Elucidating the impacts of cobalt (II) ions on extracellular electron transfer and pollutant degradation by anodic biofilms in bioelectrochemical systems during industrial wastewater treatment

Electrogenic biofilms in bioelectrochemical systems (BES) are critical in wastewater treatment. Industrial effluents often contain cobalt (Co2+); however, its impact on biofilms is unknown. This study investigated how increasing Co2+ concentrations (0-30 mg/L) affect BES biofilm community dynamics, extracellular polymeric substances, microbial metabolism, electron transfer gene expression, and electrochemical performance. The research revealed that as Co2+ concentrations increased, power generation progressively declined, from 345.43 ± 4.07 mW/m2 at 0 mg/L to 160.51 ± 0.86 mW/m2 at 30 mg/L Co2+. However, 5 mg/L Co2+ had less effect. The Co2+ removal efficiency in the reactors fed with 5 and 10 mg/L concentrations exceeded 99% and 94%, respectively. However, at 20 and 30 mg/L, the removal efficiency decreased substantially, likely because of reduced biofilm viability. FTIR indicated the participation of biofilm functional groups in Co2+ uptake. XPS revealed Co2+ presence in biofilms as CoO and Co(OH)2, indicating precipitation also aided removal. Cyclic voltammetry and electrochemical impedance spectroscopy tests revealed that 5 mg/L Co2+ had little impact on the electrocatalytic activity, while higher concentrations impaired it. Furthermore, at a concentration of 5 mg/L Co2+, there was an increase in the proportion of the genus Anaeromusa-Anaeroarcus, while the genus Geobacter declined at all tested Co2+ concentrations. Additionally, higher concentrations of Co2+ suppressed the expression of extracellular electron transfer genes but increased the expression of Co2+-resistance genes. Overall, this study establishes how Co2+ impacts electrogenic biofilm composition, function, and treatment efficacy, laying the groundwork for the optimized application of BES in remediating Co2+-contaminated wastewater.

Enlarging the substrate binding pocket of penicillin G acylase from Achromobacter sp. for highly efficient biosynthesis of β-lactam antibiotics

Penicillin G acylase (PGA) is a key biocatalyst for the enzymatic production of β-lactam antibiotics, which can not only catalyze the synthesis of β-lactam antibiotics but also catalyze the hydrolysis of the products to prepare semi-synthetic antibiotic intermediates. However, the high hydrolysis and low synthesis activities of natural PGAs severely hinder their industrial application. In this study, a combinatorial directed evolution strategy was employed to obtain new PGAs with outstanding performances. The best mutant βF24G/βW154G was obtained from the PGA of Achromobacter sp., which exhibited approximately a 129.62-fold and a 52.55-fold increase in specific activity and synthesis/hydrolysis ratio, respectively, compared to the wild-type AsPGA. Thereafter, this mutant was used to synthesize amoxicillin, cefadroxil, and ampicillin; all conversions > 99% were accomplished in 90-135 min with almost no secondary hydrolysis byproducts produced in the reaction. Molecular dynamics simulation and substrate pocket calculation revealed that substitution of the smallest glycine residue at βF24 and βW154 expanded the binding pocket, thereby facilitating the entry and release of substrates and products. Therefore, this novel mutant is a promising catalyst for the large-scale production of β-lactam antibiotics.

Antimony oxidation and whole genome sequencing of Phytobacter sp. X4 isolated from contaminated soil near a flotation site

The conversion of the more toxic Sb(III) into less toxic Sb(V) is an effective strategy for the treatment of antimony-contaminated sites. In this study, a strain, Phytobacter sp. X4, which can tolerate high concentrations of antimony and can use nitrate as an electron acceptor for Sb(III) oxidation under anaerobic conditions, was isolated from the deep soil of an antimony mine flotation tailing. Unlike other antimony oxidizing bacteria, X4 oxidized better under high Sb(III) concentration, and the oxidation efficiency of 10 mM Sb(III) reached the maximum at 110 h with 61.8 %. Kinetic study showed X4 yielded a V_max of 1.093 μM∙min^-1 and a K_m of 718.2 μM. The genome of Phytobacter sp. X4 consists of a complete circular chromosome and two plasmids. In addition, X4 had more metal(loid)s resistance genes and highly expressed genes than other Phytobacter spp., reflecting its stronger adaptive advantage in harsh survival environments. We also analyzed the origin and evolution of arsB, arsC, and arsH, which may have been transferred horizontally from other species. iscR and arsH may have an important contribution to Sb(III) oxidation. Thus, Phytobacter sp. X4 has a good ability to remediate high antimony-contaminated sites and can be applied to an anaerobic environment.

Heterotrophic anodic denitrification coupled with cathodic metals recovery from on-site smelting wastewater with a bioelectrochemical system inoculated with mixed Castellaniella species

Although Castellaniella species are crucial for denitrification, there is no report on their capacity to carry out denitrification and anode respiration simultaneously in a bioelectrochemical system (BES). Herein, the ability of a mixed inoculum of electricigenic Castellaniella species to perform simultaneous denitrification and anode respiration coupled with cathodic metals recovery was investigated in a BES. Results showed that 500 mg/L NO₃^--N significantly decreased power generation, whereas 100 and 250 mg/L NO₃^--N had a lesser impact. The single-chamber MFCs (SCMFCs) fed with 100 and 250 mg/L NO₃^--N concentrations achieved a removal efficiency higher than 90% in all cycles. In contrast, the removal efficiency in the SCMFCs declined dramatically at 500 mg/L NO₃^--N, which might be attributable to decreased microbial viability as revealed by SEM and CLSM. EPS protein content and enzymatic activities of the biofilms decreased significantly at this concentration. Cyclic voltammetry results revealed that the 500 mg/L NO₃^--N concentration decreased the redox activities of anodic biofilms, while electrochemical impedance spectroscopy showed that the internal resistance of the SCMFCs at this concentration increased significantly. In addition, BES inoculated with the Castellaniella species was able to simultaneously perform heterotrophic anodic denitrification and cathodic metals recovery from real wastewater. The BES attained Cu²⁺, Hg²⁺, Pb²⁺, and Zn²⁺ removal efficiencies of 99.86 ± 0.10%, 99.98 ± 0.014%, 99.98 ± 0.01%, and 99.17 ± 0.30%, respectively, from the real wastewater. Cu²⁺ was bio-electrochemically reduced to Cu⁰ and Cu₂O, whereas Hg⁰ and HgO constituted the Hg species recovered via bioelectrochemical reduction and chemical deposition, respectively. Furthermore, Pb²⁺ and Zn²⁺ were bio-electrochemically reduced to Pb⁰ and Zn⁰, respectively. Over 89% of NO₃^--N was removed from the BES anolyte during the recovery of the metals. This research reveals promising denitrifying exoelectrogens for enhanced power generation, NO₃^--N removal, and heavy metals recovery in BES.

Sequence and structure-guided discovery of a novel NADH-dependent 7β-hydroxysteroid dehydrogenase for efficient biosynthesis of ursodeoxycholic acid

7β-Hydroxysteroid dehydrogenases (7β-HSDHs) have attracted increasing attention due to their crucial roles in the biosynthesis of ursodeoxycholic acid (UDCA). However, most published 7β-HSDHs are strictly NADPH-dependent oxidoreductases with poor activity and low productivity. Compared with NADPH, NADH is more stable and cheaper, making it the more popular cofactor for industrial applications of dehydrogenases. Herein, by using a sequence and structure-guided genome mining approach based on the structural information of conserved cofactor-binding motifs, we uncovered a novel NADH-dependent 7β-HSDH (Cle7β-HSDH). The Cle7β-HSDH was overexpressed, purified, and characterized. It exhibited high specific activity (9.6 U/mg), good pH stability and thermostability, significant methanol tolerance, and showed excellent catalytic efficiencies (k_cat/K_m) towards 7-oxo-lithocholic acid (7-oxo-LCA) and NADH (70.8 mM^-1s^-1 and 31.8 mM^-1s^-1, respectively). Molecular docking and mutational analyses revealed that Asp42 could play a considerable role in NADH binding and recognition. Coupling with a glucose dehydrogenase for NADH regeneration, up to 20 mM 7-oxo-LCA could be completely transformed to UDCA within 90 min by Cle7β-HSDH. This study provides an efficient approach for mining promising enzymes from genomic databases for cost-effective biotechnological applications.

Evaluation of fungal community assembly and function during food waste composting with Aneurinibacillus sp. LD3 inoculant

The objective of this work was to evaluate the fungal community assembly and function during food waste composting with Aneurinibacillus sp. LD3 (LD3) inoculant. Inoculation reduced the content of total organic carbon, moisture content, nitrate nitrogen, and nitrite nitrogen. The LD3 inoculant was able to drive the changes in the assembly of the fungal community. In particular, inoculation with LD3 not only increased the relative abundance of Ascomycota and Trichocomaceae_unclassified for lignocellulose degradation at the mesophilic and cooling stages but also reduced the relative abundances of the opportunistic human pathogen Candida. Saprotroph was the predominant fungal trophic mode in composting, and inoculation with LD3 has a better inactivation effect on animal and plant pathogenic fungi during composting. Furthermore, the variation of the fungal community after inoculation with LD3 was the largest explained by temperature (30.64%). These results implied that LD3 significantly regulated fungal composition and function of food waste composting.

Isolation and characterization of a novel thermotolerant alkali lignin-degrading bacterium Aneurinibacillus sp. LD3 and its application in food waste composting

The aim of this study was to isolate thermotolerant alkali lignin-degrading bacteria and to investigate their degradation characteristics and application in food waste composting. Two thermotolerant alkali lignin-degrading bacteria isolates were identified as Bacillus sp. LD2 (LD2) and a novel species Aneurinibacillus sp. LD3 (LD3). Compared with strain LD2, LD3 had a higher alkali lignin degradation rate (61.28%) and ligninolytic enzyme activities, and the maximum lignin peroxidase, laccase, and manganese peroxidase activities were 3117.25, 1484.5, and 1770.75 U L^-1, respectively. GC-MS analysis revealed that low-molecular-weight compounds such as 4'-hydroxy-3'-methoxy acetophenone, vanillic acid, 1-(4-hydroxy-3,5-dimethoxyphenyl), benzoic acid, and octadecanoic acid were formed in the degradation of alkali lignin by LD3, indicating the cleavage of β-aryl ether, C_α-C_β bonds, and aromatic rings in lignin. Composting results showed that inoculating LD3 improved the degradation of organic matter by 20.11% and reduced the carbon-to-nitrogen (C/N) ratio (15.66). Additionally, a higher decrease in the content of lignocellulose was observed in the LD treatment. FTIR and 3D-EEM spectra analysis indicated that inoculating LD3 promoted the decomposition of easily available organic substances and lignocellulose and the formation of aromatic structures and humic acid-like substances. In brief, the thermotolerant lignin-degrading bacterium Aneurinibacillus sp. LD3 is effective in degrading lignin and improving the quality of composting.

Exploring the dynamic of microbial community and metabolic function in food waste composting amended with traditional Chinese medicine residues

The aim of this study was to explore the dynamic of microbial community and metabolic function in food waste composting amended with traditional Chinese medicine residues (TCMRs). Results suggested that TCMRs addition at up to 10% leads to a higher peak temperature (60.5 °C), germination index (GI) value (119.26%), and a greater reduction in total organic carbon (TOC) content (8.08%). 10% TCMRs significantly induced the fluctuation of bacterial community composition, as well as the fungal community in the thermophilic phase. The addition of 10% TCMRs enhanced the abundance of bacterial genera such as Acetobacter, Bacillus, and Brevundimonas, as well as fungal genera such as Chaetomium, Thermascus, and Coprinopsis, which accelerated lignocellulose degradation and humification degree. Conversely, the growth of Lactobacillus and Pseudomonas was inhibited by 10% TCMRs to weaken the acidic environment and reduce nitrogen loss. Metabolic function analysis revealed that 10% TCMRs promoted the metabolism of carbohydrate and amino acid, especially citrate cycle, glycolysis/gluconeogenesis, and cysteine and methionine metabolism. Redundancy analysis showed that the carbon to nitrogen (C/N) ratio was the most significant environmental factor influencing the dynamic of bacterial and fungal communities.

Insight into the microbial mechanisms for the improvement of composting efficiency driven by Aneurinibacillus sp. LD3

This work explored the microbial mechanisms for the improvement of composting efficiency driven by thermotolerant lignin-degrading bacterium Aneurinibacillus sp. LD3 (LD3). Results showed that LD3 inoculant prolonged the thermophilic period by 4 days, improved the final content of humic acid, total phosphorus (TP), nitrogen, potassium and seed germination index. Inoculating LD3 enhanced the relative abundance of thermotolerant and phosphate-solubilizing microbes including the phyla of Proteobacteria, Bacteroidota, Firmicutes, and Actinobacteriota, and the genus of Bacillus, Thermoactinomyces, and Pseudomonas. Metabolic function analysis showed that sequences involved in carbohydrate and amino acid metabolism were boosted, while sequences associated with human disease were reduced after inoculating LD3. Spearman correlation analysis revealed that Aneurinibacillus has a significant positive correlation with temperature, TP, Bacillus, and Thermoactinomyces. This study provides useful information for understanding the microbial mechanisms of LD3 promoting composting efficiency, and reveals the tremendous potential of LD3 in the resource utilization of organic solid wastes.

The cytoplasmic tail substitution increases the assembly efficiency of Ebola virus glycoprotein on the budded virus of Bombyx mori nucleopolyhedrovirus

Glycoprotein (GP_1,2) of the Ebola virus (EBOV) is the key membrane fusion protein, which is a key candidate protein for vaccine preparations. Previously, GP_1,2 was expressed by Bombyx mori nucleopolyhedrovirus (BmNPV) expression vector system; however, few GP_1,2 was incorporated into budded virus (BV) of BmNPV. To improve the incorporation efficiency of GP_1,2 into the virion, the GP_1,2 fusion with the cytoplasmic tail of GP64 of BmNPV was expressed in BmN cells by the BmNPV expression system. The BV was purified by ultracentrifugation, and GP_1,2 expression in BV was detected by the antibody. The result indicated that a 532% increase in the relative GP_1,2 densitometry signal was observed in constructs utilizing the GP64 C-terminal domain; moreover, the substitution of GP_1,2 native signal peptide with GP64 signal peptide increased the incorporation efficiency by 34.6% in the relative GP_1,2 densitometry signal. We revealed that the application of the cytoplasmic tail of BmNPV GP64 significantly increased the incorporation rate of GP_1,2 into the BV envelope. This study lays a foundation for GP_1,2 vaccine development.

Effect of nickel (II) on the performance of anodic electroactive biofilms in bioelectrochemical systems

The impact of nickel (Ni²⁺) on the performance of anodic electroactive biofilms (EABs) in the bioelectrochemical system (BES) was investigated in this study. Although it has been reported that Ni²⁺ influences microorganisms in a number of ways, it is unknown how its presence in the anode of a BES affects extracellular electron transfer (EET) of EABs, microbial viability, and the bacterial community. Results revealed that the addition of Ni²⁺ decreased power output from 673.24 ± 12.40 mW/m² at 0 mg/L to 179.26 ± 9.05 mW/m² at 80 mg/L. The metal and chemical oxygen demand removal efficiencies of the microbial fuel cells (MFCs) declined as Ni²⁺ concentration increased, which could be attributed to decreased microbial viability as revealed by SEM and CLSM. FTIR analysis revealed the involvement of various microbial biofilm functional groups, including hydroxyl, amides, methyl, amine, and carboxyl, in the uptake of Ni²⁺. The presence of Ni²⁺ on the anodic biofilms was confirmed by SEM-EDS and XPS analyses. CV demonstrated that the electron transfer performance of the anodic biofilms was negatively correlated with the various Ni²⁺ concentrations. EIS showed that the internal resistance of the MFCs increased with increasing Ni²⁺ concentration, resulting in a decrease in power output. High-throughput sequencing results revealed a decrease in Geobacter and an increase in Desulfovibrio in response to Ni²⁺ concentrations of 10, 20, 40, and 80 mg/L. Furthermore, the various Ni²⁺ concentrations decreased the expression of EET-related genes. The Ni²⁺-fed MFCs had a higher abundance of the nikR gene than the control group, which was important for Ni²⁺ resistance. This work advances our understanding of Ni²⁺ inhibition on EABs, as well as the concurrent removal of organic matter and Ni²⁺ from wastewater.

Microbial community structures and their driving factors in a typical gathering area of antimony mining and smelting in South China

This study investigated soil microbial community in a typical gathering area of antimony mining and smelting in South China. The physical and chemical properties of different soils (mining waste dumps, flotation tailings, and smelting slag) and depths (0-20 cm, 40-60 cm, and 80-100 cm) were compared. The results showed that antimony (Sb) and arsenic (As) were the main pollutants, and their concentrations were 5524.7 mg/kg and 3433.7 mg/kg, respectively. Xanthates were found in the flotation tailings and smelting slag, and the highest concentration was 585.1 mg/kg. The microbial communities were analyzed by high-throughput sequencing, and it was shown that Proteobacteria, Acidobacteria, Chlorobacterium, Bacteroides, and Actinomycetes were the dominant taxa at the phylum level. There were obvious differences in microbial community structure in different sites. The dominant microorganism in the mining site was Chujaibacter. Subgroup_2_unclassified and Gemmatimonadaceae_unclassified were the prevalent microorganisms in the flotation and smelting sites, respectively. As, Sb, and xanthates were the main factors affecting the diversity and composition of bacteria in the flotation tailings and smelting slag areas. Therefore, this study provides experimental guidance and a theoretical basis for soil antimony pollution quality assessment, biological treatment, and environmental remediation.

Recovery of heavy metals from industrial wastewater using bioelectrochemical system inoculated with novel Castellaniella species

Water pollution is a global issue that has drastically increased in recent years due to rapid industrial development. Different technologies have been designed for the removal of pollutants from wastewater. However, most of these techniques are expensive, generate new waste, and focus solely on metal removal instead of metal recovery. In this study, novel facultative exoelectrogenic strains designated Castellaniella sp. A5, Castellaniella sp. B3, and Castellaniella sp. A3 were isolated from a microbial fuel cell (MFC). These isolates were utilized as pure and mixed culture inoculums in a bioelectrochemical system (BES) to produce bioelectricity and treat simulated industrial wastewater. A single-chamber MFC inoculated with the mixed culture attained the highest electricity generation (i.e., 320 mW/m² power density and 3.19 A/m² current density), chemical oxygen demand removal efficiency (91.15 ± 0.05%), and coulombic efficiency (54.81 ± 4.18%). In addition, the BES containing biofilms of the mixed culture achieved the highest Cu, Cr, and Cd removal efficiencies of 99.89 ± 0.07%, 99.59 ± 0.53%, and 99.91 ± 0.04%, respectively. The Cr⁶⁺ and Cu²⁺ in the simulated industrial wastewater were recovered via microbial electrochemical reduction as Cr³⁺ and Cu⁰, respectively. However, Cd²⁺ precipitated as Cd (OH)₂ or CdCO₃ on the surface of the cathodes. These results suggest that a mixed culture inoculum of Castellaniella sp. A5, Castellaniella sp. B3, and Castellaniella sp. A3 has great potential as a biocatalyst in BES for heavy metals recovery from industrial wastewater.

Enhancing microbial fuel cell performance using anode modified with Fe3O4 nanoparticles

Low electricity generation efficiency is one of the key issues that must be addressed for the practical application of microbial fuel cells (MFCs). Modification of microbial electrode materials is an effective method to enhance electron transfer. In this study, magnetite (Fe₃O₄) nanoparticles synthesized by co-precipitation were added to anode chambers in different doses to explore its effect on the performance of MFCs. The maximum power density of the MFCs doped with 4.5 g/L Fe₃O₄ (391.11 ± 9.4 mW/m²) was significantly increased compared to that of the undoped MFCs (255.15 ± 24.8 mW/m²). The COD removal efficiency of the MFCs increased from 85.8 ± 2.8% to 95.0 ± 2.1%. Electrochemical impedance spectroscopy and cyclic voltammetry tests revealed that the addition of Fe₃O₄ nanoparticles enhanced the biocatalytic activity of the anode. High-throughput sequencing results indicated that 4.5 g/L Fe₃O₄ modified anodes enriched the exoelectrogen Geobacter (31.5%), while control MFCs had less Geobacter (17.4%). Magnetite is widely distributed worldwide, which provides an inexpensive means to improve the electrochemical performance of MFCs.

A novel polysaccharides-based bioflocculant produced by Bacillus subtilis ZHX3 and its application in the treatment of multiple pollutants

A high bioflocculant-producing bacterial strain was identified and named Bacillus subtilis ZHX3. Single-factor experiments suggested that 10 g/L starch and 5 g/L yeast extract were optimal for strain ZHX3 to produce bioflocculant MBF-ZHX3. The maximum flocculating rate reached 95.5%, and 3.14 g/L product was extracted after 3 days of cultivation. MBF-ZHX3 was mainly composed of polysaccharides (77.2%) and protein (14.8%). The polysaccharides contained 28.9% uronic acid and 3.7% amino sugar. Rhamnose, arabinose, galactose, glucose, mannose, and galacturonic acid in a molar ratio of 0.35:1.83:3.09:12.66:0.46:3.81 were detected. MBF-ZHX3 had a molecular weight of 10,028 Da and contained abundant groups (-OH, CO, >PO, C-O-C) contributing to flocculation. Adsorption and bridging was considered as the main flocculation mechanism. MBF-ZHX3 was more effective in decolorizing dyes, removing heavy metals and flotation reagents compared to polyacrylamide. The results implied that MBF-ZHX3 has the potential to substitute polyacrylamide in wastewater treatment because of its excellent biological and environmental benefits.

Impact of bamboo sphere amendment on composting performance and microbial community succession in food waste composting

The purpose of this study was to find an economical and effective amendment for improving composting performance and product quality, as well as to analyze the microbial community succession in the whole phase of composting. Therefore, the effect of reusable amendment bamboo sphere on composting performance and microbial community succession during food waste composting was investigated. The results showed that 6% bamboo sphere treatment had the highest degree of polymerization (3.7) and humification index (0.18). Compared with control, 6% bamboo sphere amendment increased total nitrogen (TN), phosphorus (TP) and potassium (TK) contents by 13.61%, 19% and 17.42%, respectively. Furthermore, bamboo sphere enhanced bacterial-fungal diversity and improved microbial community composition by enhancing the relative abundance of thermo-tolerance and lignocellulolytic bacteria and fungi. The five most abundant genera in bamboo sphere composting comprised Bacillus (0-71.47%), Chloroplast-norank (0-47.17%), Pusillimonas (0-33.24%), Acinetobacter (0-27.98%) and unclassified Sphingobacteriaceae (0-22.62%). Linear discriminant analysis effect size showed that Firmicutes, Thermoascaceae and Actinobacteriota, which have a relationship with the decomposition of soluble organic matter and lignocellulose, were significantly enriched in bamboo sphere treatment. Canonical correspondence analysis illustrated that total organic carbon (TOC), TK, and TP were the most important environmental factors on microbial community succession in the two composting systems. Together these results suggest that bamboo sphere as a reusable amendment can shorten maturity period, improve humification degree, increase the contents of nutrient and contribute to the succession of microbial community during food waste composting. These findings provide a theoretical basis for improving the efficiency of food waste composting.

Effect of bamboo sphere amendment on the organic matter decomposition and humification of food waste composting

The aim of this study is to examine the effect of bamboo sphere on the organic matter decomposition and humification of food waste composting. Food waste composting were carried out on four treatments, namely control (CK), 3% (T1), 6% (T2) and 9% (T3) (w/w) bamboo sphere treatments. Results showed that adding bamboo sphere facilitated the organic matter decomposition and increased the seed germination index. The number of cells in T2 treatment was always the highest during the composting process. Furthermore, the final humic substances and humic acid contents increased by 41.08% and 68.3%, respectively, in 6% bamboo sphere treatment. Fourier transform infrared and excitation-emission matrix fluorescence spectroscopy analysis revealed that adding bamboo sphere accelerated the humification of composting with more aromatic structures and humic acid-like substances. GC-MS studies revealed that the compost products of 6% bamboo sphere treatment had more ring structures, and thus enhanced the humification.

Evolutionary, genomic, and biogeographic characterization of two novel xenobiotics-degrading strains affiliated with Dechloromonas

Xenobiotics are generally known as man-made refractory organic pollutants widely distributed in various environments. For exploring the bioremediation possibility of xenobiotics, two novel xenobiotics-degrading strains affiliated with Azonexaceae were isolated. We report here the phylogenetics, genome, and geo-distribution of a novel and ubiquitous Azonexaceae species that primarily joins in the cometabolic process of some xenobiotics in natural communities. Strains s22 and t15 could be proposed as a novel species within Dechloromonas based on genomic and multi-phylogenetic analysis. Pan-genome analysis showed that the 63 core genes in Dechloromonas include genes for dozens of metabolisms such as nitrogen fixation protein (nifU), nitrogen regulatory protein (glnK), dCTP deaminase, C4-dicarboxylate transporter, and fructose-bisphosphate aldolase. Strains s22 and t15 have the ability to metabolize nitrogen, including nitrogen fixation, NirS-dependent denitrification, and dissimilatory nitrate reduction. Moreover, the novel species possesses the EnvZ-OmpR two-component system for controlling osmotic stress and QseC-QseB system for quorum sensing to rapidly sense environmental changes. It is intriguing that this new species has a series of genes for the biodegradation of some xenobiotics such as azathioprine, 6-Mercaptopurine, trinitrotoluene, chloroalkane, and chloroalkene. Specifically, glutathione S-transferase (GST) and 4-oxalocrotonate tautomerase (praC) in this novel species play important roles in the detoxification metabolism of some xenobiotics like dioxin, trichloroethene, chloroacetyl chloride, benzo[a]pyrene, and aflatoxin B1. Using data from GenBank, DDBJ and EMBL databases, we also demonstrated that members of this novel species were found globally in plants (e.g. rice), guts (e.g. insect), pristine and contaminated regions. Given these data, Dechloromonas sp. strains s22 and t15 take part in the biodegradation of some xenobiotics through key enzymes.

Bioactive components from Moringa oleifera seeds: production, functionalities and applications - a critical review

A readily distinguishable and indigenous member of the plant kingdom in the Indian subcontinent is the 'drumstick tree', i.e. Moringa oleifera Lam. In addition to India, this drought-tolerant and rapidly evolving tree is currently extensively disseminated across the globe, including subtropical and tropical areas. The plant boasts a high nutritional, nutraceutical and therapeutic profile, mainly attributing to its significant repertoire of the biologically active components in different parts: protein, flavonoids, saponins, phenolic acids, tannin, isothiocyanate, lipids, minerals, vitamins, amongst others. M. oleifera seeds have been shown to elicit a myriad of pharmacological potential and health benefits, including: antimicrobial, anticancer, antidiabetic, antioxidant, antihypertensive, anti-inflammatory and cardioprotective properties. Additionally, the seed cakes obtained from post-extraction process are utilized for: coagulation, flocculation and sedimentation purposes, benefiting effluent management and the purification of water, mainly because of their capability in eliminating microbes and organic matter. Despite the extraordinary focus on other parts of the plant, especially the foliage, the beneficial aspects of the seeds have not been sufficiently highlighted. The health benefits of bioactive components in the seeds are promising and demonstrate enough potential to facilitate the development of functional foods. In this review, we present a critical account of the types, characteristics, production and isolation of bioactive components from M. oleifera seeds. Furthermore, we appraise the: pharmacological activities, cosmetic, biodiesel, lubricative, modern farming, nutritive and wastewater treatment applications of these functional ingredients. We infer that there is a need for further human/clinical studies and evaluation, despite their health benefits. Additionally, the safety issues need to be adequately clarified and assessed, in order to establish a conventional therapeutic profile.

Construction of a Tetracycline Degrading Bacterial Consortium and Its Application Evaluation in Laboratory-Scale Soil Remediation

As an environmental pollutant, tetracycline (TC) can persist in the soil for years and damage the ecosystem. So far, many methods have been developed to handle the TC contamination. Microbial remediation, which involves the use of microbes to biodegrade the pollutant, is considered cost-efficient and more suitable for practical application in soil. This study isolated several strains from TC-contaminated soil and constructed a TC-degrading bacterial consortium containing Raoultella sp. XY-1 and Pandoraea sp. XY-2, which exhibited better growth and improved TC degradation efficiency compared with single strain (81.72% TC was biodegraded within 12 days in Lysogeny broth (LB) medium). Subsequently, lab-scale soil remediation was conducted to evaluate its effectiveness in different soils and the environmental effects it brought. Results indicated that the most efficient TC degradation was recorded at 30 °C and in soil sample Y which had relatively low initial TC concentration (around 35 mg/kg): TC concentration decreased by 43.72% within 65 days. Soil properties were affected, for instance, at 30 °C, the pH value of soil sample Y increased to near neutral, and soil moisture content (SMC) of both soils declined. Analysis of bacterial communities at the phylum level showed that Proteobacteria, Bacteroidetes, Acidobacteria, and Chloroflexi were the four dominant phyla, and the relative abundance of Proteobacteria significantly increased in both soils after bioremediation. Further analysis of bacterial communities at the genus level revealed that Raoultella sp. XY-1 successfully proliferated in soil, while Pandoraea sp. XY-2 was undetectable. Moreover, bacteria associated with nitrogen cycling, biodegradation of organic pollutants, soil biochemical reactions, and plant growth were affected, causing the decline in soil bacterial diversity. Variations in the relative abundance of tetracycline resistance genes (TRGs) and mobile gene elements (MGEs) were investigated, the results obtained indicated that tetD, tetG, tetX,intI1, tnpA-04, and tnpA-05 had higher relative abundance in original soils, and the relative abundance of most TRGs and MGEs declined after the microbial remediation. Network analysis indicated that tnpA may dominate the transfer of TRGs, and Massilia, Alkanibacter, Rhizomicrobium, Xanthomonadales, Acidobacteriaceae, and Xanthomonadaceae were possible hosts of TRGs or MGEs. This study comprehensively evaluated the effectiveness and the ecological effects of the TC-degrading bacterial consortium in soil environment.