Volume 68, Issue 1

This review summarises the high potential of immobilised cells systems for the fermentative production of compounds, mainly produced by representatives of the Clostridium genus. Microorganisms of Clostridium species are recognised as good producers of a wide range of chemicals in almost every sector of industry. The combination of this microorganism with its immobilisation opens up new possibilities and renders the fermentation process more sophisticated than in a free-cell system. This review provides a comprehensive summary of techniques used in immobilisation of Clostridium species with regard to specific products and types of fermentation. In addition, comparisons of particular types of immobilisation techniques used in fermentation processes are summarised by specific products.

Increased need for non-destructive investigation methods in archaeology has become a major issue since sampling is in most cases restricted in view of the importance or uniqueness of the objects. For this reason, preliminary investigation using non-destructive techniques was performed on five samples of amber beads obtained from different excavation and archaeological sites. The use of FTIR and micro-Raman analysis revealed the presence of carboxyl, peroxide, hydroxyl, and complex ester functional groups as well as single and double bonds in the structure of the studied resin varieties. Further analysis of the amber samples from both archaeological and geological types by XPS, XRF, and SEM showed the presence of sulfur and a wide range of trace elements on the surface of the analysed samples. Our results proved that the combination of structural-molecular and surface elemental techniques for amber characterisation provides a very useful and simple methodology for the description of geological and archaeological amber samples from different regions of Europe.

Fused silica capillary columns of the internal diameter of 320 μm were packed with the Nucleosil C18 stationary phase of 5 μm using the slurry packing method. The time of the bed compaction phase, packing pressure, and the use of ultrasound varied to study their influence on the column performance. Van Deemter curves were measured and separation impedance values were calculated in order to assess both separation efficiency and kinetic performance of the columns. Selected columns were tested again after nine months to evaluate the stability of their beds. Separation efficiencies of all columns were similar, but a major difference, caused by the use of ultrasound, was observed in the bed stability. Columns sonicated for 25 minutes during the bed compaction phase exhibited unchanged performance in the course of several months, while the performance of non-sonicated columns decreased.

An analytical multiclass, multi-residue method for the determination of antibiotics in aquaculture products was developed and validated. A fast, cheap, and straightforward extraction procedure followed by liquid chromatography-tandem mass spectrometry analysis was proposed. This method covers 32 antibiotics of different classes, which are frequently used in aquaculture. Three different extraction procedures were compared, and the extraction with acetonitrile (0.1 vol. % formic acid) showed the best results. The selected extraction procedure was validated at four different fortification levels (10 μg kg−1, 25 μg kg−1, 50 μg kg−1, and 100 μg kg−1). Recoveries of the tested antibiotics ranged from 70 % to 120 %, with the relative standard deviation (RSD) of triplicates lower than 20 %. The limits of quantification (LOQ) ranged from 0.062 μg kg−1 to 4.6 μg kg−1, allowing for the analysis of trace levels of these antibiotics in aquaculture products. The method was applied to the analysis of selected antibiotics in fish and shrimp meat available in the Czech market.

Fifteen carbohydrates (d-mannose, d-glucose, d-galactose, methyl-α-d-glucose, l-rhamnose, d-xylose, d-fructose, d-arabinose, dulcitol, mannitol, β-maltose, α-lactose, melibiose, sucrose, and raffinose) and four cyclitols [l-(+)-bornesitol, myo-inositol, per-O-acetyl-1-l-(+)-bornesitol, and quinic acid] were assayed for in vitro ACE inhibition. Of these molecules, per-O-Acetyl-1-l-(+)-bornesitol, quinic acid, methyl-α-d-glucose, d-rhamnose, raffinose, and the disaccharides were determined to be either inactive or weak ACE inhibitors, whereas l-(+)-bornesitol, d-galactose, d-glucose, and myo-inositol exhibited significant ACE inhibition. Molecular docking studies were performed to investigate interactions between active compounds and human ACE (Protein Data Bank, PDB 1O83). The results of various calculations showed that all active sugars bind to the same enzyme region, which is a tunnel directed towards the active site. With the exception of myo-inositol (K i = 13.95 μM, IC50 = 449.2 μM), the active compounds presented similar K i and IC50 values. d-Galactose (K i = 19.6 μM, IC50 = 35.7 μM) and l-(+)-bornesitol (K i = 25.3 μM, IC50 = 41.4 μM) were the most active compounds, followed by d-glucose (K i = 32.9 μM, IC50 = 85.7 μM). Our docking calculations are in agreement with the experimental data and show a new binding region for sugar-like molecules, which may be explored for the development of new ACE inhibitors.

5-Bromo-(Br-PBA) and 3,5-dibromo-2-hydroxy-N-phenylbenzamides (Br2-PBA) inhibited photosynthetic electron transport (PET) and their inhibitory efficiency depended on the compound lipophilicity as well as on the electronic properties of the R substituent in the N-phenyl moiety. Br-PBA showed higher PET inhibiting activity than Br2-PBA with the same R substituent. The most effective inhibitors in the tested series were the derivatives with R = 3-F (Br-PBA; IC50 = 4.3 μmol dm−3) and R = 3-Cl (Br2-PBA; IC50 = 8.6 μmol dm−3). Bilinear dependence of the PET inhibiting activity on the lipophilicity of the compounds as well as on the Hammett constant, σ, of the R substituent was observed for both investigated series. Using EPR spectroscopy it was found that the site of action of the tested compounds in the photosynthetic apparatus is situated on the donor side of PS 2, in D· or in the Z·/D· intermediates. Interaction of the studied compounds with chlorophyll a and aromatic amino acids present in the pigment-protein complexes mainly in photosystem 2 was documented by fluorescence spectroscopy.

Biotransformation of iminodiacetonitrile (IDAN) to iminodiacetic acid (IDA) was investigated with a newly isolated Alcaligenes faecalis ZJUTBX11 strain showing nitrilase activity in the immobilized form. To reduce the mass transfer resistance and to increase the toleration ability of the microorganisms to the toxic substrate as well as to enhance their ability to be reused, encapsulation of the whole cells in alginate-chitosan-alginate (ACA) membrane liquid-core capsules was attempted in the present study. The optimal pH and temperature for nitrilase activity of encapsulated A. faecalis ZJUTBX11 cells were 7.5°C and 35°C, respectively, which is consistent with free cells. Based on the Michaelis-Menten model, kinetic parameters of the conversion reaction with IDAN as the substrate were: K m = (17.6 ± 0.3) mmol L−1 and V max = (97.6 ± 1.2) μmol min−1 g−1 of dry cell mass for encapsulated cells and (16.8 ± 0.4) mmol L−1 and (108.0 ± 2.7) μmol min−1 g−1 of dry cell mass for free cells, respectively. After being recycled ten times, the whole cells encapsulated in ACA capsules still retained 90 % of the initial nitrilase activity while only 35 % were retained by free cells. Lab scale production of IDA using encapsulated cells in a bubble column reactor and a packed bed reactor were performed respectively.

The kinetics of the degradation of metribuzin by water-soluble colloidal MnO2 in acidic medium (HClO4) were studied spectrophotometrically in the absence and presence of surfactants. The experiments were performed under pseudo-first-order reaction conditions in respect of MnO2. The degradation was observed to be of the first order in respect of MnO2 while of fractional order for both metribuzin and HClO4. The rate constant for the degradation of metribuzin was observed to decrease as the concentration of MnO2 increased. The anionic surfactant, sodium dodecyl sulphate (SDS), was observed to be ineffective whereas the non-ionic surfactant, Triton X-100 (TX-100), accelerated the reaction rate. However, the cationic surfactant, cetyltrimethyl ammonium bromide (CTAB), caused flocculation with oppositely-charged colloidal MnO2; hence further study was not possible. The catalytic effect of TX-100 was discussed in the light of the available mathematical model. The kinetic data were exploited to generate the various activation parameters for the oxidative degradation of metribuzin by colloidal MnO2 in the absence as well as the presence of the non-ionic surfactant, TX-100.

Two perpendicular projections of rising bubbles were observed in counter-current downstream diverging flow. Evidently, the bubbles did not enter the boundary layer at the channel wall and a plug liquid flow assumption was acceptable in our experimental equipment. This confirmed that the experiment was appropriate for simulation of bubble rises in a quiescent liquid column. Recent data obtained by a high-speed camera permitted recording over a period of 60 s. Image analysis by a tailor-made program provided a time-series of quantities related to the position, size, and shape of bubbles. In addition to determination of the aspect ratio of the equivalent oblate ellipsoid, deviation from this shape was investigated in respect of the difference between the bubble’s centre of mass and the geometrical centre of bubble projection. Autocorrelation of the data indicated that the bubble inclination oscillated harmonically with a frequency of 5–10 Hz; cross correlation showed that the horizontal shift of the centre of mass, as well as the horizontal velocity, increased with increasing bubble inclination, and the vertical shift of the centre of mass increased with an increases in the absolute value of the bubble inclination. There is no significant phase shift in the oscillation of these quantities. The bulky bottom side of the bubbles is in accordance with the model of bubble oscillation induced by instability of the equilibrium of gravity and surface tension forces. The oscillation frequency dependence on surface forces (Eötvös number) is evident, while viscosity does not play a significant role in low-viscosity liquids. Therefore, vortex-shedding is more likely to be an effect of the oscillation and not its cause.

The enantioselective extraction of 4-nitro-phenylalanine (Nphy) was studied with metal-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) complexes as the chiral selector. The complex with palladium (BINAP-Pd) exhibits the highest selectivity out of the selectors studied, which is solubilised in the organic phase and preferentially extracts d-Nphy from the aqueous phase. Efficiency of extraction depends, often substantially, on a number of process variables, including types of organic solvents and metal precursors, concentration of ligand, pH, and temperature. A reactive extraction model was established to interpret the experimental data. The equilibrium formation constants and other important parameters required by the model were determined experimentally. The equilibrium formation constants were 6.73 and 1.93 for d-Nphy and l-Nphy. By way of modelling and experiment, an optimal extraction condition with pH of 7 and BINAP-Pd concentration of 1 mmol L−1 was obtained with enantioselectivity (α) of 3.37, which was close to the maximum of 3.48, and a performance factor (pf) of 0.195. The model was verified experimentally with excellent results.

A multicell isoperibolic — semiadiabatic calorimeter was used for the measurement of temperature and the determination of the hydration heat evolution at earlier period of cement pastes setting and hardening. The measurements were aimed at the determination of the effect of superplasticizers (SPs) on the course of the Portland cement hydration. Commercial polycarboxylate SP was added to the mixtures and the heat effect was measured. With the increasing content of SP, the hydration temperature increased up to a certain value and then decreased. In case of a sufficient amount of water in the mixture to achieve complete hydration of cement, samples with the highest values of the maximum hydration temperature reached the highest values of the released total heat. If there is not a sufficient amount of water to achieve complete hydration, the samples with the highest values of the maximum hydration temperature reach the lowest values of the released total heat.

Samples of activated bentonite and activated bentonite modified with CuCl and CuCl2, separately, were tested as dimethyl sulfide (DMS) adsorbents. The adsorption and desorption behaviours of DMS on the adsorbents were studied systematically. The adsorbents were characterised by nitrogen adsorption, XRD, and DMS-TPD tests. The addition of CuCl and CuCl2 to the activated carbon significantly enhanced the adsorption capacity of DMS, despite a notable decrease in the specific surface area and total pore volume of the activated bentonite. It is presumed that copper cation species may act as an adsorption site for DMS. The adsorption capacity of Cu(II)-bentonite was better than that of Cu(I)-bentonite. The DMS-TPD patterns indicate that the stronger electrophilicity of Cu(II) compared to that of Cu(I) caused it to interact with the DMS molecules more strongly, thus contributing to a better adsorptive performance. The Cu(II)-bentonite calcined at 150°C had the best DMS removal performance with a high sulphur capacity of 70.56 mg S g−1 adsorbent. The DMS removal performance became much lower with the increase in the calcination temperature, which appeared to be due to the decrease in the CuCl2·2H2O phase and the formation of the monoclinic Cu(OH)Cl phase.

In the present work, kinetics of tartrazine decay by UV irradiation and H2O2 photolysis, and the removal of total organic carbon (TOC) under specific experimental conditions was explored. Irradiation experiments were carried out using a photoreactor of original design with a low-pressure Hg vapour lamp. The photodegradation rate of tartrazine was optimised with respect to the H2O2 concentration and temperature for the constant dye concentration of 1.035 × 10−5 M. Tartrazine degradation and the removal of TOC followed the pseudo-first-order kinetics. The much higher k obs value for tartrazine degradation (7.91 × 10−4 s−1) as compared with the TOC removal (2.3 × 10−4 s−1) confirmed the presence of reaction intermediates in the solution.

Laboratory batch sorption-desorption and column experiments were performed to better understand the effects of microbial exopolymeric substances (EPS) on Cr(III) sorption/desorption rates in the soil-water system. The experiments were carried out in two different modes: one mode (sorption) in which Cr(III) and EPS were applied simultaneously, and the other (desorption) included the sequential application of Cr(III) and EPS to the soil-water system. The batch sorption and desorption experiments showed that, while chromium(III) desorption was significantly enhanced in the presence of EPS relative to non-EPS-containing systems, the desorption rates were much smaller than the sorption rates, and the fraction dissolved by EPS accounted for only a small portion of the total chromium initially sorbed onto soil minerals. Similarly, the column experiments suggested that, while the microbial EPS led to an increase in Cr dissolution relative to non-EPS-containing systems, only a small portion of the total chromium initially added to the soil was mobilised. The differences observed in Cr sorption and desorption rates can be explained through the very low solubility and strong interactions of chromium species with soil minerals as well as the mass transfer effects associated with low diffusion rates. The overall results suggest that, while microbial EPS may play an important role in microbial Cr(VI) treatment in sub-surface systems due to the formation of soluble Cr-EPS complexes, the extent and degree of Cr mobilisation are highly dependent on the type of initial Cr sorption.

The thermal stability (60°C, 80°C, 100°C), antioxidant activity, and ultraviolet C light (UV-C) stability of standard polyphenols solutions (catechin, gallic acid, and vanillic acid) and of vegetal extracts from spruce bark and grape seeds were investigated. Exposure of the standard solutions and vegetal extracts to high temperatures revealed that phenolic compounds were also relatively stable (degradations ranged from 15 % to 30 % after 4 h of exposure). The highest antioxidant activity was obtained for ascorbic acid and gallic acid followed by catechin and caffeic acid and the grape seeds. The results show that, after 3 h of UV-C exposure, approximately 40 % of vanillic acid, 50 % of gallic acid, and 83 % of catechin were removed. Similar degradation rates were observed for vegetal extracts, with the exception of the degradation of catechin (40 %) from grape seeds. In addition, the photo-oxidation of polyphenols in the presence of food constituents such as citric acid, ascorbic acid, sodium chloride, and sodium nitrate was assessed.

Substitution of chloride in [PtCl(bpma)]+ and [PtCl(gly-met-S,N,N)], where bpma is bis(2-pyridylmethyl)amine and gly-met-S,N,N is glycyl-l-methionine, was studied as a function of the entering nucleophile concentration and temperature. Reactions between the platinum(II) complexes and thiourea (TU), iodides (I−), and nitrites(III) (NO2−) were carried out in aqueous solutions using conventional UV-VIS spectrophotometry. Suitable ionic conditions were reached by an addition of 0.1 M NaClO4 and 0.01 M NaCl (to suppress hydrolysis). The second-order rate constants, k 2, for the studied reactions with NO2− varied between 0.036–0.038 M−1 s−1, and for the reactions with TU between 0.095–1.06 M−1 s−1, respectively. The reaction between TU and the [PtCl(bpma)]+ ion is ten times faster than that of the [PtCl(gly-met-S,N,N)] complex. An analysis of the activation parameters, ΔH ≠ and ΔS ≠, for the selected reactions clearly shows their associative nature.

A novel photoactive gemini surfactant was easily synthesised in high yields. The multi-functional molecule can be used as a gemini surfactant, a benzophenone type photoinitiator, and as an ATRP initiator. Poly(methyl methacrylate) (PMMA) and poly(methyl methacrylate)-block-poly(allyl methacrylate) (PMMA-b-PAMA) were prepared using the photoactive gemini surfactant as an ATRP initiator under soap-free miniemulsion polymerisation conditions. Kinetic results of the miniemulsion polymerisation of methyl methacrylate (MMA) indicate that the reaction has controlled/living characteristics. UV curing was performed by irradiation of the linear PMMA-b-PAMA polymer, in which PMMA-b-PAMA containing a benzophenone moiety functioned as a macromolecular photoinitiator.

The singlet and triplet potential energy surfaces for the reaction of HS+ with the simplest primary amine, CH3NH2, were determined at the CCSD(T)/6-311+G(d,p) level using the B3LYP/6-311G(d,p) and QCISD/6-311G(d,p) geometries. All possible reaction channels were explored. The results show that three paths on the singlet potential energy surface and one path on the triplet potential energy surface are competitive. These four feasible paths provide products which are presented in the paper and they are consistent with previous experimental results. On the other hand, the stationary points involved in the most favourable path all lie below those of the reactant and thus the title reaction is expected to be rapid, which is also consistent with the experiment.