Band 5, Heft 2

This paper examines the performance results of configured semi-continuous mesophilic bioreactors for methane fermentation of pretreated wheat straw co-digested with cattle manure. The semi-continuous process was carried out in three different types of bioreactors, i.e. continuous stirred tank reactor (CSTR), fixed film reactor (FFR), and conventional floating drum reactor (CR), with an organic loading rate of 2.2 kg of volatile solids (VS)/day. The observed results revealed that the configuration of the FFR increased the methane production yield by 41.1%. However, the configuration of the CSTR had only a marginal effect on enhancement of methane production yield (yield increased only by 10.6%) compared to the CR. The VS removal for digesters did not vary much at the same organic loading rate. The study revealed that the pretreated wheat straw with the FFR had yield methane production of 0.342 m 3 /kg VS, whereas the CSTR and CR had yield methane production of 0.289 m 3 /kg VS and 0.264 m 3 /kg VS, respectively.

In the search of new materials for developing clean catalytic organic reactions, our team engineered graphene based palladium (Pd) nanocomposites and tested them as catalysts for ionic liquid mediated Suzuki cross coupling reaction. The effects of various reaction parameters, such as solvent, base, time and temperature, were investigated for the Suzuki reaction. The optimized protocol was applied to a wide range of substituted aryl/hetroaryl halides along with various aryl boronic acids and afforded the corresponding reaction products in good to excellent yield. The proposed Pd/reduced graphene oxide (rGO) catalyzed Suzuki reaction protocol was also exploited for the synthesis of unique indazole derivatives. The developed catalytic system circumvents the use of phosphine ligands, with an added advantage of easy Pd catalyst recovery up to eight times.

Asymmetric reduction of ketones is an important transformation in organic synthesis, because chiral carbinols are useful bioactive compounds. In this study, bioreduction of acetophenone (ACP) for production of enantiomerically pure (S)-1-phenyl-ethanol was investigated and freeze-dried carrots were used as a source of alcohol dehydrogenases (ADHs). However, production of product was investigated systematically using response surface methodology (RSM). Before RSM, the effects of the initial substrate concentration, reaction time, temperature and pH on the bioreduction were studied. The best results for enantiomeric excesses (ee) and conversion (c) were obtained with >99% and 58%, respectively, for the reaction time 48 h, initial substrate concentration 1 m m , reaction temperature 33°C and pH 7. In the RSM, initial substrate concentration, concentration of plant cell, reaction time and stirring rate were chosen as independent variables. The predicted optimum conditions for a higher ee (>99%) and conversion (57.8%) were as follows: initial substrate concentration, 1 m m ; concentration of plant cell, 25 g/l; reaction time, 52 h and stirring rate, 200 rpm. As a result of repeated experiments, the product was obtained as 0.6 m m at this optimum point and the values obtained demonstrated conformity with 0.578 m m value calculated by the model equation.

The synthesis of MoO 3 nanoparticles was done by the electrochemical method by using tetra butyl ammonium bromide (TBAB) as a stabilizer and structure directing agent in acetonitrile (ACN):tetrahydrofuran (THF) (4:1) solvent at a constant current supply of 18 mA/cm 2 . After heating the nanoparticles to 500°C in a muffle furnace, MoO 3 nanorods were obtained. These synthesized MoO 3 nanorods were characterized by UV-visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD) and scanning electron microscopy. The prepared nanorods were used as heterogeneous catalysts for the synthesis of 2-aryl benzothiazole derivatives. This protocol offers several advantages such as a green method, simple work-up procedure, recyclability of the catalyst and excellent product yield in a short reaction time.

Iodocyclization of 2-allylphenols is a suitable method to access furans and dihydrofurans with adequate yields. Several methodologies to iodocyclization are reported in the literature; however, since some data about the conditions are conflicting, a more systematic approach is needed to define the best conditions. In this work, we performed a full 2 2 factorial design to study the influence of solvent (water or EtOH:water (1:9) mixture) and the addition of NaHCO 3 in iodine-promoted cyclization of 2-allylphenols. The results have shown water as the best solvent to be employed in the cyclization of liquid 2-allylphenols, and the presence of NaHCO 3 leads to lower yields. Several examples of 2-iodomethyl-2,3-dihydrobenzofurans preparations are reported using the optimized conditions; however, high yields are only observed when liquid 2-allylphenols were used.

In this study Lactobacillus brevis cells were cultivated and then disrupted using various cell disruption methods to obtain maximal nicotinamide adenine dinucleotide phosphate (NADP(H))-dependent alcohol dehydrogenase (ADH) activity in cell-free extract. Evolutionary operation (EVOP) technique was used to find the optimal cell disruption method. The released ADH in cell-free extract was then used for biotransformation of ( S )-2-hydroxypropiophenone (( S )-2-HPP) to (1 S , 2 S )-1-phenylpropane-1,2-diol ((1 S , 2 S )-1-PPD). Due to high coenzyme cost, the possibility of NADPH regeneration was considered by examining two substrate-coupled regeneration systems, and for that isopropanol and ( R )-1-phenylethanol were used. The enzyme was kinetically characterized, and kinetics of all reactions were determined. Based on kinetic results, mathematical models were developed and were validated in batch reactor. Both regenerating systems successfully shifted the reaction in the desired direction; without coenzyme regeneration, obtained substrate equilibrium conversion was 27.5%, while with coenzyme regeneration by isopropanol oxidation was 99.0% and by ( R )-1-phenylethanol was 70.1%.

The present work deals with the use of ultrasound atomization for the preparation of zinc oxide nanostructures. The focus of the work is to understand the effect of different operating parameters, such as ultrasonic power dissipation, flow rate, concentration, and surface tension, on the final particle morphology obtained during the synthesis. The prepared nanostructures were observed under scanning electron microscope to understand the morphology of the synthesized nanostructures. It was established that the final characteristics of the nanostructures, in terms of shape and size, can be effectively controlled by controlling flow rate, precursor concentration, surface tension, and ultrasonic power dissipation. The droplet size was found to increase with an increase in the flow rate of an aqueous solution of zinc nitrate, ultrasonic power, and decrease in the loading of surfactant (polyvinylpyrrolidone). The present work has clearly established the utility of ultrasound-assisted synthesis of nanoparticles with clear evidence for obtaining desired characteristics based on controlled application.

In the present work, silver nanoparticles were synthesized using an easy, simple, and environment-friendly method based on principles of green chemistry in the absence of a sophisticated laboratory, and their anti-cancer properties were studied. Silver nanoparticles were synthesized using electrolytic deposition. As-synthesized nanoparticles were capped using black tea leaf extract. MTT assay was used to investigate anti-cancer activity. X-ray diffraction graphs show highly pure as-synthesized silver nanoparticles. Transmission electron microscopy images show well-dispersed spherical nanoparticles, with an average size of 9 and 15 nm, corresponding to different values of parameters used in the synthesis. For the MCF-7 cancer cell lines, 100% growth inhibition is obtained. The 50% growth inhibition concentration values against MCF-7 cancer cell lines were obtained at 70- and 30-fold dilutions of colloidal silver of almost the same concentration, 178 μg/ml, for both configurations. Silver nanoparticles can be synthesized, and their morphology can be tuned using the electrolytic deposition method with black tea leaf extract as capping agent. Silver nanoparticles with an average size of 9 nm are more effective those with an average size of 15 nm. The synthesis method is faster, cheaper, and environment friendly and renders a treatment option that can have high accessibility, reduced harmful side effects, and increased economic benefits.

Ultra-fine barium carbonate powders were successfully synthesized using barium chloride dihydrate (BaCl 2 ·2H 2 O), sodium hydroxide (NaOH) and (NH 2 ) 2 CO as raw materials, with the help of different guide reagents, by the homogeneous precipitation method using response surface methodology (RSM) and central composite design (CCD). Their phases of prepared BaCO 3 powders under the optimal conditions were characterized by X-ray powder diffraction (XRD). The characterization results showed that different guide reagents have an effect on the phase structure and composition of products, while they play significant roles in determining the morphology of products. All of the synthesized ultra-fine barium carbonate powders had typical orthorhombic structures, which were well-crystallized.

Silica nanoparticle embedded carbon 2D-nanocomposite material has been synthesized using a green procedure from a blue green alga, Scytonema guyanense , by direct pyrolysis at 600°C under inert atmosphere. The nanocomposite was characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), powder X-ray diffraction and energy dispersive spectroscopy (EDS). Characteristic Si-O-Si vibrational absorptions at ~720 cm -1 , ~790 cm -1 and ~1080 cm -1 attested the occurrence of silica in the nanocomposite material. Transmission electron microscopy (TEM) analysis revealed five-fold multiply twinned quasi spherical silica nanoparticles (~40 nm) embedded in ~3 nm thick carbon nanoflakes. The material exhibited weak luminescence at 340 nm. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging study showed moderate antioxidant activity of the material.

A combined process of carbothermal reduction in vacuum and acid leaching is proposed to produce TiC from titanium bearing blast furnace (BF) slag from Pan Steel in Panzhihua city in China. Thermodynamics calculation shows that TiC can be obtained in the appropriate temperature and pressure range. Moreover, the results of the experiment indicate that TiC can be prepared by the combined process. The optimized parameters include particle size of original slag ideally below 200 mesh, reduction temperature of 1400°C, pressure of 1~10 Pa and mass ratio of slag and reduction (carbon powder) of 100/38. The x value in TiC x increases with increase of reduction degree while the maximum is 0.981. The final x is 0.957 in the pure TiC prepared by the combined process. Silicon and magnesium in the slag can be removed by evaporating, which makes silicon and titanium in the slag separate completely.

Ultrasound assisted three phase partitioning (UATPP) has been explored to intensify the extraction and purification of peroxidase from orange peel ( Citrus sinensis ). UATPP of peroxidase was studied by varying different process parameters such as ammonium sulfate concentration, pH, broth to tertiary butanol (t-butanol) ratio, temperature, ultrasound frequency, ultrasound power and duty cycle. Under optimized conditions, i.e. 50% ammonium sulfate saturation, pH 6, temperature 30°C, broth to t-butanol ratio 1:1.5 (v/v), at 25 kHz frequency and 150 W ultrasonication power with 40% duty cycle, 6 min irradiation time, 24.28 fold purity of peroxidase with 91.84% recovery was been obtained. UATPP resulted in higher purification fold of peroxidase due to enhanced mass transfer with reduced operation time from 80 min to 6 min as compared to conventional three phase partitioning (TPP). SDS PAGE analysis of the partially purified enzyme indicated a molecular weight of 26 kDa. The integration of ultrasound with TPP enhances the utility of both processes. Thus, UATPP has been proved as an efficient alternative to partial purification of peroxidase.

Ziziphus spina-christi L. (ZscL) is a plant residue that has been used as adsorbent for the removal of Hg(II) ions from an aqueous solution. The ability of ZscL to adsorb Hg(II) ions was investigated by using the batch adsorption procedure. It was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) to support the adsorption of Hg(II) ions. The effects of various parameters on the adsorption process, such as contact time, adsorbent concentration, solution pH and initial concentrations of metal ions were studied to optimize the conditions for maximum adsorption. Experimental equilibrium data were fitted to the Freundlich, Langmuir, Dubinin-Radushkevich, Halsey and Temkin (two parameter models), Redlich-Peterson, Sips, Khan, Hill, Radke-Prausnitz, Langmuir-Freundlich and Toth (three parameter models), Fritz-Schlunder and Baudu (four parameter models) and Fritz-Schlunder (five parameter model) at 30°C by using nonlinear regression analysis. The examination of error analysis methods showed that the Halsey model provides the best fit for experimental data compared with the other isotherms. Various kinetic models have been applied to the experimental data to predict the adsorption kinetics. It was found that pseudo-second-order rate was better obeyed than pseudo-first-order reaction, supporting that the chemisorption process was involved. The obtained results show that ZscL can be used as an effective and natural low-cost adsorbent for the removal of Hg(II) ions from aqueous solutions.