Zoltán Illés

Effect of non-ionic tensides on the growth of some soil bacteria

SummaryThe effect of some nonylphenyl-ethylene oxide polymers on the growth of Bacillus megaterium, B. cereus var. mycoides, B. polymyxa, B. subtilis, Pseudomonas fluorescence and Azotobacter chroococcum was investigated in the concentration range 20–800 ppm with the agar diffusion method. The zones of inhibition, restricted growth and eventual stimulation were determined with a Shimadzu C-930 dual wavelength TLC scanner. The data matrix was evaluated by principal component analysis. A. chroococcum was insensitive to each tenside at each concentration. The growth of the other microorganisms was inhibited by the tensides. With B. megaterium and B. cereus var. mycoides stimulation was also observed. The effect of the non-ionic tensides decreased with increasing length of the hydrophilic ethylene oxide chain. This phenomenon can be explained by the assumption that the activity of tensides depends on their membrane-damaging effect. The bulky nonylphenyl group inserts between the apolar fatty acid chains disorganizing the membrane structure. The longer hydrophilic ethylene oxide chain modifies the distribution of tenside between the apolar and polar regions of the membrane, preferring the aqueous phase. This results in the decrease or loss of biological activity.

Liquid chromatographic and electrophoretic characterisation of extracellular β-glucosidase of Pleurotus ostreatus grown in organic waste

The production of beta-glucosidase by the ligninolytic fungus Pleurotus ostreatus has been studied in different culture media containing agro-industrial wastes. The enzyme is purified by anion-exchange chromatography, the molecular mass and isoelectric point of purified beta-glucosidase are measured by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and isoelectric focusing and the stability and kinetic parameters of the enzyme assessed by spectrophotometry. It has been established that the retention time, molecular mass and isoelectric point of the enzyme depend on the composition of the culture media while the activity and stability of beta-glucosidases of different origin were very similar. The combined chromatographic and electrophoretic methods have proved to be suitable techniques for the purification and characterisation of the beta-glucosidases produced by the ligninolytic fungus Pleurotus ostreatus in different culture media.

Comparison of two principal component analysis methods to evaluate reversed-phase retention data

The retention of twelve 2-nitro-4-cyanophenyl esters showing marked herbicidal activity was determined in 23 reversed-phase thin-layer chromatographic systems. The retention data set was evaluated by principal component analysis (PCA). To assess the effect of the information loss caused by normalization, PCA was separately carried out on the covariance (method A) and on the correlation matrix (method B). The ratio of the variances explained was very similar for both methods, however, the PC loadings and the coordinates of the two-dimensional nonlinear maps showed poor correlation. The distribution of the 2-nitro-4-cyanophenyl esters and that of chromatographic systems showed differences on the two-dimensional nonlinear maps of PC loadings and PC variables, however, the general trend was similar independently of the application of method A or B. The findings indicate that the application of the correlation matrix as basis for the PCA calculations may lead to slightly distorted results that strongly advocates the use of covariance matrix in PCA.

Effect of the Composition of Culture Media on the Laccase Production of Lentinus edodes Strains

The effect of charge, ion radii and concentration of cations and fermentation time on the laccase production of four Lentinus edodes strains was determined using 28 different fermentation media and 60 days of fermentation time. Samples were taken every 10 days and the laccase activity was determined by visible spectrophotometry. Principal component analysis (PCA) was used for the assessment of similarities and dissimilarities between the laccase activities of the samples. As PCA is not suitable for the separation of the strength (potency) and selectivity of the effect of various factors (composition of cultures, fermentation time, Lentinus edodes strains) on the laccase production, they were separated by the spectral mapping technique (SPM). The dimensionality of the matrices of PC loadings and variables and the selectivity maps were reduced to two by the non-linear mapping technique. The results of PCA and SPM were compared by calculating linear relationships among the potency values and the corresponding coordinates of PCA and SPM maps. It was established that neither the type of the cations nor their concentration in the fermentation media had a significant effect on the laccase production. It was found that the type of the Lentinus edodes strains and the fermentation time exerts a considerable effect both on the strength and on the selectivity of the laccase production. It was further proven that the results of PCA and SPM were considerably different. Therefore, their simultaneous application in future quantitative structure activity relationship (QSAR) studies is highly recommended.

Retention Behavior of Some Thiophosphorylglycinamide Fungicides in Adsorption and Reversed‐Phase Thin‐Layer Chromatography

Abstract The free energy of adsorption, the surface area of adsorption on silica and alumina surfaces, and the molecular lipophilicity of 37 thiophosphorylglycinamide (TPGA) derivatives was determined by thin layer chromatography using silica and alumina supports and silica support impregnated with paraffin oil. The relationships between the physicochemical characteristics of analytes were elucidated by stepwise regression analysis. It was found that the physicochemical parameters showed high variety between the derivatives, and they depended markedly on the silica and alumina surfaces. In the majority of cases, no linear correlation was found between the parameters. The free energy of adsorption and the surface area of adsorption on the silica surface showed highly significant correlation, indicating that the energy of adsorption per unit surface is similar for each of the TPGA derivatives and the molecular substructures involved in the adsorption are probably chemically similar.

Interaction of Hydroxypropyl‐β‐Cyclodextrin with Peptides, Studied by Reversed‐Phase Thin‐Layer Chromatography

Abstract The effect of various concentrations of hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) on the reversed‐phase thin‐layer chromatographic mobility of some low molecular mass peptides was measured in distilled water and in 0.05 M of LiCl, NaCl, KCl, RbCl, and CsCl solutions, and the relative strength of HP‐β‐CD–peptide interaction has been calculated from the dependence of retention on the concentration of HP‐β‐CD in the mobile phase. Lipophilicity of the peptides decreased regularly with increasing concentration of HP‐β‐CD in the mobile phase, proving the interaction (probably the formation of inclusion complexes) between peptides and HP‐β‐CD. Principal component analysis indicated that each salt influenced the interaction differently. Peptides formed clusters on the two‐dimensional nonlinear map according to the character of the amino acid monomer and not according to the number of amino acid units, suggesting that only one terminal amino acid is included in the cavity of HP‐β‐CD.

TLC Study of the Binding of Nonionic Surfactants to the Corn Protein Zein

Abstract The binding of 18 nonionic surfactants with various lengths of apolar ethylene oxide chains to the corn protein zein was studied by thin‐layer chromatography (TLC) carried out on alumina layers covered with zein, and the effect of methanol, monovalent cations, and pH on the strength and selectivity of interaction was elucidated by using the spectral mapping technique and stepwise regression analysis. The binding of surfactants to zein has been demonstrated. It has been established that the number of hydrophilic ethylene oxide units in the surfactant molecule exerts the highest influence on the strength of interaction, and that the role of methanol and salt concentration is of secondary importance. The character of the cation and pH influenced both the strength and selectivity of the surfactant–zein interaction.

Interaction of Pesticides with a β-Cyclodextrin Derivative Studied by Reversed-phase Thin-layer Chromatography and Principal Component Analysis

The interaction of 18 pesticides with a water-soluble β-cyclodextrin polymer (BCDP) was studied by reversed-phase thin-layer chromatography and principal component analysis (PCA) was employed for the elucidation of the relationship between the relative strength of interaction and the calculated surface parameters of the guest molecules. Except for penconazole the lipophilicity of the pesticides decrease in the presence of BCDP. PCA indicated that apolar surface parameters are highly positively correlated with the strength of interaction. The data indicate that the agrochemical characteristics (adsorption, leakage, decomposition, etc) of complexed pesticide molecules can be different from those of uncomplexed onesresulting in modified efficacy.

Industrial chemical regulation in the European Union and the United States: a comparison of REACH and the amended TSCA

Abstract In June 2016, after decades of debate, the U.S. Congress enacted a major revision to the Toxic Substances Control Act (TSCA) of 1976, the U.S. regulatory law applicable to industrial chemicals. It has been theorized that Europe may seek to export its stricter environmental standards under REACH to the United States. Thus, it is interesting to examine whether the environmental, health, and safety practices – including the values – found in REACH impacted the TSCA reform debate in the U.S. We chose to focus the comparison on the following issues that were central features of REACH: responsibility to develop safety data, priorities for safety assessments, definition of the safety standard, restrictions on chemical use, and preemption of regulatory activity by lower levels of government. There are three major findings. First, the U.S. did not implement the EU’s solution of putting the burden of data generation, risk assessment, and risk management on the industry. Second, REACH is more precautionary in its design than the amended TSCA. Third, the new U.S. law is generally less strict than REACH in their requirements on industry, though it is also less preemptive of lower levels of government than REACH is. Moreover, the U.S. retains a common law approach to chemical-induced injury that is more punitive of industrial errors than is European Union law. The EU’s attempt to export REACH regulation failed in the case of U.S.A., as the U.S. Congress did not reform TSCA based on the REACH model. We conclude that, although the problems identified prior to the enactment of REACH were similar to those identified in the U.S., REACH’s key principles and elements were not adopted in the U.S.