The potential arsenite bioteansformation activity of arsenic was investigated by examining bacterial arsenic arsenite-oxidizing gene such as aoxS, aoxR, aoxA, aoxB, aoxC, and aoxD in high arsenic-contaminated drinking water produced from the surface water of floating houses. There is a biogeochemical cycle of activity involving arsenite oxidase aox system and the ars (arsenic resistance system) gene operon and aoxR leader gene activity in Alcaligenes faecalis SRR-11 and aoxS leader gene activity in Achromobacter xylosoxidans TSL-66. Batch experiments showed that SRR-11 and TSL-66 completely oxidized 1 mM of As (III) to As (V) within 35–40 h. The leaders of aoxS and aoxR are important for gene activity, and their effects in arsenic bioremediation and mobility in natural water has a significant ecological role because it allows arsenite oxidase in bacteria to control the biogeochemical cycle of arsenic-contaminated drinking water produced from surface water of floating houses.

Microorganisms are frequently exposed to flowing fluid, thus to investigate bacterial characteristics under different hydrodynamic conditions is of great importance in microbial ecology. This study characterized bacterial growth and phenol biodegradation of three strains, i.e., Microbacterium oxydans (rod-shaped, non-motile), Alcaligenes faecalis (rod-shaped, motile), and Staphylococcus haemolyticus (spherical, non-motile) in shake-flask cultures at various rotating speeds. For all the strains, a higher rotating speed always resulted in a shorter lag phase, indicating that the strains showed a superior adaptability under higher hydrodynamic conditions. The maximum specific growth rate of M. oxydans, A. faecalis, and S. haemolyticus increased rapidly with the increase of energy dissipation rate till the highest value of 0.386, 0.240, and 0.323 1/h and then decreased as the rotating speed further increased. The phenol biodegradation rate was also dependent on rotating speed, and the trends were consistent with the growth rate variations. A predictive model similar to Haldane model was proposed and was fitted well (R² > 0.913) with bacterial growth under different hydrodynamic conditions. According to the predictive model, the optimum hydrodynamic conditions for the growth of M. oxydans, A. faecalis, and S. haemolyticus were 3.099, 2.197, and 2.289 m²/s³, respectively. The results suggested that non-motile and rod-shaped bacteria were more dependent on hydrodynamic conditions than motile and spherical ones, which could be attributed to the discrepancies in bacterial morphology and motility. The results provide a better understanding on bacterial responses to various hydrodynamic conditions and could be further applied in the bioremediation of contaminated water.

The overapplication of endosulfan on crops has resulted in the widespread contamination of soil. In this study, we examine the potential for bioremediation of the bacteria strain Alcaligenes faecalis JBW4 in degrading endsosulfan in soils. Bacteria were inoculated into sterilized and non-sterilized soils (Argi-Udic Ferrosols and Hapli-Udic Isohumosols) spiked with endosulfan. The results obtained from polymerase chain reaction-denaturing gradient gel electrophoresis indicate that JBW4 colonized Argi-Udic Ferrosols and Hapli-Udic Isohumosols successfully. The degradation efficiencies of α and β isomers of endosulfan by JBW4 were higher in Hapli-Udic Isohumosols than in Argi-Udic Ferrosols, and α and β isomers were degraded by 100.0 and 69.8%, respectively. In addition, detected endosulfan metabolites were either endosulfan ether and endosulfan lactone. Results of the single-cell gel electrophoresis assay showed that the toxicity of endosulfan and its metabolites in Hapli-Udic Isohumosols decreased after 77 days when compared to those in Argi-Udic Ferrosols after degradation by JBW4. Strain JBW4 is an excellent bio-remediator through its ability to degrade endosulfan in contaminated Argi-Udic Ferrosols and Hapli-Udic Isohumosols.

Disposable plastic bags of two different chemical compositions and colors were remediated by the application of novel mesophilic group of bacteria isolated from the banks of sea water, using a 10 week soil burial method. The new strain, LNDR-1, was identified as Alcaligens faecalis by its morphological features and 16S rRNA sequencing. LNDR-1 was able to produce extracellular enzymes such as lipase, CMCase, xylanase, and protease, having PET surface degrading activity. It was found that LNDR-1 had a better decay rate of 15.25 ± 1% and 21.72 ± 2.1% for black and white plastic bags respectively in 10 weeks without prior oxidation as compared to S. marcescens. Polyethylene degradation was confirmed by substantial weight loss, alterations in surface topology, and hydrophobicity index and was found to be directly proportional to the ability to form biofilm on the plastic surface. FTIR results suggest presence of different metabolites in the bags treated with bacterial biofilm in comparison to the control setup inferring various types of metabolic pathways. Present study also reveals the ability of the strain to utilize the used polyethylene bag as the carbon source, without any prior treatment, and as per the literature survey, the working strain is with the capacity to biodegrade plastic at a considerably appreciable rate. This study suggests effectual method for the mechanism of biodegradation of plastic mediated by extracellular enzymes and formation of biofilm.

Crustacean shell waste disposal is considered as biggest problem in seafood processing centers. Incineration and landfilling are the commonest ways of disposal of the waste which causes environmental pollution. Microbial bio-conversion is one of the promising approaches to minimize the wastes by utilizing the same for deriving different value added metabolites. In this perspective, chitinase- and protease-producing bacterial strains were isolated from shrimp culture pond, and the potent isolate was subsequently identified as Alcaligenes faecalis SK10. Fermentative optimization of the production of chitinase (85.42 U/ml), protease (58.57 U/ml), and their catalytic products, viz., N-acetylamino sugar (84 μg/ml) and free amino acids (112 μg/ml), were carried out by utilizing shrimp and crab shell powder as principal substrate. The fermented hydrolysate (FH) was subsequently applied to evaluate its potential to be a candidate fertilizer for the growth of leguminous plant Pisum sativum and Cicer arietinum, and the results were compared with chitin, chitosan, and commercial biofertilizer amended group. The results revealed that FH have paramount potential to improve plants morpho-physiological parameters like stem and root length, chlorophyll, cellular RNA, protein content, and soil physico-chemical parameters like total nitrogen, magnesium, calcium, phosphorus, and potassium significantly (p < 0.05). Moreover, the application of FH also selectively encouraged the growth of free-living nitrogen-fixing bacteria, Rhizobium, phosphate-solubilizing bacteria in the soil by 4.82- and 5.27-, 5.57- and 4.71, and 7.64- and 6.92-fold, respectively, in the rhizosphere of P. sativum and C. arietinum, which collectively is a good sign for an ideal biofertilizer. Co-supplementation of FH with commercial PGPR-biofertilizer significantly influenced the morpho-physiological attributes of plant and physico-chemical and microbial attributes of soil. The study validated proficient and sustainable utilization of fermented hydrolysate of waste crustacean shell as biofertilizer.

A technological system was developed for efficient nitrogen removal from real digester supernatant in a single reactor with shortened aeration to increase the economical aspects of wastewater treatment. The supernatant (600 mg TKN/L, low COD/N ratio of 2.2) was treated in batch reactors with aerobic granules (GSBRs) to test how one, two, or three non-aeration phases and acetate pulse feeding in the cycle affect the morphological and microbial properties of biomass. Introduction of one non-aeration phase in the cycle increased nitrogen removal efficiency by 11 % in comparison with constantly aerated GSBR. The additional non-aeration phases did not diminish the efficiency of ammonia oxidation but did favor nitrification to nitrate. Acetate pulse feeding in the reactor with three non-aeration phases raised the efficiency of nitrogen removal to 77 %; in parallel, the number of denitrifiers possessing nosZ genes and performing denitrification to N₂ increased. Ammonia was oxidized by aerobic and anaerobic ammonia-oxidizing bacteria and heterotrophic nitrifiers (Pseudomonas sp. and Alcaligenes faecalis) that coexisted in granules. Azoarcus sp., Rhizobium sp., and Thauera sp. were core genera of denitrifiers in granules. An increase in the number of non-aeration phases diminished EPS content in the biomass and granule diameters and increased granule density.

Background, aim, and scope Two new high phenol-degrading strains, Micrococcus sp. and Alcaligenes faecalis JH 1013, were isolated. The two isolates could grow aerobically in mineral salts medium containing phenol as a sole carbon source at concentration of 3,000 mg L⁻¹. It was found that the binary mixed culture of the two isolates possessed good potential for phenol removal. Material and methods Phenol biodegradation using the binary mixed culture of the two isolates was studied. The optimal conditions were determined to be temperature 32°C, pH 7.0, inoculum size 10.0%, and agitation rate 150 rpm in the synthetic wastewater. In addition, the kinetics of the cell growth and phenol degradation by the binary mixed culture were also investigated using Haldane model over a wide range of initial phenol concentrations from 20 to 2,400 mg L⁻¹. Results The experimental data indicated that the binary mixed culture had pretty high phenol degradation potential, which could thoroughly degrade the phenol in the synthetic wastewater containing phenol 2,400 mg L⁻¹ within 72 h under aerobic condition. Under the optimal conditions, the phenol concentration was reduced speedily from 1,000 to below 0.28 mg L⁻¹ in the presence of the binary mixed culture, and the phenol degradation rate reached 99.97% after 16 h. It was well below the standard value 0.28 mg L⁻¹ as described by Chinese Environmental Protection Agency. It was clear that the Haldane kinetic model adequately described the dynamic behavior of phenol degradation by the binary mixed culture with kinetic constants of q max = 0.45 h⁻¹, K sq = 64.28 mg L⁻¹, and K iq = 992.79 mg L⁻¹. The phenol concentration to avoid substrate inhibition had been inferred theoretically to be 252.62 mg L⁻¹. Conclusions Phenol, as the only carbon source, could be degraded by the binary mixed culture at high initial phenol concentrations. Phenol exhibited inhibitory behavior, and the growth kinetics of the binary mixed culture could be correlated well by the simple Haldane's inhibitory model. The kinetics parameters were invariably required for the design and simulation of batch and continuous bioreactor treating phenolic wastewaters.

Understanding the interaction between microorganisms and fluid dynamics is important for aquatic ecosystems, though only sporadic attention has been focused on this topic in the past. In this study, particular attention was paid to the phenol-degrading bacterial strains Microbacterium oxydans LY1 and Alcaligenes faecalis LY2 subjected to controlled fluid flow under laboratory conditions. These two strains were found to be able to degrade phenols over a concentration range from 50 to 500 mg/L under different turbulence conditions ranging from 0 to 250 rpm. The time it took to reach total phenol degradation decreased when the turbulence was increased in both strains, with increasing energy dissipation rates ranging from 0.110 to 6.241 W/kg, corresponding to changes in the bacterial diffusive sublayer thickness (δ) and enhanced oxygen uptake. Moreover, the maximum specific growth rates of the two strains also increased with the enhancement of turbulence. A model integrating growth inhibition and fluid motion was proposed based on the self-inhibition Haldane model by introducing a turbulence parameter, α. The resulting modified Haldane model was designed to include fluid motion as a variable in the quantification of the physiological responses of microorganisms. This modified Haldane model could be considered a useful laboratory reference when modeling procedures for water environment bioremediation. Graphical abstract Cell nutrition uptake cartoon schematic diagram for M. oxydans LY1 under different turbulent condition (50 and 200 rpm).

Municipal solid waste landfills are not only a crucial source of global greenhouse gas emissions; they also produce large amounts of ammonia (NH₃), hydrogen sulfide, and other odorous gases that negatively affect the regional environment. Several types of methane-oxidizing bacteria (MOB) were proved to be effective in mitigating methane emission from landfills. Nevertheless, more MOB species and their technical parameters for best mitigating methane still need to be explored. In landfills, methane is simultaneously generated with ammonia, which may impede the CH₄ bio-oxidizing process of MOB. However, very limited studies examined the enhancement of methane reduction by introducing ammonia-oxidizing bacteria (AOB) in landfills. In this study, two enriched MOB cultures were gained from a typical municipal solid waste landfill, and then were cultured with three strains of ammonia-oxidizing bacteria (AOB). The MOB enrichment culture used in this work includes Methylocaldum, Methylocystaceae, and Methyloversatilis, with a methane oxidation capacity of 43.6–65.0%, and the AOB includes Candida ethanolica, Bacillus cereus, and Alcaligenes faecalis. The effects on the emission reduction of both NH₃ and CH₄ were measured using self-made landfill-simulating equipment, as MOB, AOB, and a MOB–AOB mixture were added to the soil cover of the simulation equipment. The concentrations of CH₄ and NH₃ in the MOB–AOB mixture group decreased sharply, and the CH₄ and NH₃ concentration was 76.4% and 83.7% of the control group level. We also found that addition of AOB can help MOB oxidize CH₄ and improve the emission reduction effect.

Farmland soil sprayed with organophosphorus pesticides (OPs) annually was investigated for the identification and characterization of OP-degrading microorganisms. Six bacterial strains were identified, including Brevundimonas faecalis MA-B12 and Alcaligenes faecalis subsp. parafaecalis MA-B13 for methamidophos degradation, Citrobacter freundii TF-B21 and Ochrobactrum intermedium TF-B23 for trichlorfon degradation, Ochrobactrum intermedium DV-B31 for dichlorvos degradation, and Bacillus cereus for dimethoate degradation. The optimal biodegradation conditions for OPs were obtained at pH 7.0 and incubation temperature ranging from 28 to 37 °C. In an 8-day batch test, biodegradation of the four OPs all followed first-order kinetics, with biodegradation rates ranging from 58.08 to 96.42%. Functional genes responsible for OPs degradation were obtained, including ophB, ampA, opdE, opd, opdA, and mpd. As these strains were indigenous strains isolated from farmland soils, they can be potentially used as bacterial consortium for the bioremediation of mixed OP-contaminated soils. A time-course genotoxicity assessment of the degradation products was done by a bacterial whole-cell bioreporter, revealing that biodegradation of trichlorfon, dichlorvos, and dimethoate resulted a decreased genotoxicity within 5 days, which, however, significantly increased on day 8. The result demonstrated that more toxic products may be produced during the biodegradation processes of OPs, and more attention should be put not only on the pesticides themselves, but also on the toxic effects of their degradation products. To the best of our knowledge, this is for the first time that the genotoxicity of OP degradation products was evaluated by the bioreporter assay, broadening our understanding on the genotoxic risks of OPs during biodegradation process. Graphical Abstract