Degradation Potential of the Nonylphenol Monooxygenase of Sphingomonas sp. NP5 for Bisphenols and Their Structural Analogs

Chlorination of bisphenols in water: Understanding the kinetics and formation mechanism of 2-butene-1,4-dial and analogues

While it is widely accepted that 2-butene-1,4-dial (BDA) is a toxic metabolite with genotoxic and carcinogenic properties, little is known about BDA and its analogues (BDAs) formation during water disinfection. In this study, the effects of different chlorination conditions on the formation of BDAs from bisphenol and its analogues (BPs analogues) were evaluated. A transformation pathway for the formation of BDAs upon chlorination of BPs analogues is proposed. The time profile of the transformation of BPs analogues into BDAs reveals that the generation of dichlorohydroquinone, dichloro-hydroxybenzenesulfonic acid and 2,4,6-trichlorophenol, are significantly associated with the formation of BDAs in the disinfected water. Owing to the different bridging groups contributing to the electrophilicity of BPs analogues in varying degrees, the stronger the electrophilicity of BPs analogues the more BDAs are formed. In addition, the type of BDAs produced is also affected. Four types of BDAs were detected in this study, one of which was newly identified. This study confirms that BPs analogues are an important source of BDAs and provides more insights into the formation of BDAs during chlorination. Greater attention should be given to the formation of BDAs in chlorinated water and their potential threat to humans and the ecosystem.

Revealing the driving synergistic degradation mechanism of Rhodococcus sp. B2 on the bioremediation of pretilachlor-contaminated soil

The pretilachlor has been widely used worldwide and has contaminated the environment for many years. The environmental fate of pretilachlor and its residues removal from the contaminated environment have attracted great concern. Reportedly, pretilachlor could partly be transformed to HECDEPA by Rhodococcus sp. B2. However, the effects of pretilachlor on soil bacterial communities and its complete metabolic pathway remain unknown. Herein, we investigated the mechanism of driving synergistic degradation of pretilachlor by strain B2 in the soil. The results revealed that pretilachlor showed a negative effect on bacterial communities and caused significant variations in the community structure. Strain B2 showed the ability to remediate the pretilachlor-contaminated soils and network analysis revealed that it may drive the enrichment of potential pretilachlor-degrading bacteria from the soil. The soil pretilachlor degradation may be facilitated by the members of the keystone families Comamonadaceae, Caulobacteraceae, Rhodospirillaceae, Chitinophagaceae, and Sphingomonadaceae. Meanwhile, Sphingomonas sp. M6, a member of the Sphingomonadaceae family, has been isolated from the strain B2 inoculation sample soil. The co-culture, comprising strain M6 and B2, could synergistic degrade pretilachlor within 30 h, which is the highest degradation rate. Strain M6 could completely degrade the HECDEPA via CDEPA and DEA. In the soil, a comparable pretilachlor degradation pathway may exist. This study suggested that strain B2 had the potential to drive the remediation of pretilachlor-contaminated soils.

Aerobic starvation treatment of activated sludge enhances the degradation efficiency of refractory organic compounds

Many refractory organic compounds (ROCs) in wastewater are toxic to human and aquatic organisms. Here, we reported an aerobic starvation approach to improve the degradation efficiencies of ROCs in activated sludge systems. The highest degradation rates of bisphenol AF (BPAF) (11.4 mg/g VSS · h) and gabapentin (GBP) (8.9 mg/g VSS · h) were achieved on the second day of the starvation process. While, the degradation rate of bisphenol A (BPA) on the 43rd day reached the maximum value of 0.8 mg/g VSS ·h, which was significantly higher than that of the seeding sludge (0.01 mg/g VSS · h). To investigate the mechanisms of this finding, we applied magnetic-nanoparticle mediated isolation, 16S rRNA gene sequencing, metagenomic sequencing and metatranscriptomic sequencing to analyze the microbial community structures and functions during the starvation process. The results showed that the increase of the BPA degradation ability was caused by the increase of the relative abundance of BPA degrading bacteria (Sphingomonas, Achromobacter, etc.), while, the enhancement of BPAF and GBP degradation was attributed to the increase of the expression of ROC degrading genes. Overall, these results improve our understanding of the microbial ecology of starved activated sludge and provide useful information for the future development of ROC removal technologies.

New insights into thiamphenicol biodegradation mechanism by Sphingomonas sp. CL5.1 deciphered through metabolic and proteomic analysis

Biological treatment is an efficient and economical process to remove thiamphenicol (TAP) residues from the environment. The discovery of TAP-degrading bacteria and the decryption of its biodegradation mechanism will be beneficial to enhance the biological removal of TAP. In this study, Sphingomonas sp. CL5.1 was found to be capable of catabolizing TAP as the sole carbon, nitrogen, and energy source. This strain could degrade 93.9% of 25 mg/L TAP in 36 h, and remove about 11.9% of the total organic carbon of TAP. A novel metabolism pathway of TAP was constructed, and the enzymes involved in TAP metabolism in strain CL5.1 were predicted via proteomic and metabolic analysis. TAP was proposed to be transformed to O-TAP via oxidation of C₃-OH and DD-TAP via dehydration of C₃-OH and dehydrogenation of C₁-OH. A novel glucose-methanol-choline (GMC) family oxidoreductase CapO was predicted to be involved in the oxidation of C₃-OH. O-TAP was supposed to be further cleaved into DCA, glycine, and PMB. Glycine might be a pivotal direct nitrogen source for strain CL5.1, and it could be involved in nitrogen metabolism through the glycine cleavage system or directly participate in the biosynthetic processes.

Transcriptomic analysis reveals ligninolytic enzymes of white-rot fungus Phanerochaete sordida YK-624 participating in bisphenol F biodegradation under ligninolytic conditions

Bisphenol F (BPF) is widely used in the plastic manufacturing industry as a replacement for bisphenol A (BPA) because BPF and BPA have similar structures and comparable properties. However, BPF is ubiquitously present in the environment and has higher toxicity to humans. This study is the first to report BPF degradation using the white-rot fungus Phanerochaete sordida YK-624 under ligninolytic conditions (pH=4.5, 30 °C). P. sordida YK-624 almost completely degraded BPF within 4 days. Moreover, functional genes involved in BPF degradation were detected by RNA-Seq. Metabolic processes and peroxidases were enriched by GO analysis, and the metabolic pathway was enriched according to the KEGG pathway analysis. These results suggested that P. sordida YK-624 could secrete higher levels of ligninolytic enzymes lignin peroxidase (LiP) and manganese peroxidase (MnP) for BPF degradation. The results indicated that LiPs and MnPs are important for BPF degradation and cytochrome P450s play a small role. Furthermore, reliability of the RNA-Seq results was validated by qRT-PCR.

Dietary jellyfish affect digestive enzyme activities and gut microbiota of Pampus argenteus

For many years, jellyfish were described as 'dead ends' in marine food webs, due to their high-water content and low nutritional value. However, it has been confirmed that silver pomfret (Pampus argenteus) has a particular preference for preying on jellyfish. In this study, we determined the effect of consuming jellyfish on the intestinal microbes of silver pomfret. Analysis of bacterial 16S rRNA gene amplicons showed that jellyfish had a dramatic impact on the composition of the gut microbiota. The content of Proteobacteria was reduced from 99% to 51%, while Firmicutes, Bacteroidetes and Actinobacteria increased, accounting for 35%, 9% and 2% of the total flora, respectively. At the genus level, the content of Photobacterium decreased sharply to <1% of the total flora. By contrast, Lactobacillus, Burkholderia and Sphingomonas increased to 12%, 9% and 7% of the total flora, respectively. After feeding jellyfish, the functions of intestinal microbes and the activity of digestive enzymes also changed, resulting in better digestion and absorption of jellyfish. The results provide insights into the specific bacterial taxa within the silver pomfret intestinal microbiome that are impacted by jellyfish. Silver pomfret can better digest and absorb jellyfish by adjusting the intestinal microbial composition. The findings provide a theoretical basis for the digestive mechanism by which silver pomfret consume jellyfish.

Occurrence, potential ecological risks, and degradation of endocrine disrupter, nonylphenol, from the aqueous environment

Nonylphenol (NP) is considered a potential endocrine-disrupting chemical affecting humans and the environment. Due to widespread occurrence in the aquatic environment and neuro-, immuno, reproductive, and estrogenic effects, nonylphenol calls for considerable attention from the scientific community, researchers, government officials, and the public. It can persist in the environment, especially soil, for a long duration because of its high hydrophobic nature. Nonylphenol is incorporated into the water matrices via agricultural run-off, wastewater effluents, agricultural sources, and groundwater leakage from the soil. In this regard, assessment of the source, fate, toxic effect, and removal of nonylphenol seems a high-priority concern. Remediation of nonylphenol is possible through physicochemical and microbial methods. Microbial methods are widely used due to ecofriendly in nature. The microbial strains of the genera, Sphingomonas, Sphingobium, Pseudomonas, Pseudoxanthomonas, Thauera, Novosphingonium, Bacillus, Stenotrophomonas, Clostridium, Arthrobacter, Acidovorax, Maricurvus, Rhizobium, Corynebacterium, Rhodococcus, Burkholderia, Acinetobacter, Aspergillus, Pleurotus, Trametes, Clavariopsis, Candida, Phanerochaete, Bjerkandera, Mucor, Fusarium and Metarhizium have been reported for their potential role in the degradation of NP via its metabolic pathway. This study outlines the recent information on the occurrence, origin, and potential ecological and human-related risks of nonylphenol. The current development in the removal of nonylphenol from the environment using different methods is discussed. Despite the significant importance of nonylphenol and its effects on the environment, the number of studies in this area is limited. This review gives an in-depth understanding of NP occurrence, fate, toxicity, and remediation from the environments.

Kinetics and biotransformation products of bisphenol F and S during aerobic degradation with activated sludge

Bisphenol F (BPF) and bisphenol S (BPS) are becoming widespread in the environment despite the lack of information regarding their fate during wastewater treatment and in the environment. This study assessed the biodegradation kinetics of BPF and BPS during biological wastewater treatment with activated sludge using GC-MS/MS, and the identification of biotransformation products (BTPs) using LC-QTOF-MS. The results showed that BPF and BPS degrade readily and unlikely accumulate in biosolids or wastewater effluent (c_i = 0.1 mg L^-1, half-lives <4.3 days). The first-order kinetic model revealed that BPF (k_t = 0.20-0.38) degraded faster than BPS (k_t = 0.04-0.16) and that degradation rate decreases with an increasing initial concentration of BPS (half-lives 17.3 days). The absence of any additional organic carbon source significantly slowed down degradation, in particular, that of BPS (lag phase on day 18 instead of day 7). The machine-learning algorithm adopted as part of the non-targeted workflow identified three known BTPs and one novel BTP of BPF, and one known and ten new BTPs of BPS. The data from this study support possible new biodegradation pathways, namely sulphation, methylation, cleavage and the coupling of smaller bisphenol moieties.

Microbial capability for the degradation of chemical additives present in petroleum-based plastic products: A review on current status and perspectives

Plastic additives are present as pollutants in the environment because they are released from plastics and have been reported to be toxic to mammals. Due to this toxicity, it is crucial to develop ecofriendly tools to decontaminate the environment. Microorganisms are a promising alternative for efficient and effective plastic additive removal. This review describes the current knowledge and significant advances in the microbial degradation of plastic additives (i.e. plasticizers, flame retardants, stabilizers and antioxidants) and biotechnological research strategies that are being used to accelerate the biodegradation process of these additives. It is expected that further research supported by advances in genomics, proteomics, gene expression, enzyme immobilization, protein design, and nanotechnology can substantially increase our knowledge to enhance the enzymatic degradation efficiency, which will accelerate plastic additive degradation and establish successful and cost-effective bioremediation processes. Investigations should also address the identification of the enzymes involved in the degradation process and their catalytic mechanisms to achieve full metabolization of organopollutants (i.e. plastic additives) while avoiding harmful plastic additive biodegradation products. Microorganisms and their enzymes undoubtedly represent a potential resource for developing promising environmental biotechnologies, as they have the best systems for pollutant degradation, and their actions are essential for decontaminating the environment.