Effect of hexavalent chromium on the biodegradation of tetrabromobisphenol A (TBBPA) by Pycnoporus sanguineus

Biodegradation of phenolic pollutants and bioaugmentation strategies: A review of current knowledge and future perspectives

The widespread use of phenolic compounds renders their occurrence in various environmental matrices, posing ecological risks especially the endocrine disruption effects. Biodegradation-based techniques are efficient and cost-effective in degrading phenolic pollutants with less production of secondary pollution. This review focuses on phenol, 4-nonylphenol, 4-nitrophenol, bisphenol A and tetrabromobisphenol A as the representatives, and summarizes the current knowledge and future perspectives of their biodegradation and the enhancement strategy of bioaugmentation. Biodegradation and isolation of degrading microorganisms were mainly investigated under oxic conditions, where phenolic pollutants are typically hydroxylated to 4-hydroxybenzoate or hydroquinone prior to ring opening. Bioaugmentation efficiencies of phenolic pollutants significantly vary under different application conditions (e.g., increased degradation by 10-95% in soil and sediment). To optimize degradation of phenolic pollutants in different matrices, the factors that influence biodegradation capacity of microorganisms and performance of bioaugmentation are discussed. The use of immobilization strategy, indigenous degrading bacteria, and highly competent exogenous bacteria are proposed to facilitate the bioaugmentation process. Further studies are suggested to illustrate 1) biodegradation of phenolic pollutants under anoxic conditions, 2) application of microbial consortia with synergistic effects for phenolic pollutant degradation, and 3) assessment on the uncertain ecological risks associated with bioaugmentation, resulting from changes in degradation pathway of phenolic pollutants and alterations in structure and function of indigenous microbial community.

Biodegradation of Trichloroethylene by Trametes versicolor and its Physiological Response to Contaminant Stress

Trichloroethylene (TCE) poses a potentially toxic threat to humans and the environment and widely exists in contaminated sites. White rot fungi effectively degrade refractory pollutants, while a few research studies use white rot fungi to degrade TCE. In this study, we investigated TCE biodegradation by white rot fungi and the potential influencing factors in the environment and attempted to research the effect of TCE on the physiological characteristics of white rot fungi. White rot fungi (Trametes versicolor, Pseudotrametes gibbosa, Pycnoporus sanguines and Pleurotus ostreatus) were added to the liquid medium for shock culture. The results revealed that T. versicolor exhibited the most pronounced efficacy in removing TCE, with a degradation rate of 81.10% within a 7 d period. TCE induces and is degraded by cytochrome P450 enzymes. High pH and Cr(VI) adversely affected the effectiveness of the biodegradation of TCE, but the salinity range of 0-1% had less effect on biodegradation. Overall, the effectiveness of degradation of TCE by T. versicolor has been demonstrated, and it provides a reference for the application prospects of white rot fungi in TCE-contaminated soils.

Integration of transcriptomic and proteomic reveals the toxicological molecular mechanisms of decabromodiphenyl ethane (DBDPE) on Pleurotus ostreatus

Decabromodiphenyl ethane (DBDPE), as one of the most widely used new brominated flame retardants (NBFRs), can pose a potential threat to human health and the environment. An integrated transcriptome and proteome was performed for investigating the toxicological molecular mechanisms of Pleurotus ostreatus (P. ostreatus) during the biodegradation of DBDPE at the concentrations of 5 and 20 mg/L. A total of 1193/1018 and 92/126 differentially expressed genes/proteins (DEGs/DEPs) were found, respectively, with DBDPE exposure at 5 and 20 mg/L. These DEGs and DEPs were mainly involved in the cellular process as well as metabolic process. DEPs for oxidation-reduction process and hydrolase activity were up-regulated, and those for membrane, lipid metabolic process and transmembrane transport were down-regulated. The DEGs and DEPs related to some key enzymes were down-regulated, such as NADH dehydrogenase/oxidoreductase, succinate dehydrogenase, cytochrome C1 protein, cytochrome-c oxidase/reductase and ATP synthase, which indicated that DBDPE affected the oxidative phosphorylation as well as tricarboxylic acid (TCA) cycle. Cytochrome P450 enzymes (CYPs) might be involved in DBDPE degradation through hydroxylation and oxidation. Some stress proteins were induced to resist DBDPE toxicity, including major facilitator superfamily (MFS) transporter, superoxide dismutase (SOD), molecular chaperones, heat shock proteins (HSP20, HSP26, HSP42), 60S ribosomal protein and histone H4. The findings help revealing the toxicological molecular mechanisms of DBDPE on P. ostreatus, aiming to improve the removal of DBDPE.

Hydrogen sulfide and calcium effects on cadmium removal and resistance in the white-rot fungus Phanerochaete chrysosporium

Hydrogen sulfide (H₂S), an emerging gas transmitter, has been shown to be involved in multiple intracellular physiological and biochemical processes. In this study, the effects of hydrogen sulfide coupled with calcium on cadmium removal and resistance in Phanerochaete chrysosporium were examined. The results revealed that H₂S enhanced the uptake of calcium by P. chrysosporium to resist cadmium stress. The removal and accumulation of cadmium by the mycelium was reduced by H₂S and Ca²⁺ pretreatment. Moreover, oxidative damage and membrane integrity were alleviated by H₂S and Ca²⁺. Corresponding antioxidative enzyme activities and glutathione were also found to positively respond to H₂S and Ca²⁺, which played an important role in the resistance to cadmium-induced oxidative stress. The effects of hydroxylamine (HA; a hydrogen sulfide inhibitor) and ethylene glycol-bis-(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA; a calcium chelator) toward H₂S and Ca²⁺ and their cross-interactions confirmed the positive roles and the potential crosstalk of H₂S and Ca²⁺ in cadmium stress resistance. These findings imply that the protective effects of H₂S in P. chrysosporium under cadmium stress may occur through a reduction in the accumulation of cadmium and promotion of the antioxidant system, and the H₂S-regulated pathway may be associated with the intracellular calcium signaling system.Key points• Altered monoterpenoid tolerance mainly related to altered activity of efflux pumps.• Increased tolerance to geranic acid surprisingly caused by decreased export activity.• Reduction of export activity can be beneficial for biotechnological conversions.

Single and combined effects of divalent copper and hexavalent chromium on the performance, microbial community and enzymatic activity of sequencing batch reactor

Divalent copper (Cu²⁺) and hexavalent chromium (Cr⁶⁺) are often encountered in industrial wastewater and municipal wastewater, the effect of combined Cu²⁺ and Cr⁶⁺ on biological wastewater treatment systems has cause wide concern. In the present research, the performance, microbial community and enzymatic activity of sequencing batch reactors (SBRs) were compared under the single and combined Cu²⁺ at 20 mg/L and Cr⁶⁺ at 10 mg/L. The chemical oxygen demand (COD) and ammonia nitrogen (NH₄⁺-N) removal efficiencies under the combined Cu²⁺ and Cr⁶⁺ were less than those under the single Cu²⁺ and Cr⁶⁺. The combined Cu²⁺ and Cr⁶⁺ displayed more inhibition effects on the oxygen uptake rate, nitrification rate and denitrification rate of activated sludge than the single Cu²⁺ and Cr⁶⁺. The inhibitory effects of the combined Cu²⁺ and Cr⁶⁺ on the activities of dehydrogenase, ammonia monooxygenase, nitrite oxidoreductase, nitrite reductase and nitrate reductase showed significant increases by comparison with the single Cr⁶⁺. However, the combined Cu²⁺ and Cr⁶⁺ had a little more inhibitory effects on the enzymatic activities than the single Cu²⁺. The microbial richness and diversity displayed some obvious changes under the single and combined Cu²⁺ and Cr⁶⁺ by comparison the absence of Cu²⁺ and Cr⁶⁺. The relative abundances of nitrifying genera (e.g. Nitrosomonas and Nitrospira) under the combined Cu²⁺ and Cr⁶⁺ was less than those under the single Cu²⁺ and Cr⁶⁺. These findings will be helpful to better understand the combined effects of multiple heavy metals on biological wastewater treatment systems.