefficients for different parameters of first-order and modified Gompertz kinetic models were studied using ORIGIN 2019 software. The results are elaborated with the proper justification in the following headings of the research work.

2.3.4 Optimization of parameters for biogas production

Response surface methodology (RSM) is a significant statistical approach for the investigation of complicated processes. As a result, these techniques were used to optimize the process parameters for the production of biogas from the proteolytic pretreated tannery fleshings. RSM is a combination of statistical approaches for conducting experiments, developing models, assessing the impacts of variables, and locating optimal conditions for desired responses [14]. The RSM analysis involves fitting the experimental values of biogas production to a standard equation and then optimizing the value using appropriate optimization tools or mathematical solutions. The process parameters such as pH, temperature, and hydraulic retention time (HRT) were optimized for maximum biogas production.

2.3.5 Design of experiments

The RSM deals with finding the most optimal/desired parameters for an experiment. To design the experiment, the Box–Behnken design (BBD) was used, and the design consisted of three variables and three levels including the 17 experiments formed by 5 central points [15]. Three independent variables considered to influence biogas production are pH, temperature, and HRT, as shown in Table 1. This shows the RSM experimental design of independent parameters and layout for these three levels and three variables. During the experiment, all of these variables and responses were properly measured and evaluated experimentally. The RSM for BBD in the experimental data was analysed using the package of design expert version 12.0 software.

Table 1

Levels of input values for BMP studies of tannery fleshings

Variables Coded Range and levels
Low level (−1) Centre level (0) High level (1)
pH X1 7 7.5 8
Temperature (°C) X2 28 32 36
HRT (days) X3 1 23 45

2.4 Characterization of substrate and digestate

Tannery fleshings were characterized before the experimental trials and the obtained digestate was also characterized using different analytical instruments to check the parametrical change in the output. The procedures adopted are briefly mentioned. The samples were also characterized using TGA, FT-IR analysis, SEM analysis, and EDAX analysis [16]. The samples were pretreated using the proteolytic (trypsin and papain) enzymes to reduce the time of hydrolysis in the AD process.

2.4.1 TGA

TGA is a technique used to estimate the thermal stability of organic materials and volatile component fractions by considering that the weight change occurs in a sample with a constant rate of heating. About 8.6920 g of raw lime and 7.3230 g of delimed tannery fleshing samples were analysed to determine the changes occurring in the thermal process. The Ramp method used in TGA Q50 V20.13 Build 39 with N2 as an inert gas with a flow rate of 100 mL/min [17].

2.4.2 FT-IR analysis

Substrate, digestate, and proteolytic enzyme-treated samples were air-dried to remove moisture. The dried sample pellets were made in a 5:1 ratio and subjected to FT-IR analysis using a transmission mode [18]. The measurements were carried out in the mid-infrared range wavenumber between 4,000 and 500 cm−1. The measurement information of FTIR settings is given in Table 1.

2.4.3 SEM and EDAX analysis

The air-dried samples were coated with gold in an argon medium. SEM and EDAX analyses were carried out on a scanning device attached to a QUANTA 250 Everhart Thornley Detector electron microscope at 8 kV, accelerated with an electron beam [19]. The digestion of the substrate during the AD is determined by SEM analysis, and the compounds in the sample are determined by the EDAX analysis.

3 Results and discussion

The results obtained from the experiments carried out are discussed in this section. The physicochemical properties of tannery fleshings and inoculum, daily biogas production, methane percentage, and bio-digestate values are presented.

3.1 Physicochemical properties of the feedstock and inoculum

The estimated physical and chemical parameters for tannery fleshings and the inoculum as bio-digested slurry are given in Table 2.

Table 2

Physicochemical properties of fleshings, cow dung, elephant dung, and bio-digested slurry

Sl. No. Parameter Tannery fleshings Bio-digested slurry
1 pH 11.0–12.0* 7.0–8.0*
2 Moisture content (%) 82.1 ± 0.20* 79.24 ± 0.78*
3 Total solids (%) 17.9 ± 0.20* 20.76 ± 0.78*
4 Volatile solids (%) 66 41 ± 1.44* 69.93 ± 0.86*
5 Total organic carbon (g/kg) 0.95 ± 0.01* 19.7 ± 0.34*
6 Total Kjeldahl nitrogen (g/kg) 36.0 ± 2.1* 1.09 ± 0.71*
7 C/N ratio 9.3 ± 0.55* 18.07 ± 0.48*

*Values are expressed as mean ± SD on a dry basis.

3.2 Batch AD of pretreated tannery fleshings

The pretreatment helps to exploit the substrate for better biogas production. The best treatment was selected from a previous study, and an additional biomethane potential experiment was carried out for the tannery fleshings pretreated with trypsin and papain enzyme. The disintegrated tannery fleshings were collected and subjected to the batch scale AD experiment for a retention period of 45 days. The daily gas measurement was observed using the water displacement method and methane content was estimated. The gas production and methane content are presented in Figures 2 and 3.

Figure 2 Daily biogas generation of the enzymatic pretreated tannery fleshings.
Figure 2

Daily biogas generation of the enzymatic pretreated tannery fleshings.

Figure 3 Comparative methane content of the pretreated tannery fleshing treatments.
Figure 3

Comparative methane content of the pretreated tannery fleshing treatments.

Maximum biogas of 12,118 mL from the standard BDS (25:75), 14073.25 mL from the trypsin-treated BDS (25:75), and 14881.25 mL from papain-treated BDS (25:75) were generated with methane contents of 63.77, 65.64, and 66.29%. There is an increase in the biogas production of 13.9% for trypsin and 18.57% for papain treatment compared to standard BDS (25:75) without pretreatment.

3.3 Simulation of experimental data using first-order kinetics and modified Gompertz model and correlation coefficient

In this section, we predicted the biogas production rate using the kinetic models. The simulated experimental and predicted values are shown in Figures 4 and 5, whereas the goodness of fit for the first-order kinetic model ranges from 0.994 to 0.998 and the goodness of fit for the modified Gompertz model ranges from 0.983 to 0.993. The different parameters obtained from the kinetic model studies are presented in Table 3.

Figure 4 Simulation values for experimental and predicted values of biogas production from the first-order kinetic model.
Figure 4

Simulation values for experimental and predicted values of biogas production from the first-order kinetic model.

Figure 5 Simulation values for experimental and predicted values of biogas production from the modified Gompertz model.
Figure 5

Simulation values for experimental and predicted values of biogas production from the modified Gompertz model.

Table 3

Simulation values for experimental and predicted values of biogas production from the first-order kinetic model

Sl. no. Parameter Standard Trypsin Papain
First-order kinetic model
1. C – Experimental (mL) 12,118 14073.25 14881.25
2. C – Predicted (mL) 12399.56 14745.20 14735.53
3. P 0 (mL/day) 402.27 412.73 439.82
4. t (days) 0.043 0.018 0.044
5. Residual sum of squares 1087103.81 2208444.25 4233332.71
6. Corrected sum of squares 525677884.2 825190107.8 716,421604
7. R 2 0.998 0.917 0.994
8. RMSE 2.80 3.97 1.74
Modified Gompertz model
1. C – Experimental (mL) 12,118 14073.25 14881.25
2. C – Predicted (mL) 12102.60 14945.8 14558.25
3. R (mL/day) 407.70 433.04 446.44
4. t (days) 1.615 2.057 3.071
5. Residual sum of squares 3579366.18 5892716.24 12301598.6
6. Corrected sum of squares 525677884.2 825190107.8 716,421604
7. R 2 0.993 0.992 0.983
8. RMSE 1.04 1.94 3.42

As shown in Table 3, the daily biogas production potential ranges from 402.27 to 439.82 mL/g VS for the first-order kinetic model and 407.70 to 446.44 mL/g VS for the modified Gompertz model.

3.4 Correlation studies for kinetic model parameters

The relation between the different parameters of kinetic model parameters using first-order and modified Gompertz models are shown in Tables 4 and 5.

Table 4

Correlation coefficients of first-order kinetic model parameters

Correlation coefficient G K
Standard samples
G 1.000 −0.966
K −0.966 1.000
Trypsin enzyme sample
G 1.000 −0.996
K −0.996 1.000
Papain enzyme sample
G 1.000 −0.963
K −0.963 1.000
Table 5

Correlation coefficient of the modified Gompertz kinetic model parameters

Correlation coefficient P R L
Standard samples
P 1.000 −0.714 0.903
R −0.714 1.000 −0.537
L 0.903 −0.537 1.000
Trypsin enzyme sample
P 1.000 −0.843 0.814
R −0.843 1.000 −0.732
L 0.814 −0.732 1.000
Papain enzyme sample
P 1.000 −0.749 −0.582
R −0.749 1.000 0.915
L −0.582 0.915 1.000

The correlation coefficient’s value domain is [−1, 1] from a statistical perspective. Many other investigations have confirmed it, in addition to our own. In addition to highlighting the linear relationship between two data sets in a space of observation objects, the correlation coefficient also highlights the variability of two data sets, making this value domain more important than [0, 1]. Two datasets might exhibit the same pattern or a downward trend (in the case of positive correlation). Additionally, the first data set might be increased while the second is decreased; conversely, in the event of a negative correlation, the first data set could be decreased while the second is increased.

3.5 Optimization of the BMP experiment for tannery fleshings

One of the most crucial factors to be considered in an anaerobic digester is the precise anticipation of the volume of producible biogas. The potential biogas yield is a function of the input factors and depends on the chemical makeup of the feedstock. The influence of the input variables on the biogas yield is expressed here in the simplified form of the coded and actual values of the independent variables [20]. The positive and negative signals placed in front of each model phrase show both a complementary and a competitive impact on the reaction.

3.5.1 Analysis of variance (ANOVA)

The model F-values imply that the model is significant. There is only a 0.01% chance that this large F-value could occur due to noise. p-values <0.0500 indicate that the model terms are significant; this was also reported by some researchers [21]. In this case, C is a significant model term. Values greater than 0.1000 indicate that the model terms are not significant. If there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve the model. The ANOVA values of the models are shown in Tables 6–8.

Table 6

ANOVA for the standard sample of tannery fleshings

Source Sum of squares df Mean square F-value p-value
Model 1.919 × 105 3 63963.38 121.94 <0.0001 Significant
A – pH 0.0000 1 0.0000 0.0000 1.0000
B – Temperature 0.0000 1 0.0000 0.0000 1.0000
C – HRT 1.919 × 105 1 1.919 × 105 365.83 <0.0001
Residual 6818.89 13 524.53
Lack of fit 6818.89 9 757.65
Pure error 0.0000 4 0.0000
Cor total 1.987 × 105 16
Table 7

ANOVA for trypsin-pretreated tannery fleshings

Source Sum of squares df Mean square F-value p-value
Model 2.211 × 105 3 73704.17 228.00 <0.0001 Significant
A – pH 0.0000 1 0.0000 0.0000 1.0000
B – Temperature 0.0000 1 0.0000 0.0000 1.0000
C – HRT 2.211 × 105 1 2.211 × 105 683.99 <0.0001
Residual 4202.47 13 323.27
Lack of fit 4202.47 9 466.94
Pure error 0.0000 4 0.0000
Cor total 2.253 × 105 16
Table 8

ANOVA for papain-pretreated tannery fleshings

Source Sum of squares df Mean square F-value p-value
Model 3.482 × 105 3 1.161 × 105 14990.36 <0.0001 Significant
A – pH 0.0000 1 0.0000 0.0000 1.0000
B – Temperature 0.0000 1 0.0000 0.0000 1.0000
C – HRT 3.482 × 105 1 3.482 × 105 44971.07 <0.0001
Residual 100.65 13 7.74
Lack of fit 100.65 9 11.18
Pure error 0.0000 4 0.0000
Cor total 3.483 × 105 16

The experimental data were fitted using a cubic model, and the statistical significance for linear terms for biogas generation was calculated as indicated in the tables. By using the least-squares method, the R 2 value ranged from 0.9368 to 0.996, indicating a satisfactory fit between the model and the data. The model’s F values indicate that it is significant (P 0.0001), according to the data. Significant linear terms are present (P 0.0001). The developed model was sufficient for forecasting the response because the lack of fit F value was non-significant [22]. This demonstrated that the model did not contain the non-significant terms. Consequently, one may utilize this model to explore the design space [23]. The probability and the actual vs predicted values of the optimization are shown in Figures 6–11. The biogas production equations for different treatments are as follows:

Figure 6 Actual and predicted values of biogas production from the standard sample of tannery fleshings.
Figure 6

Actual and predicted values of biogas production from the standard sample of tannery fleshings.

Figure 7 Normal probability plot for the standard sample of tannery fleshings.
Figure 7

Normal probability plot for the standard sample of tannery fleshings.

Figure 8 Actual and predicted values of biogas production from trypsin-pretreated tannery fleshings.
Figure 8

Actual and predicted values of biogas production from trypsin-pretreated tannery fleshings.

Figure 9 Normal probability plot for trypsin-pretreated tannery fleshings.
Figure 9

Normal probability plot for trypsin-pretreated tannery fleshings.

Figure 10 Actual and predicted values of biogas production from papain-pretreated tannery fleshings.
Figure 10

Actual and predicted values of biogas production from papain-pretreated tannery fleshings.

Figure 11 Normal probability plot for papain-pretreated tannery fleshings.
Figure 11

Normal probability plot for papain-pretreated tannery fleshings.

Biogas production = 368.28 + 7.364A + 9.447B – 7.04C (standard sample).

Biogas production = 381.98 – 3.605A – 4.97B – 7.55C (trypsin-pretreated sample).

Biogas production = 459.56 + 6.238A + 8.148B – 9.482C (papain-pretreated sample).

3.6 Digestate characteristics analysis of pretreated fleshings

At the end of digestion, once the gas production ceases, the digestate was collected from the batch scale experiment and analysed for the total solid reduction, volatile solid reduction, volatile fatty acids, and alkalinity of the tannery fleshings. The results are given in Table 9.

Table 9

Performance data of the biomethane potential for the pretreated substrate of 45 days HRT

Parameter Standard Trypsin Papain
VS in the feedstock (g) 11.37 11.37 11.37
I/S ratio 0.33 0.33 0.33
Total biogas generated (mL) 12,118 14073.25 14881.25
Biogas generated per gram of VS added (mg/L) 1065.78 1237.75 1308.82
Methane volume (mL) 7727.64 9279.9 9864.78
Methane content (%) 63.77 65.64 66.29
Methane yield per gram of VS added (mL/g) 679.65 816.17 867.61
Specific CH4 production rate (mL CH4/g VS/day) 28.31 34.00 36.15
TS reduction (%) 47.53 51.28 52.41
VS reduction (%) 38.84 38.91 39.93
Volatile fatty acids (mg/L) 800 740 690
Alkalinity (mg/L) 4,500 3,700 2,900
VFA/alkalinity ratio 0.17 0.2 0.23

The biogas and methane content of 14881.25 mL was observed from the papain-treated BDS (25:75) with a gas production at 1308.82 mL/g of VS added. The total gas production of 14073.25 mL was found from trypsin-treated BDS (25:75) at 1237.75 mL/g VS and a methane content of 9279.9 at 816.17 mL/g of VS for trypsin and 9864.78 mL and 867.61 mL/g of VS added for papain treatment. A total solid reduction of 51.28 and 52.41% and volatile solid reduction of 38.91 and 39.93% were reported. It was observed that the alkalinity was in the range of 2,900–4,500 mg/L considering all the reactors. The volatile fatty acids were in the range of 690–800 mg/L and well within 500–3,000 mg/L, as mentioned by Sri Bala Kameshwari et al. [24].

3.7 Instrumental evidence of the tannery fleshings

The analysis of the samples was carried out by TGA for thermal degradation of the sample, SEM for the identification of structure, and FT-IR spectrometry for the identification of functional groups.

3.7.1 TGA

The selected two samples, tannery raw fleshing and treated fleshing samples, show different patterns of weight loss with thermal treatment, as shown in Figures 12 and 13. The loss of moisture content was observed to increase from the ambient to 1,000°C. The TG and DTG curves of the analysis show the respective stages of biomass degradation during the TGA. The TGA of tannery fleshings shows three different phases, namely: moisture removal, devolatization, and biochar formation [25].

Figure 12 TGA of the raw tannery fleshing sample.
Figure 12

TGA of the raw tannery fleshing sample.

Figure 13 TGA of the treated tannery fleshing sample.
Figure 13

TGA of the treated tannery fleshing sample.

The initial moisture removal is observed from ambient temperature to 140°C; cellulose and hemicellulose degradation occurs from 160 to 380°C and the biochar formation occurs from 450 to 600°C. At temperatures of 600–800°C, a peak is observed due to the presence of some volatile compounds in the raw limed tannery fleshings [26]. As shown in Figure 12, the thermal degradation of the raw tannery fleshing occurs in five steps with weight decrease percentages of 43.21, 21.48, 12.58, 2.943, and 4.571%. As shown in Figure 13, the thermal degradation of the treated tannery fleshing occurs in three steps with weight decrease percentages of 79.35, 5.449, and 10.31%, where the thermal degradation percentage of the treated sample is more than that of the raw sample. Similar results were obtained in the work conducted by Fathima et al. [27].

3.7.2 FT-IR analysis

FT-IR analysis was performed for the substrate, digestate, and enzyme pretreatment samples. The functional groups of substances contained in the samples were identified using the FT-IR spectra. The spectra of the samples are shown in Figure 14(a) and (b).

Figure 14 Comparison of FT-IR spectra for the (a) substrate and digestate, and (b) substrate, trypsin, and papain treatment.
Figure 14

Comparison of FT-IR spectra for the (a) substrate and digestate, and (b) substrate, trypsin, and papain treatment.

Due to the overlap of –OH, –CH, and –NH stretching in FT-IR spectra, a large envelope from 4,000 to 400 cm−1 is observed. The FTIR spectrum of leather fleshing (delimed, digestate, proteolytic treated) sample showed –OH stretching of protein molecules in the wavelength between 3,700 and3,600 cm−1 but it was not identified in other treated samples of fleshings [28]. The asymmetric and symmetric peaks between 1,300 and 1,080 cm−1 were assigned to C–O by the presence of carboxylic acids, esters, and ethers. In-plane bending peaks detected from 1,680 to 1,620 cm−1, attributed to C–H due to the presence of hydrocarbons, confirm the occurrence of –CH stretching (hexane, propane). In-plane bending peaks detected at 1,660–1,350 cm−1, attributed to N–H due to the presence of amines, confirm the presence of –NH stretching [29]. The presence of alkynes is shown by the peaks at 2,140–2,100 cm−1. The strong N–O bond at 900–700 cm−1 and plane bending of ammonia at 1,290–1,090 cm−1 indicated the presence of nitro compounds. Similar results of FTIR were reported by Devaraj et al. [30] for co-digestion of tannery solid wastes by the optimization of mix proportions.

The treatment of fleshings with proteolytic enzymes shows the notable changes in the structure. Minor alterations were observed in the amine groups. The conversion of amide bands to amine groups followed by the formation of new acid groups was observed in the FTIR analysis as well as the biodegradation of ketone and –C═O groups to new group of acids was observed [31]. The degradations of the functional groups are helpful in the production of amino acid groups to cut down the hydrolysis process during the AD of tannery fleshings to produce the biogas [32].

3.7.3 SEM analysis

The morphological alterations in the substrate, digestate, and enzyme-pretreated fleshings were investigated by SEM. The SEM images are shown in Figure 15(a)–(d). The SEM image reveals the presence of tiny fibrous tissue dispersion in the substrate. Fibrous tissues are connected to the protein matrix. The fibrous protein was digested, as seen by the SEM image of the digestate and the disintegration occurred in the pretreated samples. The digestate has a rough and uneven surface with voids, which could be attributable to the emission of biogas during the digestion process [33].

Figure 15 SEM images of the (a) substrate, (b) digestate, (c) trypsin, and (d) papain enzymatic treatment.
Figure 15

SEM images of the (a) substrate, (b) digestate, (c) trypsin, and (d) papain enzymatic treatment.

In addition, the SEM images of the digestate reveal the presence of various-sized particles, which is consistent with the particle size analyses. The visual changes in the tannery fleshing SEM samples confirm the activity of protein hydrolysis during the pretreatment using proteolytic enzymes. There is a notable shrinkage and disintegration of the structure observed at an initial level. The biodegradation of the protein during the pretreatment resulted in the change in the structure of tissues which are even visualized through the SEM images. Similar works on SEM were carried out by other researchers for protein hydrolysis [34].

From the EDAX analysis, it is evident that there is not much variation in the chemical composition of organic and inorganic compounds like carbon (46.42–59.69%) and oxygen (22.26–26.42%). The nitrogen content of the proteolytic enzyme-treated samples showing the highest chemical composition (3.62–19.36%) compared to those of the raw and digestate samples. This increase in the nitrogen content is helpful in the alternation of the C/N ratio of the substrate for the process of AD to produce the biogas. The other compounds like sodium, aluminium, magnesium, sulphur, chlorine, potash, and calcium show the least in all the samples. No contamination peaks were observed in the samples, which represent the chemical purity of the samples. The presence of the compounds in the substrate is shown in Figures 16–19.

Figure 16 EDAX analysis of the raw fleshing sample.
Figure 16

EDAX analysis of the raw fleshing sample.

Figure 17 EDAX analysis of the digestate sample.
Figure 17

EDAX analysis of the digestate sample.

Figure 18 EDAX analysis of the trypsin-treated sample.
Figure 18

EDAX analysis of the trypsin-treated sample.

Figure 19 EDAX analysis of the papain-treated sample.
Figure 19

EDAX analysis of the papain-treated sample.

4 Conclusion

The pretreatment studies for tannery fleshings were carried out using proteolytic enzymes such as trypsin and papain for the liquefaction of fleshings with a 5U for the treatment of 1 kg fleshings. The batch scale experiment was carried out for a retention period of 45 days and the daily biogas was measured using the water displacement method. The maximum biogas of 12,118 mL from the standard BDS (25:75), 14073.25 mL from the trypsin-treated BDS (25:75), and 14881.25 mL from papain-treated BDS (25:75) were generated with methane contents of 63.77, 65.64, and 66.29%, respectively. There is an increase in the biogas production from 13.9 and 18.57% compared to standard BDS (25:75), which is not pretreated with enzyme. The kinetic models show the goodness of fit between 0.993 and 0.998. The correlation coefficient domain is [−1, 1] from a statistical perspective, which was observed in this work. The instrumental study of tannery fleshings concludes that TGA shows the weight loss of the sample with the thermal application for the analysis of thermal degradation of tannery fleshings from ambient temperature to 1,000°C. The different stages of sample degradation were observed from the TG and DTG profiles, which can be helpful for further thermochemical applications. The FTIR analysis shows the different functional groups stretching present in the samples at wavelengths between 400 and 4,000 cm−1, which confirms the presence of different functional groups in the tannery fleshings like –OH, –CO, –NH, –CH, N–O, NH3 with different peaks. Biodegradation of ketone and –C═O groups into new groups of acids was noticed. The synthesis of amino acid groups from these functional group degradations can speed up the hydrolysis process during the AD of tannery fleshings to create biogas. The SEM image revealed the presence of tiny fibrous tissue dispersion in the matrix. The fibrous protein was digested, as seen by the SEM image of the digestate and the disintegration occurred in the pretreated samples. Prior to digestion, a fine spread of fibrous tissues bound to proteins could be seen in SEM images; however, the fibrous structures were not present in the digestate. The identification of secondary metabolites produced during the digestive process is aided by instrumental analysis. The digestate has a rough and uneven surface with voids, which could be attributable to the emission of biogas during the digestion process. The EDAX analysis for the different samples shows variation in the chemical composition and also shows the increase of nitrogen in enzyme-treated samples, with carbon (46.42–59.69%) and oxygen (22.26–26.42%). The nitrogen content of the proteolytic enzyme treated showed the highest chemical composition (3.62–19.36%). The digestate of the AD process can be used as soil amendment for better crop yields.

Acknowledgments

This work was supported by Renewable Energy Engineering, Agricultural Engineering College and Research Institute, Tamil Nadu Agricultural University, Coimbatore, India.

  1. Funding information: Authors state no funding involved.

  2. Conflict of interest: Authors state no conflict of interest.

  3. Data availability statement: The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

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Received: 2023-02-23
Revised: 2023-06-01
Accepted: 2023-08-16
Published Online: 2023-09-19

© 2023 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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  158. A case report of diagnosis and dynamic monitoring of Listeria monocytogenes meningitis with NGS
  159. Effect of autologous platelet-rich plasma on new bone formation and viability of a Marburg bone graft
  160. Small breast epithelial mucin as a useful prognostic marker for breast cancer patients
  161. Continuous non-adherent culture promotes transdifferentiation of human adipose-derived stem cells into retinal lineage
  162. Nrf3 alleviates oxidative stress and promotes the survival of colon cancer cells by activating AKT/BCL-2 signal pathway
  163. Favorable response to surufatinib in a patient with necrolytic migratory erythema: A case report
  164. Case report of atypical undernutrition of hypoproteinemia type
  165. Down-regulation of COL1A1 inhibits tumor-associated fibroblast activation and mediates matrix remodeling in the tumor microenvironment of breast cancer
  166. Sarcoma protein kinase inhibition alleviates liver fibrosis by promoting hepatic stellate cells ferroptosis
  167. Research progress of serum eosinophil in chronic obstructive pulmonary disease and asthma
  168. Clinicopathological characteristics of co-existing or mixed colorectal cancer and neuroendocrine tumor: Report of five cases
  169. Role of menopausal hormone therapy in the prevention of postmenopausal osteoporosis
  170. Precisional detection of lymph node metastasis using tFCM in colorectal cancer
  171. Advances in diagnosis and treatment of perimenopausal syndrome
  172. A study of forensic genetics: ITO index distribution and kinship judgment between two individuals
  173. Acute lupus pneumonitis resembling miliary tuberculosis: A case-based review
  174. Plasma levels of CD36 and glutathione as biomarkers for ruptured intracranial aneurysm
  175. Fractalkine modulates pulmonary angiogenesis and tube formation by modulating CX3CR1 and growth factors in PVECs
  176. Novel risk prediction models for deep vein thrombosis after thoracotomy and thoracoscopic lung cancer resections, involving coagulation and immune function
  177. Exploring the diagnostic markers of essential tremor: A study based on machine learning algorithms
  178. Evaluation of effects of small-incision approach treatment on proximal tibia fracture by deep learning algorithm-based magnetic resonance imaging
  179. An online diagnosis method for cancer lesions based on intelligent imaging analysis
  180. Medical imaging in rheumatoid arthritis: A review on deep learning approach
  181. Predictive analytics in smart healthcare for child mortality prediction using a machine learning approach
  182. Utility of neutrophil–lymphocyte ratio and platelet–lymphocyte ratio in predicting acute-on-chronic liver failure survival
  183. A biomedical decision support system for meta-analysis of bilateral upper-limb training in stroke patients with hemiplegia
  184. TNF-α and IL-8 levels are positively correlated with hypobaric hypoxic pulmonary hypertension and pulmonary vascular remodeling in rats
  185. Stochastic gradient descent optimisation for convolutional neural network for medical image segmentation
  186. Comparison of the prognostic value of four different critical illness scores in patients with sepsis-induced coagulopathy
  187. Application and teaching of computer molecular simulation embedded technology and artificial intelligence in drug research and development
  188. Hepatobiliary surgery based on intelligent image segmentation technology
  189. Value of brain injury-related indicators based on neural network in the diagnosis of neonatal hypoxic-ischemic encephalopathy
  190. Analysis of early diagnosis methods for asymmetric dementia in brain MR images based on genetic medical technology
  191. Early diagnosis for the onset of peri-implantitis based on artificial neural network
  192. Clinical significance of the detection of serum IgG4 and IgG4/IgG ratio in patients with thyroid-associated ophthalmopathy
  193. Forecast of pain degree of lumbar disc herniation based on back propagation neural network
  194. SPA-UNet: A liver tumor segmentation network based on fused multi-scale features
  195. Systematic evaluation of clinical efficacy of CYP1B1 gene polymorphism in EGFR mutant non-small cell lung cancer observed by medical image
  196. Rehabilitation effect of intelligent rehabilitation training system on hemiplegic limb spasms after stroke
  197. A novel approach for minimising anti-aliasing effects in EEG data acquisition
  198. ErbB4 promotes M2 activation of macrophages in idiopathic pulmonary fibrosis
  199. Clinical role of CYP1B1 gene polymorphism in prediction of postoperative chemotherapy efficacy in NSCLC based on individualized health model
  200. Lung nodule segmentation via semi-residual multi-resolution neural networks
  201. Evaluation of brain nerve function in ICU patients with Delirium by deep learning algorithm-based resting state MRI
  202. A data mining technique for detecting malignant mesothelioma cancer using multiple regression analysis
  203. Markov model combined with MR diffusion tensor imaging for predicting the onset of Alzheimer’s disease
  204. Effectiveness of the treatment of depression associated with cancer and neuroimaging changes in depression-related brain regions in patients treated with the mediator-deuterium acupuncture method
  205. Molecular mechanism of colorectal cancer and screening of molecular markers based on bioinformatics analysis
  206. Monitoring and evaluation of anesthesia depth status data based on neuroscience
  207. Exploring the conformational dynamics and thermodynamics of EGFR S768I and G719X + S768I mutations in non-small cell lung cancer: An in silico approaches
  208. Optimised feature selection-driven convolutional neural network using gray level co-occurrence matrix for detection of cervical cancer
  209. Incidence of different pressure patterns of spinal cerebellar ataxia and analysis of imaging and genetic diagnosis
  210. Pathogenic bacteria and treatment resistance in older cardiovascular disease patients with lung infection and risk prediction model
  211. Adoption value of support vector machine algorithm-based computed tomography imaging in the diagnosis of secondary pulmonary fungal infections in patients with malignant hematological disorders
  212. From slides to insights: Harnessing deep learning for prognostic survival prediction in human colorectal cancer histology
  213. Ecology and Environmental Science
  214. Monitoring of hourly carbon dioxide concentration under different land use types in arid ecosystem
  215. Comparing the differences of prokaryotic microbial community between pit walls and bottom from Chinese liquor revealed by 16S rRNA gene sequencing
  216. Effects of cadmium stress on fruits germination and growth of two herbage species
  217. Bamboo charcoal affects soil properties and bacterial community in tea plantations
  218. Optimization of biogas potential using kinetic models, response surface methodology, and instrumental evidence for biodegradation of tannery fleshings during anaerobic digestion
  219. Understory vegetation diversity patterns of Platycladus orientalis and Pinus elliottii communities in Central and Southern China
  220. Studies on macrofungi diversity and discovery of new species of Abortiporus from Baotianman World Biosphere Reserve
  221. Food Science
  222. Effect of berrycactus fruit (Myrtillocactus geometrizans) on glutamate, glutamine, and GABA levels in the frontal cortex of rats fed with a high-fat diet
  223. Guesstimate of thymoquinone diversity in Nigella sativa L. genotypes and elite varieties collected from Indian states using HPTLC technique
  224. Analysis of bacterial community structure of Fuzhuan tea with different processing techniques
  225. Untargeted metabolomics reveals sour jujube kernel benefiting the nutritional value and flavor of Morchella esculenta
  226. Mycobiota in Slovak wine grapes: A case study from the small Carpathians wine region
  227. Elemental analysis of Fadogia ancylantha leaves used as a nutraceutical in Mashonaland West Province, Zimbabwe
  228. Microbiological transglutaminase: Biotechnological application in the food industry
  229. Influence of solvent-free extraction of fish oil from catfish (Clarias magur) heads using a Taguchi orthogonal array design: A qualitative and quantitative approach
  230. Chromatographic analysis of the chemical composition and anticancer activities of Curcuma longa extract cultivated in Palestine
  231. The potential for the use of leghemoglobin and plant ferritin as sources of iron
  232. Investigating the association between dietary patterns and glycemic control among children and adolescents with T1DM
  233. Bioengineering and Biotechnology
  234. Biocompatibility and osteointegration capability of β-TCP manufactured by stereolithography 3D printing: In vitro study
  235. Clinical characteristics and the prognosis of diabetic foot in Tibet: A single center, retrospective study
  236. Agriculture
  237. Biofertilizer and NPSB fertilizer application effects on nodulation and productivity of common bean (Phaseolus vulgaris L.) at Sodo Zuria, Southern Ethiopia
  238. On correlation between canopy vegetation and growth indexes of maize varieties with different nitrogen efficiencies
  239. Exopolysaccharides from Pseudomonas tolaasii inhibit the growth of Pleurotus ostreatus mycelia
  240. A transcriptomic evaluation of the mechanism of programmed cell death of the replaceable bud in Chinese chestnut
  241. Melatonin enhances salt tolerance in sorghum by modulating photosynthetic performance, osmoregulation, antioxidant defense, and ion homeostasis
  242. Effects of plant density on alfalfa (Medicago sativa L.) seed yield in western Heilongjiang areas
  243. Identification of rice leaf diseases and deficiency disorders using a novel DeepBatch technique
  244. Artificial intelligence and internet of things oriented sustainable precision farming: Towards modern agriculture
  245. Animal Sciences
  246. Effect of ketogenic diet on exercise tolerance and transcriptome of gastrocnemius in mice
  247. Combined analysis of mRNA–miRNA from testis tissue in Tibetan sheep with different FecB genotypes
  248. Isolation, identification, and drug resistance of a partially isolated bacterium from the gill of Siniperca chuatsi
  249. Tracking behavioral changes of confined sows from the first mating to the third parity
  250. The sequencing of the key genes and end products in the TLR4 signaling pathway from the kidney of Rana dybowskii exposed to Aeromonas hydrophila
  251. Development of a new candidate vaccine against piglet diarrhea caused by Escherichia coli
  252. Plant Sciences
  253. Crown and diameter structure of pure Pinus massoniana Lamb. forest in Hunan province, China
  254. Genetic evaluation and germplasm identification analysis on ITS2, trnL-F, and psbA-trnH of alfalfa varieties germplasm resources
  255. Tissue culture and rapid propagation technology for Gentiana rhodantha
  256. Effects of cadmium on the synthesis of active ingredients in Salvia miltiorrhiza
  257. Cloning and expression analysis of VrNAC13 gene in mung bean
  258. Chlorate-induced molecular floral transition revealed by transcriptomes
  259. Effects of warming and drought on growth and development of soybean in Hailun region
  260. Effects of different light conditions on transient expression and biomass in Nicotiana benthamiana leaves
  261. Comparative analysis of the rhizosphere microbiome and medicinally active ingredients of Atractylodes lancea from different geographical origins
  262. Distinguish Dianthus species or varieties based on chloroplast genomes
  263. Comparative transcriptomes reveal molecular mechanisms of apple blossoms of different tolerance genotypes to chilling injury
  264. Study on fresh processing key technology and quality influence of Cut Ophiopogonis Radix based on multi-index evaluation
  265. An advanced approach for fig leaf disease detection and classification: Leveraging image processing and enhanced support vector machine methodology
  266. Erratum
  267. Erratum to “Protein Z modulates the metastasis of lung adenocarcinoma cells”
  268. Erratum to “BRCA1 subcellular localization regulated by PI3K signaling pathway in triple-negative breast cancer MDA-MB-231 cells and hormone-sensitive T47D cells”
  269. Retraction
  270. Retraction to “Protocatechuic acid attenuates cerebral aneurysm formation and progression by inhibiting TNF-alpha/Nrf-2/NF-kB-mediated inflammatory mechanisms in experimental rats”
https://doi.org/10.1515/biol-2022-0721
Schlagwörter für diesen Artikel
tannery fleshings; proteolytic enzymes; biogas; kinetics and instrumental analysis
Creative Commons
BY 4.0

Artikel in diesem Heft

  1. Biomedical Sciences
  2. Systemic investigation of inetetamab in combination with small molecules to treat HER2-overexpressing breast and gastric cancers
  3. Immunosuppressive treatment for idiopathic membranous nephropathy: An updated network meta-analysis
  4. Identifying two pathogenic variants in a patient with pigmented paravenous retinochoroidal atrophy
  5. Effects of phytoestrogens combined with cold stress on sperm parameters and testicular proteomics in rats
  6. A case of pulmonary embolism with bad warfarin anticoagulant effects caused by E. coli infection
  7. Neutrophilia with subclinical Cushing’s disease: A case report and literature review
  8. Isoimperatorin alleviates lipopolysaccharide-induced periodontitis by downregulating ERK1/2 and NF-κB pathways
  9. Immunoregulation of synovial macrophages for the treatment of osteoarthritis
  10. Novel CPLANE1 c.8948dupT (p.P2984Tfs*7) variant in a child patient with Joubert syndrome
  11. Antiphospholipid antibodies and the risk of thrombosis in myeloproliferative neoplasms
  12. Immunological responses of septic rats to combination therapy with thymosin α1 and vitamin C
  13. High glucose and high lipid induced mitochondrial dysfunction in JEG-3 cells through oxidative stress
  14. Pharmacological inhibition of the ubiquitin-specific protease 8 effectively suppresses glioblastoma cell growth
  15. Levocarnitine regulates the growth of angiotensin II-induced myocardial fibrosis cells via TIMP-1
  16. Age-related changes in peripheral T-cell subpopulations in elderly individuals: An observational study
  17. Single-cell transcription analysis reveals the tumor origin and heterogeneity of human bilateral renal clear cell carcinoma
  18. Identification of iron metabolism-related genes as diagnostic signatures in sepsis by blood transcriptomic analysis
  19. Long noncoding RNA ACART knockdown decreases 3T3-L1 preadipocyte proliferation and differentiation
  20. Surgery, adjuvant immunotherapy plus chemotherapy and radiotherapy for primary malignant melanoma of the parotid gland (PGMM): A case report
  21. Dosimetry comparison with helical tomotherapy, volumetric modulated arc therapy, and intensity-modulated radiotherapy for grade II gliomas: A single‑institution case series
  22. Soy isoflavone reduces LPS-induced acute lung injury via increasing aquaporin 1 and aquaporin 5 in rats
  23. Refractory hypokalemia with sexual dysplasia and infertility caused by 17α-hydroxylase deficiency and triple X syndrome: A case report
  24. Meta-analysis of cancer risk among end stage renal disease undergoing maintenance dialysis
  25. 6-Phosphogluconate dehydrogenase inhibition arrests growth and induces apoptosis in gastric cancer via AMPK activation and oxidative stress
  26. Experimental study on the optimization of ANM33 release in foam cells
  27. Primary retroperitoneal angiosarcoma: A case report
  28. Metabolomic analysis-identified 2-hydroxybutyric acid might be a key metabolite of severe preeclampsia
  29. Malignant pleural effusion diagnosis and therapy
  30. Effect of spaceflight on the phenotype and proteome of Escherichia coli
  31. Comparison of immunotherapy combined with stereotactic radiotherapy and targeted therapy for patients with brain metastases: A systemic review and meta-analysis
  32. Activation of hypermethylated P2RY1 mitigates gastric cancer by promoting apoptosis and inhibiting proliferation
  33. Association between the VEGFR-2 -604T/C polymorphism (rs2071559) and type 2 diabetic retinopathy
  34. The role of IL-31 and IL-34 in the diagnosis and treatment of chronic periodontitis
  35. Triple-negative mouse breast cancer initiating cells show high expression of beta1 integrin and increased malignant features
  36. mNGS facilitates the accurate diagnosis and antibiotic treatment of suspicious critical CNS infection in real practice: A retrospective study
  37. The apatinib and pemetrexed combination has antitumor and antiangiogenic effects against NSCLC
  38. Radiotherapy for primary thyroid adenoid cystic carcinoma
  39. Design and functional preliminary investigation of recombinant antigen EgG1Y162–EgG1Y162 against Echinococcus granulosus
  40. Effects of losartan in patients with NAFLD: A meta-analysis of randomized controlled trial
  41. Bibliometric analysis of METTL3: Current perspectives, highlights, and trending topics
  42. Performance comparison of three scaling algorithms in NMR-based metabolomics analysis
  43. PI3K/AKT/mTOR pathway and its related molecules participate in PROK1 silence-induced anti-tumor effects on pancreatic cancer
  44. The altered expression of cytoskeletal and synaptic remodeling proteins during epilepsy
  45. Effects of pegylated recombinant human granulocyte colony-stimulating factor on lymphocytes and white blood cells of patients with malignant tumor
  46. Prostatitis as initial manifestation of Chlamydia psittaci pneumonia diagnosed by metagenome next-generation sequencing: A case report
  47. NUDT21 relieves sevoflurane-induced neurological damage in rats by down-regulating LIMK2
  48. Association of interleukin-10 rs1800896, rs1800872, and interleukin-6 rs1800795 polymorphisms with squamous cell carcinoma risk: A meta-analysis
  49. Exosomal HBV-DNA for diagnosis and treatment monitoring of chronic hepatitis B
  50. Shear stress leads to the dysfunction of endothelial cells through the Cav-1-mediated KLF2/eNOS/ERK signaling pathway under physiological conditions
  51. Interaction between the PI3K/AKT pathway and mitochondrial autophagy in macrophages and the leukocyte count in rats with LPS-induced pulmonary infection
  52. Meta-analysis of the rs231775 locus polymorphism in the CTLA-4 gene and the susceptibility to Graves’ disease in children
  53. Cloning, subcellular localization and expression of phosphate transporter gene HvPT6 of hulless barley
  54. Coptisine mitigates diabetic nephropathy via repressing the NRLP3 inflammasome
  55. Significant elevated CXCL14 and decreased IL-39 levels in patients with tuberculosis
  56. Whole-exome sequencing applications in prenatal diagnosis of fetal bowel dilatation
  57. Gemella morbillorum infective endocarditis: A case report and literature review
  58. An unusual ectopic thymoma clonal evolution analysis: A case report
  59. Severe cumulative skin toxicity during toripalimab combined with vemurafenib following toripalimab alone
  60. Detection of V. vulnificus septic shock with ARDS using mNGS
  61. Novel rare genetic variants of familial and sporadic pulmonary atresia identified by whole-exome sequencing
  62. The influence and mechanistic action of sperm DNA fragmentation index on the outcomes of assisted reproduction technology
  63. Novel compound heterozygous mutations in TELO2 in an infant with You-Hoover-Fong syndrome: A case report and literature review
  64. ctDNA as a prognostic biomarker in resectable CLM: Systematic review and meta-analysis
  65. Diagnosis of primary amoebic meningoencephalitis by metagenomic next-generation sequencing: A case report
  66. Phylogenetic analysis of promoter regions of human Dolichol kinase (DOLK) and orthologous genes using bioinformatics tools
  67. Collagen changes in rabbit conjunctiva after conjunctival crosslinking
  68. Effects of NM23 transfection of human gastric carcinoma cells in mice
  69. Oral nifedipine and phytosterol, intravenous nicardipine, and oral nifedipine only: Three-arm, retrospective, cohort study for management of severe preeclampsia
  70. Case report of hepatic retiform hemangioendothelioma: A rare tumor treated with ultrasound-guided microwave ablation
  71. Curcumin induces apoptosis in human hepatocellular carcinoma cells by decreasing the expression of STAT3/VEGF/HIF-1α signaling
  72. Rare presentation of double-clonal Waldenström macroglobulinemia with pulmonary embolism: A case report
  73. Giant duplication of the transverse colon in an adult: A case report and literature review
  74. Ectopic thyroid tissue in the breast: A case report
  75. SDR16C5 promotes proliferation and migration and inhibits apoptosis in pancreatic cancer
  76. Vaginal metastasis from breast cancer: A case report
  77. Screening of the best time window for MSC transplantation to treat acute myocardial infarction with SDF-1α antibody-loaded targeted ultrasonic microbubbles: An in vivo study in miniswine
  78. Inhibition of TAZ impairs the migration ability of melanoma cells
  79. Molecular complexity analysis of the diagnosis of Gitelman syndrome in China
  80. Effects of maternal calcium and protein intake on the development and bone metabolism of offspring mice
  81. Identification of winter wheat pests and diseases based on improved convolutional neural network
  82. Ultra-multiplex PCR technique to guide treatment of Aspergillus-infected aortic valve prostheses
  83. Virtual high-throughput screening: Potential inhibitors targeting aminopeptidase N (CD13) and PIKfyve for SARS-CoV-2
  84. Immune checkpoint inhibitors in cancer patients with COVID-19
  85. Utility of methylene blue mixed with autologous blood in preoperative localization of pulmonary nodules and masses
  86. Integrated analysis of the microbiome and transcriptome in stomach adenocarcinoma
  87. Berberine suppressed sarcopenia insulin resistance through SIRT1-mediated mitophagy
  88. DUSP2 inhibits the progression of lupus nephritis in mice by regulating the STAT3 pathway
  89. Lung abscess by Fusobacterium nucleatum and Streptococcus spp. co-infection by mNGS: A case series
  90. Genetic alterations of KRAS and TP53 in intrahepatic cholangiocarcinoma associated with poor prognosis
  91. Granulomatous polyangiitis involving the fourth ventricle: Report of a rare case and a literature review
  92. Studying infant mortality: A demographic analysis based on data mining models
  93. Metaplastic breast carcinoma with osseous differentiation: A report of a rare case and literature review
  94. Protein Z modulates the metastasis of lung adenocarcinoma cells
  95. Inhibition of pyroptosis and apoptosis by capsaicin protects against LPS-induced acute kidney injury through TRPV1/UCP2 axis in vitro
  96. TAK-242, a toll-like receptor 4 antagonist, against brain injury by alleviates autophagy and inflammation in rats
  97. Primary mediastinum Ewing’s sarcoma with pleural effusion: A case report and literature review
  98. Association of ADRB2 gene polymorphisms and intestinal microbiota in Chinese Han adolescents
  99. Tanshinone IIA alleviates chondrocyte apoptosis and extracellular matrix degeneration by inhibiting ferroptosis
  100. Study on the cytokines related to SARS-Cov-2 in testicular cells and the interaction network between cells based on scRNA-seq data
  101. Effect of periostin on bone metabolic and autophagy factors during tooth eruption in mice
  102. HP1 induces ferroptosis of renal tubular epithelial cells through NRF2 pathway in diabetic nephropathy
  103. Intravaginal estrogen management in postmenopausal patients with vaginal squamous intraepithelial lesions along with CO2 laser ablation: A retrospective study
  104. Hepatocellular carcinoma cell differentiation trajectory predicts immunotherapy, potential therapeutic drugs, and prognosis of patients
  105. Effects of physical exercise on biomarkers of oxidative stress in healthy subjects: A meta-analysis of randomized controlled trials
  106. Identification of lysosome-related genes in connection with prognosis and immune cell infiltration for drug candidates in head and neck cancer
  107. Development of an instrument-free and low-cost ELISA dot-blot test to detect antibodies against SARS-CoV-2
  108. Research progress on gas signal molecular therapy for Parkinson’s disease
  109. Adiponectin inhibits TGF-β1-induced skin fibroblast proliferation and phenotype transformation via the p38 MAPK signaling pathway
  110. The G protein-coupled receptor-related gene signatures for predicting prognosis and immunotherapy response in bladder urothelial carcinoma
  111. α-Fetoprotein contributes to the malignant biological properties of AFP-producing gastric cancer
  112. CXCL12/CXCR4/CXCR7 axis in placenta tissues of patients with placenta previa
  113. Association between thyroid stimulating hormone levels and papillary thyroid cancer risk: A meta-analysis
  114. Significance of sTREM-1 and sST2 combined diagnosis for sepsis detection and prognosis prediction
  115. Diagnostic value of serum neuroactive substances in the acute exacerbation of chronic obstructive pulmonary disease complicated with depression
  116. Research progress of AMP-activated protein kinase and cardiac aging
  117. TRIM29 knockdown prevented the colon cancer progression through decreasing the ubiquitination levels of KRT5
  118. Cross-talk between gut microbiota and liver steatosis: Complications and therapeutic target
  119. Metastasis from small cell lung cancer to ovary: A case report
  120. The early diagnosis and pathogenic mechanisms of sepsis-related acute kidney injury
  121. The effect of NK cell therapy on sepsis secondary to lung cancer: A case report
  122. Erianin alleviates collagen-induced arthritis in mice by inhibiting Th17 cell differentiation
  123. Loss of ACOX1 in clear cell renal cell carcinoma and its correlation with clinical features
  124. Signalling pathways in the osteogenic differentiation of periodontal ligament stem cells
  125. Crosstalk between lactic acid and immune regulation and its value in the diagnosis and treatment of liver failure
  126. Clinicopathological features and differential diagnosis of gastric pleomorphic giant cell carcinoma
  127. Traumatic brain injury and rTMS-ERPs: Case report and literature review
  128. Extracellular fibrin promotes non-small cell lung cancer progression through integrin β1/PTEN/AKT signaling
  129. Knockdown of DLK4 inhibits non-small cell lung cancer tumor growth by downregulating CKS2
  130. The co-expression pattern of VEGFR-2 with indicators related to proliferation, apoptosis, and differentiation of anagen hair follicles
  131. Inflammation-related signaling pathways in tendinopathy
  132. CD4+ T cell count in HIV/TB co-infection and co-occurrence with HL: Case report and literature review
  133. Clinical analysis of severe Chlamydia psittaci pneumonia: Case series study
  134. Bioinformatics analysis to identify potential biomarkers for the pulmonary artery hypertension associated with the basement membrane
  135. Influence of MTHFR polymorphism, alone or in combination with smoking and alcohol consumption, on cancer susceptibility
  136. Catharanthus roseus (L.) G. Don counteracts the ampicillin resistance in multiple antibiotic-resistant Staphylococcus aureus by downregulation of PBP2a synthesis
  137. Combination of a bronchogenic cyst in the thoracic spinal canal with chronic myelocytic leukemia
  138. Bacterial lipoprotein plays an important role in the macrophage autophagy and apoptosis induced by Salmonella typhimurium and Staphylococcus aureus
  139. TCL1A+ B cells predict prognosis in triple-negative breast cancer through integrative analysis of single-cell and bulk transcriptomic data
  140. Ezrin promotes esophageal squamous cell carcinoma progression via the Hippo signaling pathway
  141. Ferroptosis: A potential target of macrophages in plaque vulnerability
  142. Predicting pediatric Crohn's disease based on six mRNA-constructed risk signature using comprehensive bioinformatic approaches
  143. Applications of genetic code expansion and photosensitive UAAs in studying membrane proteins
  144. HK2 contributes to the proliferation, migration, and invasion of diffuse large B-cell lymphoma cells by enhancing the ERK1/2 signaling pathway
  145. IL-17 in osteoarthritis: A narrative review
  146. Circadian cycle and neuroinflammation
  147. Probiotic management and inflammatory factors as a novel treatment in cirrhosis: A systematic review and meta-analysis
  148. Hemorrhagic meningioma with pulmonary metastasis: Case report and literature review
  149. SPOP regulates the expression profiles and alternative splicing events in human hepatocytes
  150. Knockdown of SETD5 inhibited glycolysis and tumor growth in gastric cancer cells by down-regulating Akt signaling pathway
  151. PTX3 promotes IVIG resistance-induced endothelial injury in Kawasaki disease by regulating the NF-κB pathway
  152. Pancreatic ectopic thyroid tissue: A case report and analysis of literature
  153. The prognostic impact of body mass index on female breast cancer patients in underdeveloped regions of northern China differs by menopause status and tumor molecular subtype
  154. Report on a case of liver-originating malignant melanoma of unknown primary
  155. Case report: Herbal treatment of neutropenic enterocolitis after chemotherapy for breast cancer
  156. The fibroblast growth factor–Klotho axis at molecular level
  157. Characterization of amiodarone action on currents in hERG-T618 gain-of-function mutations
  158. A case report of diagnosis and dynamic monitoring of Listeria monocytogenes meningitis with NGS
  159. Effect of autologous platelet-rich plasma on new bone formation and viability of a Marburg bone graft
  160. Small breast epithelial mucin as a useful prognostic marker for breast cancer patients
  161. Continuous non-adherent culture promotes transdifferentiation of human adipose-derived stem cells into retinal lineage
  162. Nrf3 alleviates oxidative stress and promotes the survival of colon cancer cells by activating AKT/BCL-2 signal pathway
  163. Favorable response to surufatinib in a patient with necrolytic migratory erythema: A case report
  164. Case report of atypical undernutrition of hypoproteinemia type
  165. Down-regulation of COL1A1 inhibits tumor-associated fibroblast activation and mediates matrix remodeling in the tumor microenvironment of breast cancer
  166. Sarcoma protein kinase inhibition alleviates liver fibrosis by promoting hepatic stellate cells ferroptosis
  167. Research progress of serum eosinophil in chronic obstructive pulmonary disease and asthma
  168. Clinicopathological characteristics of co-existing or mixed colorectal cancer and neuroendocrine tumor: Report of five cases
  169. Role of menopausal hormone therapy in the prevention of postmenopausal osteoporosis
  170. Precisional detection of lymph node metastasis using tFCM in colorectal cancer
  171. Advances in diagnosis and treatment of perimenopausal syndrome
  172. A study of forensic genetics: ITO index distribution and kinship judgment between two individuals
  173. Acute lupus pneumonitis resembling miliary tuberculosis: A case-based review
  174. Plasma levels of CD36 and glutathione as biomarkers for ruptured intracranial aneurysm
  175. Fractalkine modulates pulmonary angiogenesis and tube formation by modulating CX3CR1 and growth factors in PVECs
  176. Novel risk prediction models for deep vein thrombosis after thoracotomy and thoracoscopic lung cancer resections, involving coagulation and immune function
  177. Exploring the diagnostic markers of essential tremor: A study based on machine learning algorithms
  178. Evaluation of effects of small-incision approach treatment on proximal tibia fracture by deep learning algorithm-based magnetic resonance imaging
  179. An online diagnosis method for cancer lesions based on intelligent imaging analysis
  180. Medical imaging in rheumatoid arthritis: A review on deep learning approach
  181. Predictive analytics in smart healthcare for child mortality prediction using a machine learning approach
  182. Utility of neutrophil–lymphocyte ratio and platelet–lymphocyte ratio in predicting acute-on-chronic liver failure survival
  183. A biomedical decision support system for meta-analysis of bilateral upper-limb training in stroke patients with hemiplegia
  184. TNF-α and IL-8 levels are positively correlated with hypobaric hypoxic pulmonary hypertension and pulmonary vascular remodeling in rats
  185. Stochastic gradient descent optimisation for convolutional neural network for medical image segmentation
  186. Comparison of the prognostic value of four different critical illness scores in patients with sepsis-induced coagulopathy
  187. Application and teaching of computer molecular simulation embedded technology and artificial intelligence in drug research and development
  188. Hepatobiliary surgery based on intelligent image segmentation technology
  189. Value of brain injury-related indicators based on neural network in the diagnosis of neonatal hypoxic-ischemic encephalopathy
  190. Analysis of early diagnosis methods for asymmetric dementia in brain MR images based on genetic medical technology
  191. Early diagnosis for the onset of peri-implantitis based on artificial neural network
  192. Clinical significance of the detection of serum IgG4 and IgG4/IgG ratio in patients with thyroid-associated ophthalmopathy
  193. Forecast of pain degree of lumbar disc herniation based on back propagation neural network
  194. SPA-UNet: A liver tumor segmentation network based on fused multi-scale features
  195. Systematic evaluation of clinical efficacy of CYP1B1 gene polymorphism in EGFR mutant non-small cell lung cancer observed by medical image
  196. Rehabilitation effect of intelligent rehabilitation training system on hemiplegic limb spasms after stroke
  197. A novel approach for minimising anti-aliasing effects in EEG data acquisition
  198. ErbB4 promotes M2 activation of macrophages in idiopathic pulmonary fibrosis
  199. Clinical role of CYP1B1 gene polymorphism in prediction of postoperative chemotherapy efficacy in NSCLC based on individualized health model
  200. Lung nodule segmentation via semi-residual multi-resolution neural networks
  201. Evaluation of brain nerve function in ICU patients with Delirium by deep learning algorithm-based resting state MRI
  202. A data mining technique for detecting malignant mesothelioma cancer using multiple regression analysis
  203. Markov model combined with MR diffusion tensor imaging for predicting the onset of Alzheimer’s disease
  204. Effectiveness of the treatment of depression associated with cancer and neuroimaging changes in depression-related brain regions in patients treated with the mediator-deuterium acupuncture method
  205. Molecular mechanism of colorectal cancer and screening of molecular markers based on bioinformatics analysis
  206. Monitoring and evaluation of anesthesia depth status data based on neuroscience
  207. Exploring the conformational dynamics and thermodynamics of EGFR S768I and G719X + S768I mutations in non-small cell lung cancer: An in silico approaches
  208. Optimised feature selection-driven convolutional neural network using gray level co-occurrence matrix for detection of cervical cancer
  209. Incidence of different pressure patterns of spinal cerebellar ataxia and analysis of imaging and genetic diagnosis
  210. Pathogenic bacteria and treatment resistance in older cardiovascular disease patients with lung infection and risk prediction model
  211. Adoption value of support vector machine algorithm-based computed tomography imaging in the diagnosis of secondary pulmonary fungal infections in patients with malignant hematological disorders
  212. From slides to insights: Harnessing deep learning for prognostic survival prediction in human colorectal cancer histology
  213. Ecology and Environmental Science
  214. Monitoring of hourly carbon dioxide concentration under different land use types in arid ecosystem
  215. Comparing the differences of prokaryotic microbial community between pit walls and bottom from Chinese liquor revealed by 16S rRNA gene sequencing
  216. Effects of cadmium stress on fruits germination and growth of two herbage species
  217. Bamboo charcoal affects soil properties and bacterial community in tea plantations
  218. Optimization of biogas potential using kinetic models, response surface methodology, and instrumental evidence for biodegradation of tannery fleshings during anaerobic digestion
  219. Understory vegetation diversity patterns of Platycladus orientalis and Pinus elliottii communities in Central and Southern China
  220. Studies on macrofungi diversity and discovery of new species of Abortiporus from Baotianman World Biosphere Reserve
  221. Food Science
  222. Effect of berrycactus fruit (Myrtillocactus geometrizans) on glutamate, glutamine, and GABA levels in the frontal cortex of rats fed with a high-fat diet
  223. Guesstimate of thymoquinone diversity in Nigella sativa L. genotypes and elite varieties collected from Indian states using HPTLC technique
  224. Analysis of bacterial community structure of Fuzhuan tea with different processing techniques
  225. Untargeted metabolomics reveals sour jujube kernel benefiting the nutritional value and flavor of Morchella esculenta
  226. Mycobiota in Slovak wine grapes: A case study from the small Carpathians wine region
  227. Elemental analysis of Fadogia ancylantha leaves used as a nutraceutical in Mashonaland West Province, Zimbabwe
  228. Microbiological transglutaminase: Biotechnological application in the food industry
  229. Influence of solvent-free extraction of fish oil from catfish (Clarias magur) heads using a Taguchi orthogonal array design: A qualitative and quantitative approach
  230. Chromatographic analysis of the chemical composition and anticancer activities of Curcuma longa extract cultivated in Palestine
  231. The potential for the use of leghemoglobin and plant ferritin as sources of iron
  232. Investigating the association between dietary patterns and glycemic control among children and adolescents with T1DM
  233. Bioengineering and Biotechnology
  234. Biocompatibility and osteointegration capability of β-TCP manufactured by stereolithography 3D printing: In vitro study
  235. Clinical characteristics and the prognosis of diabetic foot in Tibet: A single center, retrospective study
  236. Agriculture
  237. Biofertilizer and NPSB fertilizer application effects on nodulation and productivity of common bean (Phaseolus vulgaris L.) at Sodo Zuria, Southern Ethiopia
  238. On correlation between canopy vegetation and growth indexes of maize varieties with different nitrogen efficiencies
  239. Exopolysaccharides from Pseudomonas tolaasii inhibit the growth of Pleurotus ostreatus mycelia
  240. A transcriptomic evaluation of the mechanism of programmed cell death of the replaceable bud in Chinese chestnut
  241. Melatonin enhances salt tolerance in sorghum by modulating photosynthetic performance, osmoregulation, antioxidant defense, and ion homeostasis
  242. Effects of plant density on alfalfa (Medicago sativa L.) seed yield in western Heilongjiang areas
  243. Identification of rice leaf diseases and deficiency disorders using a novel DeepBatch technique
  244. Artificial intelligence and internet of things oriented sustainable precision farming: Towards modern agriculture
  245. Animal Sciences
  246. Effect of ketogenic diet on exercise tolerance and transcriptome of gastrocnemius in mice
  247. Combined analysis of mRNA–miRNA from testis tissue in Tibetan sheep with different FecB genotypes
  248. Isolation, identification, and drug resistance of a partially isolated bacterium from the gill of Siniperca chuatsi
  249. Tracking behavioral changes of confined sows from the first mating to the third parity
  250. The sequencing of the key genes and end products in the TLR4 signaling pathway from the kidney of Rana dybowskii exposed to Aeromonas hydrophila
  251. Development of a new candidate vaccine against piglet diarrhea caused by Escherichia coli
  252. Plant Sciences
  253. Crown and diameter structure of pure Pinus massoniana Lamb. forest in Hunan province, China
  254. Genetic evaluation and germplasm identification analysis on ITS2, trnL-F, and psbA-trnH of alfalfa varieties germplasm resources
  255. Tissue culture and rapid propagation technology for Gentiana rhodantha
  256. Effects of cadmium on the synthesis of active ingredients in Salvia miltiorrhiza
  257. Cloning and expression analysis of VrNAC13 gene in mung bean
  258. Chlorate-induced molecular floral transition revealed by transcriptomes
  259. Effects of warming and drought on growth and development of soybean in Hailun region
  260. Effects of different light conditions on transient expression and biomass in Nicotiana benthamiana leaves
  261. Comparative analysis of the rhizosphere microbiome and medicinally active ingredients of Atractylodes lancea from different geographical origins
  262. Distinguish Dianthus species or varieties based on chloroplast genomes
  263. Comparative transcriptomes reveal molecular mechanisms of apple blossoms of different tolerance genotypes to chilling injury
  264. Study on fresh processing key technology and quality influence of Cut Ophiopogonis Radix based on multi-index evaluation
  265. An advanced approach for fig leaf disease detection and classification: Leveraging image processing and enhanced support vector machine methodology
  266. Erratum
  267. Erratum to “Protein Z modulates the metastasis of lung adenocarcinoma cells”
  268. Erratum to “BRCA1 subcellular localization regulated by PI3K signaling pathway in triple-negative breast cancer MDA-MB-231 cells and hormone-sensitive T47D cells”
  269. Retraction
  270. Retraction to “Protocatechuic acid attenuates cerebral aneurysm formation and progression by inhibiting TNF-alpha/Nrf-2/NF-kB-mediated inflammatory mechanisms in experimental rats”
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© 2025 De Gruyter Brill
Heruntergeladen am 6.9.2025 von https://www.degruyterbrill.com/document/doi/10.1515/biol-2022-0721/html
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