Olga Muter

Interrelations of the yeast Candida utilis and Cr(VI): metal reduction and its distribution in the cell and medium

Abstract An effect of chromium(VI) ions on the growth and bioaccumulation properties of growing cells of Candida Utilis was studied. Molasses media for yeast growth containing 20 g glucose l −1 and 50+500 mg Cr(VI) l −1 were used in batch cultivation. Addition of 100 mg Cr(VI) l −1 resulted in a threefold decrease in the cell concentration, as compared with the culture grown without metal. Cr(VI) inhibited culture growth in a concentration-dependent manner, this dependence was not linear. Glucose consumption by growing cells depended on the initial Cr(VI) concentration in the medium and correlated with growth activity. No inhibitory effect of high Cr(VI) concentrations on the activity of some exo-enzymes of C. utilis cells was observed. During C. utilis cultivation, Cr(VI) was partially reduced to an ultimate Cr(III) in all tested ranges of the Cr(VI) concentrations. The specific chromium uptake by cells was detected in biomass that grew in the presence of 100+300 mg Cr(VI) l −1 in a period of 48–96 h. The highest values were achieved after 96 h growth in the presence of 200 and 300 mg Cr(VI) l −1 , and were 7.3 and 7.2 mg Cr g dw l −1 , respectively. Electron microscopic observations showed morphological changes in yeast cells to be more pronounced upon culture growth with 100–300 mg Cr(VI) l −1 than in the cells subjected to higher metal concentrations. The conclusion has been made that the mechanism of the Cr(VI) toxic effect on the growing yeast cells can vary in dependence of the metal concentration.

Biosorption of hexavalent chromium by yeasts

Abstract Different species of yeast exhibit noticeable differences in their ability to sorb Cr(VI). The sorption ability of dehydrated cells is considerably higher than that of intact cells and optimal sorption of chromium takes place at physiological (30°C) or elevated (45°C) temperatures.

Cr(VI) sorption by intact and dehydrated Candida utilis cells in the presence of other metals

This study examined the Cr(VI), Cu(II), Zn(II), Cd(II), Pb(II) sorption by intact and dehydrated Candida utilis cells. The anion [Cr2O7]2− and cation Me2+ sorption kinetics was investigated in both single- and dual-metal situations. Uptake of chromate anions occurred much more slowly singularly than with metal cations. A combination of Pb or Cu and chromate anions gave a synergistic effect for Cr(VI) sorption, but not Cd and Zn, which inhibited Cr(VI) sorption by dehydrated cells. The use of alcian blue to occupy maximum vacant adsorption sites on the cell surface unexpectedly did not influence further adsorption of Me2+. Metal uptake by C. utilis was 7 mg (135 μM) Cr, 23 mg (362 μM) Cu, 39 mg (188 μM) Pb, 19 mg (170 μM) Cd, 28 mg (428 μM) Zn gdw−1. Estimations of the number and area of metal ions occupying the cell surface was made and data obtained indicated that area of sorbed Cr(VI), Cd(II), Cu(II), Pb(II) occupied the single cell did not cover all the surface, whereas Zn(II) covered up to 168%.

The role of nutrients in the biodegradation of 2,4,6-trinitrotoluene in liquid and soil.

The widely used explosive 2,4,6-trinitrotoluene (TNT) has residues that are potentially explosive, toxic, and mutagenic. TNT and other explosives can be degraded by microorganisms; however, biostimulation is needed for process efficiency. To investigate the effectiveness of using biostimulation to degrade TNT, we added varying concentrations of a nutrient amendment consisting of inorganic salts, plant extracts, and molasses to soil and liquid media. For the inoculum we used a consortium of bacteria AM 06 that had exhibited the ability to degrade TNT and which had been previously isolated from explosives-contaminated soils. Phylogenetically, the clones clustered into seven different genera: Klebsiella, Raoultella, Serratia, Stenotrophomonas, Pseudoxanthomonas, Achromobacter and Pseudomonas. The addition of AM 06 consortium to a liquid environment along with 100% nutrient amendment decreased the amount of TNT (and its degradation products) by up to 90% after 14 days incubation. At the total amount of TNT was less than 100 mg/l, the concentration of TNT did not influence the amount of sugar consumed by the bacteria consortium. In soil media, the TNT degradation process was dependent on the concentration of nutrient amendment added. At higher initial concentrations of TNT (500 mg/kg), bioaugmentation (i.e., addition of bacteria inoculum) had a demonstrated effect, especially when nutrient concentrations of 50% and 100% were added to the soil. Findings of this study could further the understanding of the TNT biodegradation processes in water and soil and provide for optimization of the technological conditions for bioremediation.

PHB-based films as matrices for pesticides

Abstract The effects of pesticides incorporated into PHB-based polymeric matrices on the biodegradability of films and antifungal efficiency of immobilised pesticides to Botrytis cinerea was studied. The mass loss of tested PHB-based films for 2 weeks was 40–50% and after 4 weeks 92–96% of the initial mass. The fungicides Ronilan and Sumilex immobilised into the polymeric matrices did not depress the film degradation rate. PHB-based films caused changes in the soil microorganism association. Fungicides immobilised in PHB-based matrices decreased the count of the phytopathogenic fungus B. cinerea.

Effect of plant extract on the degradation of nitroaromatic compounds by soil microorganisms

Remediation of soils contaminated by nitroaromatic compounds and nitramines, i.e. explosives, is known as very important, complicated, and rapidly developing area of biotechnology. A search for optimal growth conditions for soil bacteria is of a great importance in order to isolate various xenobiotic degraders. Bacteria consortium A43 was isolated from soils contaminated with explosives. In the presence of carbohydrate and plant extract, an addition of TNT to the solidified minimal medium stimulated the growth of the tested bacteria, as compared to other bacteria consortium isolated from the same soils. Reducing sugars as carbohydrates, and cabbage leaf extract as a plant extract were used in these experiments. Cultivation of the A43 in liquid medium of the same content showed that addition of cabbage leaf extract alone to medium is much more efficient for TNT degradation by growing biomass as compared to addition of carbohydrate alone.

The effects of woodchip- and straw-derived biochars on the persistence of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) in soils.

Sorption and degradation are the primary processes controlling the efficacy and runoff contamination risk of agrochemicals. This study assessed the influence of two biochars, made from woodchips and straw at a pyrolysis temperature of 725°C and applied to a loamy sand and a sandy soil in the concentration of 5.3 g 100 g(-1) sandy soil and 4.1 g 100 g(-1) loamy sand soil, or 53 t ha(-1) for both soil types, on degradation of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA). Soils were spiked with 50 mg MCPA kg(-1) soil. In the sandy soil, significantly more MCPA remained after 100 days if amended with straw-derived biochar in comparison to wood-derived biochar. Both biochars types significantly increased urease activity (p<0.05) after 37 days in the loamy sand soil, but these differences disappeared after 100 days. A root and shoot elongation test demonstrated that the soils containing straw-derived biochar and spiked with MCPA, showed the highest phytotoxicity. Both biochars were found to retard MCPA degradation in loamy sand and sandy soils. This effect could not be explained only by sorption processes due to comparatively low developed micro/mesoporous structure of both biochars shown by BET surface analysis. However, an enhanced MCPA persistence and soil toxicity in sandy soil amended with straw biochar was observed and further studies are needed to reveal the responsible mechanisms.

Removal of pharmaceuticals from municipal wastewaters at laboratory scale by treatment with activated sludge and biostimulation

Municipal wastewater containing 21 pharmaceutical compounds, as well as activated sludge obtained from the aeration tank of the same wastewater treatment plant were used in lab-scale biodegradation experiments. The concentrations of pharmaceutical compounds were determined by high-performance liquid chromatography coupled to Orbitrap high-resolution mass spectrometry and ranged from 13.2ng/L to 51.8μg/L. Activated sludge was characterized in the terms of phylogenetic and catabolic diversity of microbial community, as well as its morphology. Proteobacteria (24.0%) represented the most abundant phylum, followed by Bacteroidetes (19.8%) and Firmicutes (13.2%). Bioaugmentation of wastewater with activated sludge stimulated the biodegradation process for 14 compounds. The concentration of carbamazepine in non-amended and bioaugmented WW decreased during the first 17h up to 30% and 70%, respectively. Diclofenac and ibuprofen demonstrated comparatively slow removal. The stimulating effect of the added nutrients was observed for the degradation of almost all pharmaceuticals detected in WW. The most pronounced effect of nutrients was found for erythromycin. The results were compared with those obtained for the full-scale WW treatment process.

Cr(VI) sorption by intact and dehydrated Candida utilis cells: differences in mechanisms

The Cr(VI) sorption kinetics by intact and dehydrated Candida utilis cells were studied. Yeast dehydration led to enhanced Cr(VI) sorption activity by cells during the first 15–20 min of rehydration. In experiments with K2Cr2O7 as a chromium source, [Cr2O7]2− was converted into [CrO4]2− during incubation with dehydrated biomass. An effect of the considerably enhanced Cr(VI) sorption activity by dehydrated cells in the buffered media at pH≈8.0 can serve as another confirmation of the different sorption mechanisms of intact and dehydrated C.utilis cells. This effect was not revealed in water solution at pH 8.0. This phenomenon will be studied in further investigations.

Microbial community changes in TNT spiked soil bioremediation trial using biostimulation, phytoremediation and bioaugmentation

AbstractTrinitrotoluene (TNT), a commonly used explosive for military and industrial applications, can cause serious environmental pollution. 28-day laboratory pot experiment was carried out applying bioaugmentation using laboratory selected bacterial strains as inoculum, biostimulation with molasses and cabbage leaf extract, and phytoremediation using rye and blue fenugreek to study the effect of these treatments on TNT removal and changes in soil microbial community responsible for contaminant degradation. Chemical analyses revealed significant decreases in TNT concentrations, including reduction of some of the TNT to its amino derivates during the 28-day tests. The combination of bioaugmentation-biostimulation approach coupled with rye cultivation had the most profound effect on TNT degradation. Although plants enhanced the total microbial community abundance, blue fenugreek cultivation did not significantly affect the TNT degradation rate. The results from molecular analyses suggested the survival and...