A key esterase required for the mineralization of quizalofop-p-ethyl by a natural consortium of Rhodococcus sp. JT-3 and Brevundimonas sp. JT-9

Cloning and Expression of the Isoprocarb Hydrolase Gene cehA from the Newly Isolated Isoprocarb-Degrading Strain Sphingobium sp. R-7

To remove the isoprocarb residues from the environment, a bacterial strain that was capable of degrading isoprocarb was isolated from agricultural soils where isoprocarb has been applied for a long period, and named R-7. On the basis of its cellular morphology and phenotypic features and 16S rRNA phylogenetic analysis, strain R-7 was preliminarily identified as Sphingobium sp. This strain could grow on isoprocarb as a sole carbon source and degrade 98.3% of 0.5 mM of isoprocarb within 16 h in batch liquid culture. The metabolite produced was identified as 2-isopropylphenol by high-performance liquid chromatography and tandem mass spectrometry (HPLC-MS/MS) analysis. Strain R-7 hydrolysed the ester bond of isoprocarb to generate 2-isopropylphenol, but this metabolite was not further degraded. Upon the genome comparison, the isoprocarb hydrolase gene cehA was cloned from strain R-7 and expressed in Escherichia coli BL21. The purified CehAR-7 displayed maximal enzymatic activity at 40 °C and pH 7.0. The apparent Km and kcat values of CehAR-7 for isoprocarb were 169.12 ± 7.74 µmol L-1 and 347 ± 17.73 min-1, respectively. CehAR-7 could hydrolyse carbaryl and isoprocarb efficiently, although its ability to hydrolyse carbofuran, oxamyl and methomyl was poor. In conclusion, this study provided an efficient isoprocarb-degrading microorganism, and identified the isoprocarb hydrolase CehA from strain R-7, which has potential applications for microbial remediation of isoprocarb-polluted environments.

QpmH esterase from cotton rhizosphere bacteria: A novel approach for degrading quizalofop-p-ethyl herbicide

Within the rhizosphere, a rich population of biocontrol bacteria serves as a valuable resource for the biodegradation of environmental herbicides. This study aimed to evaluate rhizospheric microorganisms for their potential to degrade Quizalofop-p-ethyl, a widely used herbicide to control annual and perennial weeds in a variety of crops. A bacterial strain, MJ-8, isolated from cotton rhizosphere soil, demonstrated significant degradation activity. Based on morphological characteristics and 16S rRNA sequencing, the strain was identified as Priestia megaterium. Strain MJ-8 achieved a degradation rate of 90.65 % for Quizalofop-p-ethyl. Genomic analysis and amino acid sequence alignment revealed a key gene, designated QpmH, encoding a 30 kDa protein with strong biodegradation activity. Heterologous expression of the QpmH gene confirmed its role in Quizalofop-p-ethyl degradation. Molecular docking studies and structural modeling further elucidated the enzymatic mechanisms, supported by the analysis of their degradation products. Additionally, when QpmH gene was introduced into rice plants through Agrobacterium-mediated transformation, the resultant transformant conferred resistance to Quizalofop-p-ethyl at the recommended application dose. These findings highlight Priestia megaterium strain MJ-8 as a promising biological agent for sustainable herbicide management and position the QpmH gene as a potential new target for developing herbicide-resistant crops.

Efficient Biodegradation of Multiple Aryloxyphenoxypropionate Herbicides by Corynebacterium sp. Z-1 and the Proposed Degradation Mechanism

Esterases are crucial for aryloxyphenoxypropionate herbicide (AOPP) biodegradation. However, the underlying molecular mechanisms of AOPP biodegradation by esterases are poorly understood. In the current work, Corynebacterium sp. Z-1 was isolated and found to degrade multiple AOPPs, including quizalofop-p-ethyl (QPE), haloxyfop-p-methyl (HPM), fenoxaprop-p-ethyl (FPE), cyhalofop-butyl (CYB), and clodinafop-propargyl (CFP). A novel esterase, QfeH, which catalyzes the cleavage of ester bonds in AOPPs to form AOPP acids, was identified from strain Z-1. The catalytic activities of QfeH toward AOPPs decreased in the following order: CFP > FPE > CYB > QPE > HPM. Molecular docking, computational analyses, and site-directed mutagenesis indicated the catalytic mechanisms of QfeH-mediated degradation of different AOPPs. Notably, the key residue S159 is essential for the activity of QfeH. Moreover, V222Y, T227M, T227A, A271R, and M275K mutants, exhibiting 2.9-5.0 times greater activity than QfeH, were constructed. This study facilitates the mechanistic understanding of AOPPs bioremediation by esterases.

Characterization of two novel hydrolases from Sphingopyxis sp. DBS4 for enantioselective degradation of chiral herbicide diclofop-methyl

Diclofop-methyl, an aryloxyphenoxypropionate (AOPP) herbicide, is a chiral compound with two enantiomers. Microbial detoxification and degradation of various enantiomers is garnering immense research attention. However, enantioselective catabolism of diclofop-methyl has been rarely explored, especially at the molecular level. This study cloned two novel hydrolase genes (dcmA and dcmH) in Sphingopyxis sp. DBS4, and characterized them for diclofop-methyl degradation. DcmA, a member of the amidase superfamily, exhibits 26.1-45.9% identity with functional amidases. Conversely, DcmH corresponded to the DUF3089 domain-containing protein family (a family with unknown function), sharing no significant similarity with other biochemically characterized proteins. DcmA exhibited a broad spectrum of substrates, with preferential hydrolyzation of (R)-(+)-diclofop-methyl, (R)-(+)-quizalofop-ethyl, and (R)-(+)-haloxyfop-methyl. DcmH also preferred (R)-(+)-quizalofop-ethyl and (R)-(+)-haloxyfop-methyl degradation while displaying no apparent enantioselective activity towards diclofop-methyl. Using site-directed mutagenesis and molecular docking, it was determined that Ser175 was the fundamental residue influencing DcmA's activity against the two enantiomers of diclofop-methyl. For the degradation of AOPP herbicides, DcmA is an enantioselective amidase that has never been reported in research. This study provided novel hydrolyzing enzyme resources for the remediation of diclofop-methyl in the environment and deepened the understanding of enantioselective degradation of chiral AOPP herbicides mediated by microbes.

A novel cold-adapted pyrethroid-degrading esterase from Bacillus subtilis J6 and its application for pyrethroid-residual alleviation in food matrix

Prolonged and widespread use of pyrethroid pesticides a significant concern for human health. The initial step in pyrethroid bioremediation involves the hydrolysis of ester-bond. In the present study, the esterase genes est10 and est13, derived from Bacillus subtilis, were successfully cloned and expressed in Escherichia coli. Recombinant Est10 and Est13 were classified within esterase families VII and XIII, respectively, both of which exhibited conserved G-X-G-X-G motifs. These enzymes demonstrated the capability to degrade pyrethroids, with Est13 exhibiting superior efficiency, and thus was selected for further investigation. The degradation products of β-cypermethrin by Est13 were identified as 3-phenoxybenzoic acid, 3-phenoxybenzaldehyde, and 3-(2,2-Dichloroethenyl)- 2,2-dimethyl-cyclopropanecarboxylate, with key catalytic triads comprising Ser93, Asp192, and His222. Notably, Est13 exhibited the highest β-cypermethrin-hydrolytic activity at 25 °C and a pH of 7.0, showing robust stability in low and medium temperature environment and a broad range of pH levels. Furthermore, Est13 displayed notable resistance to organic solvents and NaCl, coupled with wide substrate specificity. Moreover, Est13 exhibited substantial efficiency in removing β-cypermethrin residues from various food items such as milk, meat, vegetables, and fruits. These findings underscore the potential of Est13 for application in the bioremediation of pyrethroid-contaminated environments and reduction of pyrethroid residues in food products.

Cometabolic biodegradation system employed subculturing photosynthetic bacteria: A new degradation pathway of 4-chlorophenol in hypersaline wastewater

4-chlorophenol (4-CP) as a toxic persistent pollutant is quite difficult treatment by using traditional biological processes. Herein, photosynthetic bacteria (PSB) driven cometabolic biodegradation system associated with exogeneous carbon sources (e.g., sodium acetate) has been demonstrated as an effective microbial technique. The biodegradation rate (r_i) can be at 0.041 d^-1 with degradation efficiency of 93% in 3094 lx. Through the study of subculturing PSB in absence of NaCl, it was found that 50% inoculation time can be saved but keeping a similar 4-CP biodegradation efficiency in scale-up salinity system. A new plausible biodegradation pathway for 4-CP in 4th G PSB cometabolic system is proposed based on the detected cyclohexanone generation followed by ring opening. It is probably ascribed to the increasement of Firmicutes and Bacteroidetes at phyla level classified based on microbial community. This study contributes to a new insight into cometabolic technology for chlorophenol treatment in industrial hypersaline wastewater.

Dual functional roles of a novel bifunctional β-lactamase/esterase from Lactococcus garvieae

A novel bifunctional β-lactamase/esterase (LgLacI), which is capable of hydrolyzing β-lactam-containing antibiotics including ampicillin, oxacillin, and cefotaxime as well as synthesizing biodiesels, was cloned from Lactococcus garvieae. Unlike most bacterial esterases/lipases that have G-x-S-x-G motif, LgLacI, which contains S-x-x-K catalytic motif, has sequence similarities to bacterial family VIII esterase as well as β-lactamases. The catalytic properties of LgLacI were explored using a wide range of biochemical methods including spectroscopy, assays, structural modeling, mutagenesis, and chromatography. We confirmed the bifunctional property of LgLacI hydrolyzing both esters and β-lactam antibiotics. This study provides novel perspectives into a bifunctional enzyme from L. garvieae, which can degrade β-lactam antibiotics with high esterase activity.

Fabrication and characterization of purified esterase-embedded zeolitic imidazolate frameworks for the removal and remediation of herbicide pollution from soil

The fragility and high cost of enzymes represent critical challenges limiting their practical application in the removal of pesticides. Herein, an aryloxyphenoxypropionate herbicide-hydrolyzing enzyme, QpeH, was purified via one-step affinity chromatography and embedded into two types of zeolitic imidazolate frameworks (ZIFs) through biomimetic mineralization. The catalytic activity towards the herbicide quizalofop-P-ethyl, the loading capacity and efficiency of the resulting two composites, QpeH@ZIF-10 with cruciate flower-like morphology and QpeH@ZIF-8 with rhombic dodecahedral morphology, were compared. Both composites had excellent stability and reusability after 10 reuse cycles, with QpeH@ZIF-10 having a better performance. More importantly, when applied for the removal of quizalofop-P-ethyl pollution in the watermelon field, QpeH@ZIF-10 (88%) showed a remarkably improved degradation efficiency compared to QpeH@ZIF-8 (84%) despite the latter having a greater loading capacity. Finally, the use of QpeH@ZIF composites was shown to recover the bacterial community in soil. This work provides a new insight into the low-cost synthesis of nanobiocatalysts combining simple purified enzymes and metal-organic frameworks (MOFs) for the remediation of pesticide-contaminated soils.

Application of Wickerhamomyces anomalus in Simulated Solid-State Fermentation for Baijiu Production: Changes of Microbial Community Structure and Flavor Metabolism

Wickerhamomyces anomalus is conducive to the synthesis of ester compounds in brewing the Chinese liquor Baijiu; esters are crucial for the quality of Baijiu. In this study, simulated solid-state fermentation for Baijiu production was used to explore whether artificial addition of W. anomalus could improve the flavor substance in Baijiu, and the underlying mechanisms. Two experimental groups were studied, in which W. anomalus Y3604 (Group A) and YF1503 (Group B) were added, respectively; in the control group (Group C), no W. anomalus was added. Adding strain Y3604 increased the content of esters in fermentation samples, especially ethyl acetate and ethyl caproate, and reduced the content of higher alcohols. Adding strain YF1503 had little effect on the ester content but decreased the content of higher alcohols. The diversity and abundance of prokaryotic genera in Group A and B samples were similar, but there were some differences compared with Group C. The correlations of genera in Group A or B samples were simple compared with group C. Although the predominant eukaryotic genera in the three groups were consistent, the abundance of each gene varied among groups. Based on our findings, bioaugmentation of Baijiu fermentation with W. anomalus will change the ethyl acetate content and cause changes in the levels of other flavor substances. We suggest that the changes in flavor substances caused by the addition of W. anomalus are mainly due to changes in the microbial community structure that result from the addition of W. anomalus.

Characterization of a novel carboxylesterase belonging to family VIII hydrolyzing β-lactam antibiotics from a compost metagenomic library

A novel esterase, EstCS3, was isolated from a metagenomic library constructed from a compost. The EstCS3, which consists of 409 amino acids with an anticipated molecular mass of 44 kDa, showed high amino acid sequence identities to predicted esterases, serine hydrolases and β-lactamases from uncultured and cultured bacteria. Phylogenetic analysis suggested that EstCS3 belongs to family VIII of lipolytic enzymes. EstCS3 had catalytic Ser78 residue in the consensus tetrapeptide motif SXXK, which is characteristic of family VIII esterases. Two conserved YXX and W(H or K)XG motifs in an oxyanion hole of family VIII esterases were also present in EstCS3. EstCS3 demonstrated the highest activity toward p-nitrophenyl butyrate (C4) and was stable up to 70 °C with optimal activity at 55 °C. EstCS3 had optimal activity at pH 8 and maintained its stability within pH range of 7-10. EstCS3 had over 70% activity in the presence of 20% (v/v) methanol and DMSO and hydrolyzed sterically hindered tertiary alcohol esters of t-butyl acetate and linalyl acetate. EstCS3 hydrolyzed ampicillin, cephalothin and cefepime. The properties of EstCS3, including moderate thermostability, stability against organic solvents and activity toward esters of tertiary alcohols, indicated that it has the potential to be used in industrial applications.

Identification of the key amino acid sites of the carbofuran hydrolase CehA from a newly isolated carbofuran-degrading strain Sphingbium sp. CFD-1

A novel carbofuran-degrading strain CFD-1 was isolated and preliminarily identified as Sphingbium sp. This strain was able to utilize carbofuran as the sole carbon source for growth. The carbofuran hydrolase gene cehA was cloned from strain CFD-1 and expressed in Escherichia coli. CehA could hydrolyze carbamate pesticides including carbofuran and carbaryl efficiently, while it showed poor hydrolysis ability against isoprocarb, propoxur, oxamyl and aldicarb. CehA displayed maximal enzymatic activity at 40 °C and pH 7.0. The apparent Km and Kcat values of CehA for carbofuran were 133.22 ± 5.70 μM and 9.48 ± 0.89 s-1, respectively. The site-directed mutation experiment showed that His313, His315, His453 and His495 played important roles in the hydrolysis of carbofuran by CehA. Furthermore, the sequence of cehA is highly conserved among different carbofuran-degrading strains, and there are mobile elements around cehA, indicating that it may be transferred horizontally between different strains.

Impact of biosolids, ZnO, ZnO/biosolids on bacterial community and enantioselective transformation of racemic-quizalofop-ethyl in agricultural soil

The effects of biosolids, ZnO, and ZnO/biosolids on soil microorganism and the environmental fate of coexisting racemic-quizalofop-ethyl (rac-QE) were investigated. Microbial biomass carbon in native soil, soil/biosolids decreased by 62% and 52% in the presence of ZnO (2‰, weight ratio). The soil bacterial community structure differed significantly among native soil, soil/biosolids, soil/ZnO, and soil/biosolids/ZnO based on a principal co-ordinate analysis (PCoA) of OTUs and one-way ANOVA test of bacterial genera. Chemical transformation caused by ZnO only contributed 4% and 3% of the overall transformation of R-quizalofop-ethyl (R-QE) and S-quizalofop-ethyl (S-QE) in soil/ZnO. The inhibition effect of ZnO on the initial transformation rate of R-QE (r_R-QE) and S-QE (r_R-QE) in soil only observed when enantiomer concentration was larger than 10 mg/kg. Biosolids embedded with ZnO (biosolids/ZnO) caused a 17%-42% and 22%-38% decrease of r_R-QE and r_S-QE, although r_R-QE and r_S-QE increased by 0%-17% and 22%-58% by the addition of biosolids. The results also demonstrated that the effects of biosolids on agricultural soil microorganism and enantioselective transformation of chiral pesticide was altered by the embedded nanoparticles.

Bioconversion of coal to methane by microbial communities from soil and from an opencast mine in the Xilingol grassland of northeast China

BACKGROUND

The Xilingol grassland ecosystem has abundant superficial coal reserves. Opencast coal mining and burning of coal for electricity have caused a series of environmental challenges. Biogenic generation of methane from coal possesses the potential to improve economic and environmental outcomes of clean coal utilization. However, whether the microbes inhabiting the grassland soil have the functional potential to convert coal into biomethane is still unclear.

RESULTS

Microbial communities in an opencast coal mine and in grassland soil covering and surrounding this mine and their biomethane production potential were investigated by Hiseq sequencing and anaerobic cultivation. The microbial communities in covering soil showed high similarity to those in the surrounding soil, according to the pairwise weighted UniFrac distances matrix. The majority of bacterial communities in coal and soil samples belonged to the phyla Firmicutes, Bacteroidetes, Actinobacteria and Proteobacteria. The dominant bacterial genera in grassland soil included Gaiella, Solirubrobacter, Sphingomonas and Streptomyces; whereas, the most abundant genus in coal was Pseudarthrobacter. In soil, hydrogenotrophic Methanobacterium was the dominant methanogen, and this methanogen, along with acetoclastic Methanosarcina and methylotrophic Methanomassiliicoccus, was detected in coal. Network-like Venn diagram showed that an average of 28.7% of microbial communities in the samples belonged to shared genera, indicating that there is considerable microbial overlap between coal and soil samples. Potential degraders and methanogens in the soil efficiently stimulated methane formation from coal samples by the culturing-based approach. The maximum biogenic methane yields from coal degradation by the microbial community cultured from grassland soil reached 22.4 μmol after 28 day.

CONCLUSION

The potential microbial coal degraders and methanogenic archaea in grassland soil were highly diverse. Significant amounts of biomethane were generated from coal by the addition of grassland soil microbial communities. The unique species present in grassland soil may contribute to efficient methanogenic coal bioconversion. This discovery not only contributes to a better understanding of global microbial biodiversity in coal mine environments, but also makes a contribution to our knowledge of the synthetic microbiology with regard to effective methanogenic microbial consortia for coal degradation.

Carbaryl waste-water treatment by Rhodopseudomonas sphaeroides

Carbaryl wastewater treatment and the resource recycling of biomass as sludge by Rhodopseudomonas sphaeroides (R. sphaeroides) with the assistance of starch processing wastewater (SPW) was investigated in this research. It was observed that carbaryl was not degraded under the 100, 500 mg/L COD groups. The addition of SPW assisted R. sphaeroides to degrade carbaryl efficiently. Carbaryl removal reached 100% after 5 days under the optimal group (3500 mg/L). Interestingly, carbaryl in the mixed wastewater began to be degraded after day 1. Further research indicated that cehA gene was expressed after day 1. Subsequently, carbaryl hydrolase was synthesized under gene regulation. Analysis revealed that cehA and carbaryl hydrolase were adaptive gene expressions and enzymes. Carbaryl as stimulus signal started cehA gene expression through signal transduction pathway. This process took one day for R. sphaeroides. However, organics in 100, 500 mg/L COD groups were deficient, which could not maintain R. sphaeroides growth for over one day. Organics in SPW provided sufficient carbon sources for R. sphaeroides under other groups. The method could complete the mixed (SPW and carbaryl) wastewater treatment, carbaryl removal, the resource recycling of R. sphaeroides biomass as sludge simultaneously.

The removal of cyhalofop-butyl in soil by surplus Rhodopseudanonas palustris in wastewater purification

The biorestoration of cyhalofop-butyl and fertility in soil using Rhodopseudanonas palustris (R. palustris) in the treated wastewater were investigated in this research. Cyhalofop-butyl was not degraded under control group. The treated wastewater containing R. palustris degraded cyhalofop-butyl and remediated fertility. Interestingly, the cyhalofop-butyl-hydrolyzing carboxylesterase gene was expressed after inoculation 24 h. Subsequently, the cyhalofop-butyl-hydrolyzing carboxylesterase were synthesized to degrade cyhalofop-butyl. The cyhalofop-butyl started to be degraded after inoculation 24 h. The cyhalofop-butyl as stimulus signal induced cyhalofop-butyl-hydrolyzing carboxylesterase gene expression through signal transduction pathway. This process took 24 h for R. palustris as they were ancient bacteria. The residual organics in the wastewater provided sufficient carbon sources and energy for R. palustris under three dosage groups. The new method completed the remediation of cyhalofop-butyl pollution, the improvement of soil fertility and soybean processing wastewater treatment simultaneously, and realized the resource reutilization of wastewater and R. palustris as sludge.

Rhodopseudomonas palustris wastewater treatment: Cyhalofop-butyl removal, biochemicals production and mathematical model establishment

Simultaneous (SPW and cyhalofop-butyl) wastewater treatment and the production of biochemicals by Rhodopseudomonas palustris (R. palustris) was investigated with supplementation of soybean processing wastewater (SPW). Compared to control group, cyhalofop-butyl was removed and single cell protein, carotenoid, bacteriochlorophyll productions were enhanced with the supplementation of SPW. Cyhalofop-butyl removal reached 100% after 5 days under 4000 mg/L COD group. Cyhalofop-butyl induced chbH gene expression to synthesize cyhalofop-butyl-hydrolyzing carboxylesterase through activating MAPKKKs, MAPKKs, MAPKs genes in MAPK signal transduction pathway. The induction process took one day for R. palustris. However, lack of organics in original wastewater did not maintain R. palustris growth for over one day. The supplementation of SPW provided sufficient carbon source. This new method resulted in the mixed wastewater treatment and improvement of biochemicals simultaneously, as well as the realization of reutilization of R. palustris. High-order non-linear mathematical model of the relationship between R_chb, X_c, and X_t was established.

Two dcm Gene Clusters Essential for the Degradation of Diclofop-methyl in a Microbial Consortium of Rhodococcus sp. JT-3 and Brevundimonas sp. JT-9

The metabolism of widely used aryloxyphenoxypropionate herbicides has been extensively studied in microbes. However, the information on the degradation of diclofop-methyl (DCM) is limited, with no genetic and biochemical investigation reported. The consortium L1 of Rhodococcus sp. JT-3 and Brevundimonas sp. JT-9 was able to degrade DCM through a synergistic metabolism. To elaborate the molecular mechanism of DCM degradation, the metabolic pathway for DCM was first investigated. DCM was initially transformed by strain JT-3 to diclofop acid and then by strain JT-9 to 2-(4-hydroxyphenoxy) propionic acid as well as 2,4-dichlorophenol. Subsequently, the two dcm gene clusters, dcmAE and dcmB1B2CD, involved in further degradation of 2,4-dichlorophenol, were successfully cloned from strain JT-3, and the functions of each gene product were identified. DcmA, a glutathione-dependent dehalogenase, was responsible for catalyzing the reductive dehalogenation of 2,4-dichlorophenol to 4-chlorophenol, which was then converted by the two-component monooxygenase DcmB1B2 to 4-chlorocatechol as the ring cleavage substrate of the dioxygenase DcmC. In this study, the overall DCM degradation pathway of the consortium L1 was proposed and, particularly, the lower part on the DCP degradation was characterized at the genetic and biochemical levels.

4-Chlorophenol Oxidation Depends on the Activation of an AraC-Type Transcriptional Regulator, CphR, in Rhodococcus sp. Strain YH-5B

4-Chlorophenol (4-CP) oxidation plays an essential role in the detoxification of 4-CP. However, oxidative regulation of 4-CP at the genetic and biochemical levels has not yet been studied. To explore the regulation mechanism of 4-CP oxidation, a novel gene cluster, cphRA2A1, involved in biodegradation of 4-CP was identified and cloned from Rhodococcus sp. strain YH-5B by genome walking. The sequence analysis showed that the cphRA2A1 gene cluster encoded an AraC-type transcriptional regulator and a two-component monooxygenase enzyme, while quantitative real-time PCR analysis further revealed that cphR was constitutively expressed and positively regulated the transcription of cphA2A1 genes in response to 4-CP or phenol, as evidenced by gene knockout and complementation experiments. Through the transcriptional fusion of the mutated cphA2A1 promoter with the lacZ gene, it was found that the CphR regulator binding sites had two 15-bp imperfect direct repeats (TGCA-N6-GGNTA) at -35 to -69 upstream of the cphA2A1 transcriptional start site. Notably, the sub-motifs at the -46 to -49 positions played a critical role in the appropriate interaction with the CphR dimer. In addition, it was confirmed that the monooxygenase subunits CphA1 and CphA2, which were purified by His-tag affinity chromatography, were able to catalyze the conversion of 4-CP to 4-chlorocatechol, suggesting that strain YH-5B could degrade 4-CP via the 4-chlorocatechol pathway. This study enhances our understanding of the genetic and biochemical diversity in the transcriptional regulation of 4-CP oxidation in Gram-positive bacteria.

Biodegradation of bispyribac sodium by a novel bacterial consortium BDAM: Optimization of degradation conditions using response surface methodology

Bispyribac sodium (BS), is a selective, systemic and post emergent herbicide used to eradicate grasses and broad leaf weeds. Extensive use of this herbicide has engendered serious environmental concerns. Hence it is important to develop strategies for bioremediation of BS in a cost effective and environment friendly way. In this study a bacterial consortium named BDAM, comprising three novel isolates Achromobacter xylosoxidans (BD1), Achromobacter pulmonis (BA2), and Ochrobactrum intermedium (BM2), was developed by virtue of its potential for degradation of BS. Different culture conditions (temperature, pH and inoculum size) were optimized for degradation of BS by the consortium BDAM and the mutual interactions of these parameters were analysed using a 2³ full factorial central composite design (CCD) based on Response Surface Methodology (RSM). The optimal values for temperature, pH and inoculum size were found to be 40 °C, 8 and 0.4 g/L respectively to achieve maximum degradation of BS (85.6%). Moreover, the interactive effects of these parameters were investigated using three dimensional surface plots in terms of maximum fitness function. Importantly, it was concluded that the newly developed consortium is a potential candidate for biodegradation of BS in a safe, cost-effective and environmentally friendly manner.

Purification and properties of a novel quizalofop-p-ethyl-hydrolyzing esterase involved in quizalofop-p-ethyl degradation by Pseudomonas sp. J-2

Quizalofop-p-ethyl (QPE) is a post-emergence herbicide that effectively controls grass weeds and is often detected in the environment. However, the biochemical and molecular mechanisms of QPE degradation in the environment remains unclear. In this study, a highly effective QPE-degrading bacterial strain J-2 was isolated from acclimated activated sludge and identified as a Pseudomonas sp., containing the QPE breakdown metabolite quizalofop acid (QA) identified by Liquid Chromatography-Ion Trap-Mass Spectrometry (LC-IT-MSⁿ) analysis. A novel QPE hydrolase esterase-encoding gene qpeH was cloned from strain J-2 and functionally expressed in Escherichia coli BL21 (DE3). The specific activity of recombinant QpeH was 198.9 ± 2.7 U mg⁻¹ for QPE with K_m and K_cat values of 41.3 ± 3.6 μM and 127.3 ± 4.5 s⁻¹. The optimal pH and temperature for the recombinant QpeH were 8.0 and 30 °C, respectively and the enzyme was activated by Ca²⁺, Cd²⁺, Li⁺, Fe³⁺ and Co²⁺ and inhibited by Ni²⁺, Fe²⁺, Ag⁺, DEPC, SDS, Tween 80, Triton X, β-mercaptoethanol, PMSF, and pCMB. In addition, the catalytic efficiency of QpeH toward different AOPP herbicides in descending order was as follows: fenoxaprop-P-ethyl > quizalofop-P-tefuryl > QPE > haloxyfop-P-methyl > cyhalofopbutyl > clodinafop-propargyl. On the basis of the phylogenetic analysis and multiple sequence alignment, the identified enzyme QpeH, was clustered with esterase family V, suggesting a new member of this family because of its low similarity of amino acid sequence with esterases reported previously.

Enhanced treatment performance of coking wastewater and reduced membrane fouling using a novel EMBR

A novel EMBR (electric field applied in MBR) by placing stainless steel mesh cathode inside a flat membrane module and stainless steel mesh anode outside the module was built and operated to enhance the treatment performance of coking wastewater containing phenol, pyridine and quinoline and reduce the membrane fouling. The degradation rates of COD, phenol, pyridine and quinoline in EMBR with electric field (reactor A) were significantly higher than the sum of EMBR without electric field (reactor B) and only electro-catalytic degradation during the long-term treatment, confirming that a coupling effect was existed between biodegradation and electro-catalytic degradation process. Illumina sequencing data revealed that bacterial community was richer and more diverse in reactor A. Comamonas strain JB as the inoculums was the most dominant genus in each reactor and electric field applied in reactor A further improved the abundance of strain JB. The membrane fouling in reactor A was reduced.