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Extracellular polysaccharides (EPS) of microbial origin are polymers with great potential for research and industrial applications. In this study, a sulphated EPS from Alcaligenes faecalis, previously isolated from Mauritius seawater, was investigated for its antioxidant potential using DPPH (1,1-diphenyl-2-picrylhydrazyl) and ferric reducing capacity assays. The EPS was then further tested for cytotoxicity against five different cell lines namely HepG2, A549, CaSki, HeLa and C33A by incubating them with different concentrations of EPS before assessing cell viability using the MTT assay. In the absence of significant cytotoxic activity, light microscopic observations as well as immunoflurorescent staining were also used to observe any EPS-induced effects on the cells. Finally, the average molecular weight of the polysaccharide was determined by Size-Exclusion Chromatography. The results indicated that the EPS, a 55 KDa polymer, had low ferric reducing capacity but showed up to 70.5% DPPH scavenging activity at the highest EPS concentration (1 mg/ml). In terms of cytotoxicity, HepG2 was the most susceptible among the cell lines, followed by A549, with IC50 values of 128.2 µg/ml and 654.4 µg/ml respectively. Although CaSki, HeLa and C33A were more resistant, microscopic observations showed that the EPS did exert some inhibitory effects on their growth, with C33A showing higher inhibition probably due to the absence of viral proteins as was the case for CaSki and HeLa. These results not only suggest that EPS from A. faecalis have the potential to be considered as antioxidant and cytotoxic compounds but also that they can be further studied for their biotechnological value.

Curdlan is an exopolysaccharide, specifically a homopolysaccharide, with a high molecular weight that is made up entirely of monomeric glucose molecules connected by β-1,3-glycosidic bonds. Curdlan was first isolated in 1962 by Harada and his colleagues from Alcaligenes faecalis var myxogenes 10C3. Microbial synthesis of this curdlan is mainly associated with soil bacteria. Preliminary screening of curdlan-producing microorganisms is done on aniline blue media. The aniline blue positive microorganisms are subjected to submerged fermentation for the production of curdlan. To improve the yield of curdlan produced, various optimization techniques are employed such as Plackett–Burman, response surface methodology, and others. Curdlan can be characterized by its morphology, gel strength, its infrared, and magnetic resonances among many other characteristics. Due to its distinctive physicochemical and rheological properties, it has gained immense popularity in the food, biomedical, and pharmaceutical sectors. However, curdlan’s functionality can be improved by chemically modifying curdlan to obtain grafted curdlan, hydrogels, and nanocomposites which are discussed in detail herewith. Curdlan was authorized to be used in the food industry by the United States Food and Drug Administration in 1996 and also in 1989 in Taiwan, Japan, and Korea. Over the years, many patents using curdlan have also been filed from different parts of the world. This review provides information about its structure, biosynthesis, production strategies, optimization, characterization, applications, and patents. Graphic abstract

Acrylates/acrylic-containing chemicals are components of paints. During industrial production and applications, the acrylates and acrylic-containing compounds could contaminate/accumulate in water bodies and soil systems, hence the need for bioremediation. This study aimed to investigate the in vitro biodegradation of acrylic based paint; using an indigenous bacterial isolate namely; Alcaligenes faecalis and optimization of its activity in shake cultures. The bacterial isolate; A. faecalis (2 % v/v) was able to grow and effectively degrade 68 % of acrylic paints (1 %)-mended mineral salt medium after 14 d of incubation. The rate of biodegradation was significantly (p < 0.05) increased with increasing the medium concentration, inoculum size, agitation speed and nitrogen sources. The most significant biodegradation efficiencies were obtained at a pH of 7.2, temperature of 37 °C, an agitation speed of 200 rpm, an inoculum concentration of 10 %, paint concentration of 2 %; when yeast extract (10 %) was used as a major nitrogen source. Accordingly, this work provides baseline data for optimum biodegradation of acrylate by A. faecalis, and thus could be possibly exploited as an effective bioremediation agent for acrylic paint polluted sites.

A new heterotrophic nitrifying bacterium was isolated from the compost of swine manure and rice husk and identified as Alcaligenes faecalis SDU20. Strain SDU20 had heterotrophic nitrification potential and could remove 99.7% of the initial NH4+-N. Nitrogen balance analysis revealed that 15.9 and 12.3% of the NH4+-N were converted into biological nitrogen and nitrate nitrogen, respectively. The remaining 71.44% could be converted into N2 or N2O. Single-factor experiments showed that the optimal conditions for ammonium removal were the carbon source of sodium succinate, C/N ratio 10, initial pH 8.0, and temperature 30 °C. Nitrification genes were determined to be upregulated when sodium succinate was used as the carbon source analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Strain SDU20 could tolerate 4% salinity and show resistance to some heavy metal ions. Strain SDU20 removed 72.6% high concentrated NH4+-N of 2000 mg/L within 216 h. In a batch experiment, the highest NH4+-N removal efficiency of 98.7% and COD removal efficiency of 93.7% were obtained in the treatment of unsterilized swine wastewater. Strain SDU20 is promising in high-ammonium wastewater treatment.

Chemical extraction of chitin is very hazardous and costly which can be overwhelmed by microbial bioprocessing. In this study, potent protease and lactic acid-producing bacteria were screened and identified as Alcaligens faecalis S3 and Bacillus coagulans L2, respectively. Productions of protease and lactic acid by the respective bacterial strains were optimized. The shell of Litopenaeus vannamei was sequentially treated with the partially purified protease and lactic acid and the treatment conditions were optimized for betterment of chitin yield. Spectral characterization by SEM-EDS, IR, XRD, NMR, XPS and thermal characterization by TG and DTG analysis of the extracted chitin was made and compared with commercial one. It was revealed that both the chitin have similar characteristics. Therefore, it can be articulated that chitin can be extracted from crustacean shells in pure form by microbial bioprocessing which will be a good catch for biorefinary industries for chitin extraction through greener route.

Coke oven sector emanates phenol and cyanide as the eminent virulent compounds due to abrupt industrialization which is detrimental in aqueous state, and its severity is increased on simultaneous coexistence even at low concentrations that eventually causes extensive damage to the peripheral ecosystem. The efficacy of isolated mixed bacterial culture comprising of Alcaligenes faecalis JF339228 and Klebsiella oxytoca KF303807 in wastewater treatment was investigated following a batch study. The impact of initial concentration of phenol (100–1500 mg L−1) and cyanide (10–150 mg L−1) on the growth and treatment by the mixed microbial cultures were evaluated over a time period of 72 h. The biodegradation mechanism was explained by Monod, Haldane, Aiba and Edward kinetic models. The maximum specific growth rate was reported to be 0.096 h−1 and 0.126 h−1 for phenol and cyanide respectively. The substrate inhibitory effect became eminent after a concentration of 450 mg L−1 for phenol and 45 mg L−1 for cyanide. Based on the lower sum of squared error (SSE) values, Haldane model for phenol and Edward model for cyanide was found to be favourable for substrate inhibition kinetics. The fate of the secondary intermediates produced after microbial degradation was assessed by phytotoxicity studies using Vigna radiata. The interactive binding of the pernicious pollutants and resultant biodegraded compounds with the DNA (herring sperm DNA) was examined following spectrofluorometric and spectrophotometric anatomization. Toxicity studies revealed that biological treatment was viable for eco benign disposal and results also depicted that both the strains have potential in remediation of phenol and cyanide from coke oven wastewater.

Chlorpyrifos (Chlp), one of the major organophosphates is extensively used in agriculture to control pests. With a half-life of 7–120 d, it may persist for up to one year in soil depending on the s...

BackgroundDue to the multitude industrial applications of ligninolytic enzymes, their demands are increasing. Partial purification and intensive characterization of contemporary highly acidic laccase enzyme produced by an Egyptian local isolate designatedAlcaligenes faecalisNYSO were studied in the present investigation.ResultsAlcaligenes faecalisNYSO laccase has been partially purified and intensively biochemically characterized. It was noticed that 40–60% ammonium sulfate saturation showed maximum activity. A protein band with an apparent molecular mass of ~ 50 kDa related to NYSO laccase was identified through SDS-PAGE and zymography. The partially purified enzyme exhibited maximum activity at 55 °C and pH suboptimal (2.5–5.0). Remarkable activation for enzyme activity was recognized after 10-min exposure to temperatures (T) 50, 60, and 70 °C; time elongation caused inactivation, where ~ 50% of activity was lost after a 7-h exposure to 60 °C.Some metal ions Cu2+, Zn2+, Co2+,Ni2+, Mn2+, Cd2+, Cr2+, and Mg2+caused strong stimulation for enzyme activity, but Fe2+and Hg2+reduced the activity. One millimolar of chelating agents [ethylenediamine tetraacetic acid (EDTA), sodium citrate, and sodium oxalate] caused strong activation for enzyme activity. Sodium dodecyl sulfate (SDS), cysteine-HCl, dithiothreitol (DTT), β-mercaptoethanol, thioglycolic acid, and sodium azide caused strong inhibition for NYSO laccase activity even at low concentration. One millimolar of urea, imidazole, kojic acid, phenylmethylsulfonyl fluoride (PMSF), H2O2, and Triton X-100 caused activation. The partially purified NYSO laccase had decolorization activity towards different dyes such as congo red, crystal violet, methylene blue, fast green, basic fuchsin, bromophenol blue, malachite green, bromocresol purple eriochrome black T, and Coomassie Brilliant Blue R-250 with various degree of degradation. Also, it had a vast range of substrate specificity including lignin, but with high affinity towards p-anisidine.ConclusionThe promising properties of the newly studied laccase enzyme fromAlcaligenes faecalisNYSO strain would support several industries such as textile, food, and paper and open the possibility for commercial use in water treatment. It will also open the door to new applications due to its ligninolytic properties in the near future.

Twelve new analogues of gabapentin (GBP) derived hydrazide-hydrazone scaffolds were produced by using various electronically and structurally divergent aromatic aldehydes. All the hydrazones were obtained in moderate to good yields (66–82%) by heating the GBP hydrazide with respective aldehydes to a temperature of 45–65 °C for 4–7 h. Further, the compounds were explored for their antimicrobial activity on three different Gram positive (Micrococcus luteus, Streptococcus mutans, Enterococcus faecalis) and Gram negative bacterial strains (Salmonella enterica, Alcaligenes faecalis, Pseudomonas aeruginosa). The antibacterial results obtained were found to be good against Gram positive bacteria when compared to Gram negative bacteria. Moreover, the compounds were also screened for antioxidant activity at four different concentrations using the DPPH method and the results showed that some of the compounds were moderately active.

Microbial immobilization is considered as one of the effective denitrification techniques in the treatment of high load wastewater. In this study, the immobilized cells consisting of polyvinyl alco...

The continuous development of multidrug resistance pathogens with limited therapeutic options has become a great problem globally that impose sever health hazards. Accordingly, searching for of new antimicrobials became an urgent demand and great challenge. Soil significantly have been associated with several species that are antibiotic producers. In this study, combination of conventional screening methods with Liquid chromatography- Mass spectroscopy (LC/MS) and metagenomic nanopore sequence analysis have been conducted for the deciphering the active metabolites produced by soil isolate(s). Preliminary soil screening resulted in a Gram-negative isolate identified via 16S ribosomal RNA as Alcaligenes faecalis isolate MZ921504 with promising antimicrobial activities against wide range of MDR gram-positive and gram-negative pathogens. The LC/MS analysis of the metabolites of A. faecalis isolate MZ921504 confirmed the presence of ectoine, bacillibactin, quinolobactin and burkholderic acid. Metagenomics sequence analysis of the soil sample (NCBI GenBank accession PRJNA771993) revealed the presence of conserved biosynthetic gene clusters of ectoine, bacteriocin, bacillibactin, quinolobactin, terpene and burkholderic acid of A. faecalis. In conclusion, A. faecalis isolate MZ921504 is a promising source for antimicrobial metabolites. LC/MS spectral analysis and third generation sequencing tools followed by secondary metabolite gene clusters analysis are useful methods to predict the nature of the antimicrobial metabolites.

Alcaligenes faecalis is a heterotrophic nitrifying bacterium that oxidizes ammonia and generates nitrite and nitrate. When A. faecalis was cultivated in a medium containing pyruvate and ammonia as the sole carbon and nitrogen sources, respectively, high concentrations of nitrite accumulated in the medium whose carbon/nitrogen (C/N) ratio was lower than 10 during the exponential growth phase, while the accumulation was not observed in the medium whose C/N ratio was higher than 15. Comparative transcriptome analysis was performed using nitrifying and non-nitrifying cells of A. faecalis cultivated in media whose C/N ratios were 5 and 20, respectively, to evaluate the fluctuations of gene expression during induction of heterotrophic nitrification. Expression levels of genes involved in primary metabolism did not change significantly in the cells at the exponential growth phase under both conditions. We observed a significant increase in the expression levels of four gene clusters: pod cluster containing the gene encoding pyruvic oxime dioxygenase (POD), podh cluster containing the gene encoding a POD homolog (PODh), suf cluster involved in an iron-sulfur cluster biogenesis, and dnf cluster involved in a novel hydroxylamine oxidation pathway in the nitrifying cells. Our results provide valuable insight into the biochemical mechanism of heterotrophic nitrification.

Vanillin is the major component which is responsible for flavor and aroma of vanilla extract and is produced by 3 ways: natural extraction from vanilla plant, chemical synthesis and from microbial transformation. Current research was aimed to study bacterial production of vanillin from native natural sources including sewage and soil from industrial areas. The main objective was vanillin bio-production by isolating bacteria from these native sources. Also to adapt methodologies to improve vanillin production by optimized fermentation media and growth conditions. 47 soil and 13 sewage samples were collected from different industrial regions of Lahore, Gujranwala, Faisalabad and Kasur. 67.7% bacterial isolates produced vanillin and 32.3% were non-producers. From these 279 producers, 4 bacterial isolates selected as significant producers were; A3, A4, A7 and A10. These isolates were identified by ribotyping as A3 Pseudomonas fluorescence (KF408302), A4 Enterococcus faecium (KT356807), A7 Alcaligenes faecalis (MW422815) and A10 Bacillus subtilis (KT962919). Vanillin producers were further tested for improved production of vanillin and were grown in different fermentation media under optimized growth conditions for enhanced production of vanillin. The fermentation media (FM) were; clove oil based, rice bran waste (residues oil) based, wheat bran based and modified isoeugenol based. In FM5, FM21, FM22, FM23, FM24, FM30, FM31, FM32, FM34, FM35, FM36, and FM37, the selected 4 bacterial strains produced significant amounts of vanillin. A10 B. subtilis produced maximum amount of vanillin. This strain produced 17.3 g/L vanillin in FM36. Cost of this fermentation medium 36 was 131.5 rupees/L. This fermentation medium was modified isoeugenol based medium with 1% of isoeugenol and 2.5 g/L soybean meal. ech gene was amplified in A3 P. fluorescence using ech specific primers. As vanillin use as flavor has increased tremendously, the bioproduction of vanillin must be focused. Resumo A vanilina é o principal componente responsável pelo sabor e aroma do extrato de baunilha e é produzida de três formas: extração natural da planta da baunilha, síntese química e transformação microbiana. A pesquisa atual teve como objetivo estudar a produção bacteriana de vanilina a partir de fontes naturais nativas, incluindo esgoto e solo de áreas industriais. O objetivo principal era a bioprodução de vanilina por meio do isolamento de bactérias dessas fontes nativas. Também para adaptar metodologias para melhorar a produção de vanilina por meio de fermentação otimizada e condições de crescimento. Foram coletadas 47 amostras de solo e 13 de esgoto de diferentes regiões industriais de Lahore, Gujranwala, Faisalabad e Kasur; 67,7% dos isolados bacterianos produziram vanilina e 32,3% eram não produtores. Desses 279 produtores, 4 isolados bacterianos selecionados como produtores significativos foram: A3, A4, A7 e A10. Esses isolados foram identificados por ribotipagem como fluorescência A3 Pseudomonas (KF408302), A4 Enterococcus faecium (KT356807), A7 Alcaligenes faecalis (MW422815) e A10 Bacillus subtilis (KT962919). Os produtores de vanilina foram posteriormente testados para produção aprimorada de vanilina e foram cultivados em diferentes meios de fermentação sob condições de crescimento otimizadas para produção aprimorada de vanilina. Os meios de fermentação (FM) foram: à base de óleo de cravo, à base de resíduos de farelo de arroz (resíduos de óleo), à base de farelo de trigo e à base de isoeugenol modificado. Em FM5, FM21, FM22, FM23, FM24, FM30, FM31, FM32, FM34, FM35, FM36 e FM37, as 4 cepas bacterianas selecionadas produziram quantidades significativas de vanilina. A10 B. subtilis produziu quantidade máxima de vanilina. Essa cepa produziu 17,3 g / L de vanilina em FM36. O custo desse meio de fermentação 36 foi de 131,5 rúpias / L. Esse meio de fermentação foi um meio à base de isoeugenol modificado com 1% de isoeugenol e 2,5 g / L de farelo de soja. O gene ech foi amplificado em A3 P. fluorescence usando primers específicos para ech. Como o uso da vanilina como sabor aumentou tremendamente, a bioprodução da vanilina deve ser focada.

Glucan (from Alcaligenes faecalis) is a polymer composed of β-1,3-linked glucose residues, and it has been addressed in different medical fields, namely in nanotechnology, as a vaccine or a drug delivery system. However, due to their small size, nanomaterials may present new risks and uncertainties. Thus, this work aims to describe the production of glucan nanoparticles (NPs) with two different sizes, and to evaluate the influence of the NPs size on immunotoxicity. Results showed that, immediately after production, glucan NPs presented average sizes of 129.7 ± 2.5 and 355.4 ± 41.0 nm. Glucan NPs of 130 nm presented greater ability to decrease human peripheral blood mononuclear cells and macrophage viability and to induce reactive oxygen species production than glucan NPs of 355 nm. Both NP sizes caused hemolysis and induced a higher metabolic activity in lymphocytes, although the concentration required to observe such effect was lower for the 130 nm glucan NPs. Regarding pro-inflammatory cytokines, only the larger glucan NPs (355 nm) were able to induce the secretion of IL-6 and TNF-α, probably due to their recognition by dectin-1. This higher immunomodulatory effect of the larger NPs was also observed in its ability to stimulate the production of nitric oxide (NO) and IL-1β. On the contrary, a small amount of Glu 130 NPs inhibited NO production. In conclusion, on the safe-by-design of glucan NPs, the size of the particles should be an important critical quality attribute to guarantee the safety and effectiveness of the nanomedicine.

Cells of amidase containing bacteria of Rhodococcus erythropolis 4-1 and Alcaligenes faecalis 2 were immobilized using carriers such as barium alginate, agarose, chitosan and κ-carrageenan. The aim of the work was to study the effect of bacterial cell immobilization methods on the operational stability of a bio-catalyst. It has been determined that the best carrier for the stable operation of the biocatalyst was aga-rose. The highest amount of acrylic acid was obtained during multi-cycle transformation of acrylamide by immobilized A. faecalis 2 cells.

Nitrite reductases are enzymes that aid in the denitrification process by catalyzing the reduction of nitrite to nitric oxide gas. Since this reaction is the first committed step that involves gas formation, it is regarded to be a vital step for denitrification. However, the mechanism of copper-containing nitrite reductase is still under debate due to the discrepancy between the theoretical and experimental data, especially in terms of the roles of secondary shell residues Asp98 and His255 and the electron transfer mechanism between the two copper sites. Herein, we revisited the nitrite reduction mechanism of A. faecalis copper nitrite reductase using QM(B3LYP)/MM-based metadynamics. It is found that the intramolecular electron transfer from T1-Cu to T2-Cu occurs via an asynchronous proton-coupled electron transfer (PCET) mechanism, with electron transfer (ET) preceding proton transfer (PT). In particular, we found that the ET process is driven by the conformation conversion of Asp98 from the gatekeeper to the proximal one, which is much more energy-demanding than the PCET itself. These results highlight that the inclusion of an electron donor is vital to investigate electron-transfer related processes such as PCET.

Biological ammonium removal from wastewater requires coupling of nitrification and denitrification processes in respective aerobic and anaerobic conditions. This difference in environmental requirements pose a big challenge in the design of systems intended to effect both nitrification and denitrification processes. Alcaligenes faecalis strain No. 4, however, has both heterotrophic nitrification and aerobic denitrification abilities in aerobic conditions, eliminating the need to provide anaerobic conditions for denitrification. Batch and continuous experiments in a mixed culture of A. faecalis No. 4 and activated sludge were performed to examine ammonium removal and microbial stability of No. 4 in aerobic reactors. At an inflow ammonium load of 500 mg L-1 d-1 in continuous experiment, the ammonium removal rate (21 mg L-1 h-1), under No. 4, was approximately 2 times higher than that of the control (i.e., without No. 4), and the denitrification ratio was approximately 66%. The proportion of intracellular nitrogen converted from removed ammonium in the continuous mixed culture was reduced, compared to control batch and continuous cultures. These results demonstrated stable growth as well as the heterotrophic nitrification-aerobic denitrification abilities of No. 4 in activated sludge systems.

The temperature dependence of the rate of acrylamide biodegradation by silt microorganisms of small rivers in the Perm krai is studied in the antropogenically polluted Danilikha River, flowing in the territory of Perm city, and the Syuz’va River’s relatively clear tributary in Nytvenskii district. The rate of acrylamide biodegradation increases after introducing into river silt the biomass of bacteria of strains Alcaligenes faecalis 2 and Acinetobacter guillouiae 11h, selected toward an increase in amidase activity. It is shown that, at the ambient temperature of 30°C, the complete degradation of 100 mM acrylamide solution by silt microbiocenosis from the Danilikha River and a tributary of the Syuz’va River has taken place by the 21st and 28th day, respectively, while at 5 and 16–20°C, acrylamide concentration has decreased only slightly even by the 63rd day. The introduction of the biomass of preselected bacteria considerably reduces the time required for complete degradation of acrylamide. At temperature 5°C, acrylamide utilization can take place only at inoculation of silts by the biomass of amidase-containing microorganisms. A mathematical model of acrylamide biodegradation in silt suspensions of small rivers is given; kinetic curves of changes in its concentration are presented, and temperature dependences of biodegradation rates are obtained for different variants of the process.

Flonicamid (N-cyanomethyl-4-trifluoromethylnicotinamide, FLO), a novel selective systemic pyridinecarboxamide insecticide, effectively controls hemipterous pests. However, microbial degradation of flonicamid, along with the enzymatic mechanism, has not been studied. Here, bacterial isolate PG13, which converts flonicamid into 4-(trifluoromethyl)nicotinol glycine (TFNG) and N-(4-trifluoromethylnicotinoyl)glycinamide (TFNG-AM), was isolated and identified as Alcaligenes faecalis CGMCC 17553. The genome of CGMCC 17553 contained five nitrilases but no nitrile hydratase, and recombinant Escherichia coli strains harboring CGMCC 17553 nitrilase gene nitA or nitD acquired the ability to degrade flonicamid. Purified NitA catalyzed flonicamid into both TFNG and TFNG-AM, indicating dual functionality, while NitD could only produce TFNG-AM. Three-dimensional homology modeling revealed that aromatic amino acid residues in the catalytic pocket affected nitrilase activity. These findings further our understanding of the enzymatic mechanism of flonicamid metabolism in the environment and may help develop a potential bioremediation agent for the elimination of flonicamid contamination.

N2O production from NH2OH oxidation involved in a heterotrophic nitrifier Alcaligenes faecalis strain NR was studied. 15N-labeling experiments showed that biological NH2OH consumption by strain NR played a dominant role in N2O production, although chemical reaction between NH2OH and O2 indeed existed. Hydroxylamine oxidoreductase (HAO) from strain NR was partially purified by (NH4)2SO4 fractionation and DEAE Cartridge chromatography. The maximum activity of HAO was 9.60 mU with a specific activity of 92.04 mU/(mg protein) when K3Fe(CN)6 was used as an electron acceptor. The addition of Ca2+ promoted the HAO activity, while the presence of Mn2+ inhibited the enzyme activity. The optimal temperature and pH for HAO activity were 30 °C and 8. Analysis of enzyme-catalyzed products demonstrated that NH2OH oxidation catalyzed by HAO from strain NR played significant role in the production of N2O.

Native 3-hydroxybutyrate dehydrogenase from Alcaligenes faecalis can catalyze the reversible reduction of acetoacetate, a four carbon chain oxo acid. This enzyme has been engineered to enable the reduction of levulinic acid, with one carbon longer than acetoacetate. In this study, the native and engineered enzymes were subjected to the catalysis of oxo acids with a carbon chain length of 3 to 8, in order to examine the capability of the enzyme to work on various platform chemicals. The engineered enzyme could reduce the C7 and C8 oxo acids whereas the wild-type had no activity on these substrates. Docking simulation has indicated Tyr155 and Ser142 are key residues for the catalysis. In addition, stable hydrogen bond formation between Gln196 and the substrates affects the turnover rate. Mutation sites in the engineered enzyme were focused on creating larger active site volume for substrates with extended chain lengths. Both qualitative and quantitative structural basis for the enzyme substrate specificity on alpha, beta, gamma and omega hydroxy acids could be elucidated.

One hundred and fifty six native bacterial strains with different morphological characters were isolated from water and soil samples collected from textile wastewater effluent sites, Sri Lanka. Three isolated bacterial strains were more effective on decolorization of CI Direct Blue 201 textile dye and 16s rRNA analysis reveals that the bacterial strains were Alcaligenes faecalis (MK166784), Micrococcus luteus (MK166783) and Staphylococcus warneri (MK256311). A. faecalis, M. luteus and S. warneri showed complete decolorization of CI Direct Blue 201 textile dye within 60, 64, and 72 h of incubation time respectively under the static conditions at 28 oC. Decolorization was effective at a temperature range from 24 oC to 40 oC and pH range from 7 to 9. The presence of tryptone, peptone or yeast in the Mineral Salt Medium enhanced the decolorization of the dye. Phytotoxicity assay based on the seed germination percentages of Oryza sativa and Vigna radiate showed that the detoxification of CI Direct Blue 201 textile dye after the bacterial treatment was effective signifying the potential applicability of the A. faecalis, M. luteus and S. warneri to develop a green application to treat textile wastewater.

The biocatalytic synthesis of acrylic acid from acrylamide by the Rhodococcus erythropolis 4-1 and Alcaligenes faecalis 2 strains with amidase activity is studied. The optimum pH values are 6–7 for R. erythropolis 4-1 and 7–7.5 for A. faecalis 2, while the optimum temperature is 20–50°С for both strains. The optimum acrylamide concentration is 150 mM for R. erythropolis 4-1 and 250 mM for A. faecalis 2. The synthesis of acrylic acid with fractional additions of a substrate catalyzed by the biomass of A. faecalis 2 is more effective than using R. erythropolis 4-1. The biocatalyst is best stored at −20°C. The amidase activity of A. faecalis 2 cells immobilized on chitosan activated with glutaraldehyde and non-activated chitosan did not decline during the storage of either wet or dried granules.

The possibility of using amides of halogen-substituted acetic acids as acyl donors in penicillin acylase-catalyzed reactions has been investigated, and the ability of this group of compounds to inactivate enzymes in the course of the catalytic conversion has been established. The strongest inactivating effect was demonstrated by iodoacetamide and bromoacetamide. However, the negative contribution of this side activity can be minimized by decreasing the temperature, when the rate of acyl donor conversion by penicillin acylases is still high enough, but the impact of enzyme inactivation becomes less significant. The catalytic activity of penicillin acylase from Alcaligenes faecalis in the conversion of 2-haloacetamides was significantly (5-8 times) higher than that of penicillin acylase from Escherichia coli.

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.

Bacterial species for metabolizing dye molecules were isolated from dye rich water bodies. The best microbial species for such an application was selected amongst the isolated bacterial populations by conducting methylene blue (MB) batch degradation studies with the bacterial strains using NaCl-yeast as a nutrient medium. The most suitable bacterial species was Alcaligenes faecalis (A. faecalis) according to 16S rDNA sequencing. Process parameters were optimized and under the optimum conditions (e.g., inoculum size of 3 mL, temperature of 30 °C, 150 ppm, and time of 5 days), 96.2% of MB was removed. Furthermore, the effectiveness for the separation of MB combining bio-film with biochar was measured by a bio-sorption method in a packed bed bioreactor (PBBR) in which microbes was immobilized. The maximum MB removal efficiencies, when tested with 50 ppm dye using batch reactors containing free A. faecalis cells and the same cells immobilized on the biochar surface, were found to be 81.5% and 89.1%, respectively. The PBBR operated in continuous recycle mode at high dye concentration of 500 ppm provided 87.0% removal of MB through second-order kinetics over 10 days. The % removal was found in the order of PBBR>Immobilized batch>Free cell. The standalone biochar batch adsorption of MB can be described well by the pseudo-second order kinetics (R2 ≥ 0.978), indicating the major contribution of electron exchange-based valence forces in the sorption of MB onto the biochar surface. The Langmuir isotherm suggested a maximum monolayer adsorption capacity of 4.69 mg g−1 at 40 °C which was very close to experimentally calculated value (4.97 mg g−1). Moreover, the Casuarina seed biochar was reusable 5 times.

Alcaligenes spp., including A. faecalis, is a gram-negative facultative bacterium uniquely residing inside the Peyer’s patches. We previously showed that A. faecalis-derived lipopolysaccharides (Alcaligenes LPS) acts as a weak agonist of toll-like receptor 4 to activate dendritic cells and shows adjuvant activity by enhancing IgG and Th17 responses to systemic vaccination. Here, we examined the efficacy of Alcaligenes LPS as a nasal vaccine adjuvant. Nasal immunization with ovalbumin (OVA) plus Alcaligenes LPS induced follicular T helper cells and germinal center formation in the nasopharynx-associated lymphoid tissue (NALT) and cervical lymph nodes (CLNs), and consequently enhanced OVA-specific IgA and IgG responses in the respiratory tract and serum. In addition, nasal immunization with OVA plus Alcaligenes LPS induced OVA-specific T cells producing IL-17 and/or IL-10, whereas nasal immunization with OVA plus cholera toxin (CT) induced OVA-specific T cells producing IFN-γ and IL-17, which are recognized as pathogenic type of Th17 cells. In addition, CT, but not Alcaligenes LPS, promoted the production of TNF-α and IL-5 by T cells. Nasal immunization with OVA plus CT, but not Alcaligenes LPS, led to increased numbers of neutrophils and eosinophils in the nasal cavity. Together, these findings indicate that the benign nature of Alcaligenes LPS is an effective nasal vaccine adjuvant that induces antigen-specific mucosal and systemic immune responses without activation of inflammatory cascade after nasal administration.

β-glucan consumption is known for its beneficial health effects, but the mode of action is unclear. While humans and mice lack the required enzymes to digest β-glucans, certain intestinal microbes can digest β-glucans, triggering gut microbial changes. Curdlan, a particulate β-glucan isolated from Alcaligenes faecalis, is used as a food additive. In this study we determined the effect of curdlan intake in mice on the intestinal microbiota and dextran sodium sulfate (DSS)-induced intestinal inflammation. The effect of curdlan on the human intestinal microbiota was assessed using i-screen, an assay for studying anaerobic microbial interactions. Mice received oral gavage with vehicle or curdlan for 14 days followed by DSS for 7 days. The curdlan-fed group showed reduced weight loss and colonic inflammation compared to the vehicle-fed group. Curdlan intake did not induce general microbiota community changes, although a specific Bifidobacterium, closely related to Bifidobacterium choerinum, was observed to be 10- to 100-fold more prevalent in the curdlan-fed group under control and colitis conditions, respectively. When tested in i-screen, curdlan induced a global change in the microbial composition of the healthy intestinal microbiota from a human. Overall, these results suggest that dietary curdlan induces microbiota changes that could reduce intestinal inflammation.

High lead (Pb) concentration in soils is becoming a severe threat to human health. It also deteriorates plants, growth, yield and quality of food. Although the use of plant growth-promoting rhizobacteria (PGPR), biochar and compost can be effective environment-friendly amendments for decreasing Pb stress in crop plants, the impacts of their simultaneous co-application has not been well documented. Thus current study was carried, was conducted to investigate the role of rhizobacteria and compost mixed biochar (CB) under Pb stress on selected soil properties and agronomic parameters in mint (Mentha piperita L.) plants. To this end, six treatments were studied: Alcaligenes faecalis, Bacillus amyloliquefaciens, CB, PGPR1 + CB, PGPR2 + CB and control. Results showed that the application A. faecalis + CB significantly decreased soil pH and EC over control. However, OM, nitrogen, phosphorus and potassium concentration were significantly improved in the soil where A. faecalis + CB was applied over control. The A. faecalis + CB treatment significantly improved mint plant root dry weight (58%), leaves dry weight (32%), chlorophyll (37%), and N (46%), P (39%) and K (63%) leave concentration, while also decreasing the leaves Pb uptake by 13.5% when compared to the unamended control. In conclusion, A. faecalis + CB has a greater potential to improve overall soil quality, fertility and mint plant productivity under high Pb soil concentration compared to the sole application of CB and A. faecalis.

The main objective of this study was to evaluate the ability of both antagonistic bacteria Bacillus amyloliquefaciens (SF14) and Alcaligenes faecalis (ACBC1) used in combination with salicylic acid (SA) to effectively control brown rot disease caused by Monilinia fructigena. Four concentrations of salicylic acid (0.5%, 2%, 3.5%, and 5%) were tested under in vitro and in vivo conditions. Furthermore, the impact of biological treatments on nectarine fruit parameters&rsquo, quality, in particular, weight loss, titratable acidity, and soluble solids content, was evaluated. Regardless of the bacterium, the results indicated that all combined treatments displayed a strong inhibitory effect on the mycelial growth of M. fructigena and disease severity. Interestingly, all SA concentrations significantly improved the biocontrol activity of each antagonist. The mycelial growth inhibition rate ranged from 9.79% to 88.02% with the highest reduction rate recorded for bacterial antagonists in combination with SA at both concentrations of 0.5% and 3.5%. The in vivo results confirmed the in vitro results with a disease severity varying from 0.00% to 51.91%. A significant biocontrol improvement was obtained with both antagonistic bacteria when used in combination with SA at concentrations of 0.5% and 2%. The lowest disease severity observed with ACBC1 compared with SF14 is likely due to a rapid adaptation and increase of antagonistic bacteria population in wounded sites. The impact of all biological treatments revealed moderate significant changes in the fruit quality parameters with weight loss for several treatments. These results suggest that the improved disease control of both antagonistic bacteria was more likely directly linked to both the inhibitory effects of SA on pathogen growth and induced fruit resistance.

High cost is one of the limiting factors in the industrial production of bioflocculant. Simultaneous preparation of bioflocculant from the contaminants in wastewater was considered as a potential approach to reduce the production cost. In this study, caprolactam was verified as sole feedstock for the growth of strain Alcaligenes faecalis subsp. phenolicus ZY-16 in batch experiments. Chemical analysis showed that the as-prepared MBF-16 consisted of heteropolysaccharides (88.3%) and peptides (9.4%). XPS result indicated the plentiful acylamino, hydroxyl and amino groups in MBF-16, which have an indispensable role in amoxicillin flocculation. The flocculation of amoxicillin can be well stimulated by Freundlich isotherm equation, and the Kf was up to 178.6524 for amoxicillin. The kinetic fitting results proved that the flocculation of amoxicillin by MBF-16 was chemisorbed. This contribution may develop a novel technology for the preparation of bacterial flocculants that can consume toxic substrates (caprolactam) and have potential applications in amoxicillin removal.

In the marine environment bacterial-induced metamorphosis of larvae is a widespread cross-kingdom communication phenomenon and critical for the persistence of many marine invertebrates. However, the identities of most inducing bacterial signals and the underlying cellular mechanisms remain enigmatic. Larvae of Hydractinia echinata provide an excellent model for investigating bacteria-stimulated settlement as they transform upon detection of the signal into the colonial adult stage within 24 h. Although H. echinata served as cell biological model system for decades, the influence of bacterial signals on the morphogenic transition remained largely unexplored. Using a bioassay-guided analysis, we first identified that specific bacterial (lyso)phospholipids, naturally present in bacterial biofilms, elicit metamorphosis in Hydractinia larvae in a dose-response matter. In particular, lysophospholipids as single compounds or in combinations at 50 µM concentrations induced metamorphosis in up to 50% of all larvae phospholipid within 48 h. By using fluorescence-labeled bacterial phospholipids, we demonstrated their incorporation into the larval membranes, where interactions with internal signaling cascades could occur. In addition, two structurally distinct exopolysaccharides, the newly identified Rha-Man polysaccharide from Pseudoalteromonas sp. P1-9 and curdlan from Alcaligenes faecalis caused up to 75% of all larvae to transform within 24 h. We also found that combinations of (lyso)phospholipids and curdlan induced the transformation in almost all larvae within 24 h, thereby exceeding the morphogenic activity observed for single compounds and axenic bacterial biofilms. Our results demonstrate that multiple and structurally distinct bacterial-derived metabolites converge to induce high transformation rates of Hydractinia larvae, which might ensure optimal habitat selection despite the general widespread occurrence of both compound classes.Significance StatementBacterial biofilms profoundly influence the recruitment and settlement of marine invertebrates, critical steps for diverse marine processes such as coral reef formation, marine fisheries and the fouling of submerged surfaces. Yet, the complex composition of biofilms often makes it challenging to characterize the individual signals and regulatory mechanisms. Developing tractable model systems to characterize these co-evolved interactions is the key to understand fundamental processes in evolutionary biology. Here, we characterized for the first time two types of bacterial signaling molecules that induce the morphogenic transition and analyzed their abundance and combinatorial activity. This study highlights the crucial role of the converging activity of multiple bacterial signals in development-related cross-kingdom signaling.AreasMajor: Chemical Biology, Microbiology, Developmental Biology

Alcaligenes faecalis is the predominant Gram‐negative bacterium inhabiting gut‐associated lymphoid tissues, Peyer's patches. We previously reported that an A. faecalis lipopolysaccharide (LPS) acted as a weak agonist for Toll‐like receptor 4 (TLR4)/myeloid differentiation factor‐2 (MD‐2) receptor as well as a potent inducer of IgA without excessive inflammation, thus suggesting that A. faecalis LPS might be used as a safe adjuvant. In this study, we characterized the structure of both the lipooligosaccharide (LOS) and LPS from A. faecalis. We synthesized three lipid A molecules with different degrees of acylation by an efficient route involving the simultaneous introduction of 1‐ and 4′‐phosphates. Hexaacylated A. faecalis lipid A showed moderate agonistic activity towards TLR4‐mediated signaling and the ability to elicit a discrete interleukin‐6 release in human cell lines and mice. It was thus found to be the active principle of the LOS/LPS and a promising vaccine adjuvant candidate., A host–microbe chemical ecology study revealed an effective and safe immunomodulator from Alcaligenes faecalis resident in gut‐associated lymphoid tissues, Peyer's patches (see picture). The complete structures of both the lipooligosaccharide and the lipopolysaccharide from A. faecalis were characterized. Furthermore, A. faecalis lipid A molecules were synthesized with varying degrees of acylation and found to be a promising vaccine adjuvant candidate.

Neem (Azadirachta indica [AI]) is a unique and traditional source of antioxidant and antibacterial compounds. The GC-MS studies revealed that phytoextract of Azadirachta indica comprises a large number of phytocompounds that possess the efficacy of inhibiting the biofilm. It was observed that phytocompounds like catechin showed maximum eradication of biofilm along with the degradation of EPS structural components like carbohydrates and proteins compared to quercetin, nimbolide, nimbin, and azardirachtin, and hence, catechin was proved to be the best against dental plaque-forming bacteria. It was also observed that catechin was able to bring about a marked reduction in quorum sensing (QS) both in Alcaligenes faecalis and Pseudomonas gingivalis dental biofilm-forming strains. The extent of such reduction was maximum for catechin (94.56±2.56% in P. gingivalis & 96.56±2.5 in A. faecalis) in comparison to other bioactive compounds. It was further observed that the bioactive compounds possess the ability to quickly pass across the membrane and bring about inhibition in the DNA and RNA content of the sessile cells. This was further validated by microscopic and in silico studies. Thus, this study revealed that catechin obtained from the phytoextract of AI showed a marked ability to inhibit the dental biofilm and can be used as a natural drug-like compound in treating biofilm-associated chronic infections.

Lymphoid-tissue–resident commensal bacteria (LRCs), including Alcaligenes faecalis, are present in intestinal lymphoid tissue including the Peyer’s patches (PPs) of mammals and modulate the host immune system. Although LRCs can colonize within dendritic cells (DCs), the mechanisms through which LRCs persist in DCs and the symbiotic relationships between LRCs and DCs remain to be investigated. Here, we show an intracellular symbiotic system in which the LRC Alcaligenes creates a unique energy shift in DCs. Whereas DCs showed low mitochondrial respiration when they were co-cultured with Escherichia coli, DCs carrying A. faecalis maintained increased mitochondrial respiration. Furthermore, E. coli induced apoptosis of DCs but A. faecalis did not. Regarding an underlying mechanism, A. faecalis—unlike E. coli—did not induce intracellular nitric oxide (NO) production in DCs due to the low activity of its lipopolysaccharide (LPS). Therefore, A. faecalis, an example of LRCs, may persist within intestinal lymphoid tissue because they elicit little NO production in DCs. In addition, the symbiotic DCs exhibit characteristic physiologic changes, including a low rate of apoptosis and increased mitochondrial respiration.

In the current study, a soil bacterial isolate F2 expressed a significant antagonistic activity against Candida albicans ATCC 10231 and Aspergillus niger clinical isolate confirmed through cross streak, dual culture, and agar well diffusion methods. The isolate F2 was identified using phenotypic and molecular approaches as Alcaligenes (A.) faecalis MT332429. The identification and structural characterization of the antifungal compound was performed using advanced spectroscopic techniques including UV absorbance, 1H and 13C NMR and 2D NMR (COSY, HSQC, and HMBC) and was identified as octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate. Response surface methodology (RSM) using a central composite design was employed to optimize the nutritional and cultural variables affecting the antifungal metabolite yield. The optimum conditions were found to be temperature 30 °C, agitation 150 rpm, glucose 1 g/l, peptone 2 g/l, and pH 8. A confirmatory experiment was performed to assess the accuracy of the optimization procedure, where an increase in the antifungal metabolite production by about 2.48-fold was obtained. To the best of our knowledge, this is the first report of octadecyl 3-(3, 5-di-tert-butyl-4-hydroxyphenyl) propanoate recovered from the culture broth of A. faecalis MT332429 with a promising antifungal activity along with its optimized production through RSM. • A novel soil bacterial isolate, F2, identified as Alcaligenes faecalis MT332429, showed significant antagonistic activity against Candida albicans ATCC 10231 and Aspergillus niger clinical isolate. • This stable fungicidal extracellular metabolite was identified as octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate. • Optimization using central composite design resulted in 2.48-fold increase in production reaching 213.82 μg/ml.

Biofilm formation by monocultures and mixed cultures of nitrile-hydrolyzing bacteria Alcaligenes faecalis 2 and Rhodococcus ruber gt 1 was studied. Biofilm formation was assessed by staining with Crystal violet, by the energy state of the cells, and by the output of the polymer matrix. A quantitative method for assessment of the output of the polymer matrix by the fluorescence of konA-tetramethylrhodamine was developed. The medium used for obtaining mixed biofilms of Al. faecalis 2 and R. ruber gt 1 contained acetamide and glucose as carbon sources. In mixed biofilms Al. faecalis 2 was shown to act as a primary colonizer, while R. ruber gt 1 was a satellite microorganism. Compared to monoculture biofilms, mixed biofilms exhibited higher output of the polymer matrix and increased biofilm formation by Al. faecalis 2 and R. ruber gt 1 on addition of the culture liquid of the second strain. Daily addition of the toxic substrate acetonitrile to planktonic and biofilm cultures resulted in bacterial adaptation, as was indicated by higher numbers of surviving cells compared to the variants with acetonitrile addition every 10 min, mainly due to nitrile hydratase activity of R. ruber gt 1, which transformed acetonitrile into nontoxic acetamide. Our results show that binary biofilms of amidase-containing Al. faecalis 2 and R. ruber gt 1, a strain with high nitrile hydratase activity, are promising as biocatalysts for acrylic acid production and as the basis for a biofilter for nitrile removal from wastewater.

A biocatalytic process for synthesis of acrylic acid was studied in the presence of Rhodococcus erythropolis 4-1 and Alcaligenes faecalis 2 strains with the pronounced amidase activity. The optimal pH of the process was 6–7 for R. erythropolis 4-1 and 7–7.5 for A. faecalis 2, optimal temperature 20–50 °C for both strains, optimal concentration of acrylamide 150 mM for R. erythropolis 4-1 and 250 mM for A. faecalis 2. At the stepwise addition of the substrate, the synthesis was more effective with A. faecalis 2 than with R. erythropolis 4-1. Freezing at –20 °C was shown preferable for storing the biocatalysts. The amidase activity of both humid and dry stored A. faecalis 2 cells immobilized on activated glutaric aldehyde and non-activated chitosan was not decreased.

In the present study, arsenic tolerant bacteria were isolated and characterized from rhizospheric soil of rice plant growing in the arsenic contaminated area of West Bengal, India. Among 31 bacterial isolates, nine isolates were showed tolerance at higher concentration of arsenate (As V; 20000 mg mL-1). Selected arsenic tolerance bacterial isolates were characterized based on biochemical analysis, partial 16S rDNA gene sequencing and phylogenetic analysis. Results revealed that selected arsenic tolerant bacterial strains were lavished at 370C and neutral pH 7 and showed a positive response for catalase and oxidase enzymes. Using partial 16S rDNA based identification and phylogenetic analysis, selected bacterial isolates were identified as Jeotgalicoccus nanhaiensis, Alcaligenes faecalis, Paenalcaligenes sp., Providencia sp., Kocuria sp. and Pseudomonas stutzeri. Further, the isolated As tolerant bacterial strains may be tested for their possible utilization in arsenic mobilization in the rhizosphere for enhancing phytoremediation potential to remediate arsenic from contaminated sites. However, efficient arsenic accumulator strain like Pseudomonas stutzeri can be employed as bioresource to develop low-cost bioremediation technology for arsenic removal.

Some microorganisms can utilize photoelectrons and electrode electrons. Exogenous electrons generate enough energy for growth, and electron shuttles may accelerate this process. This research data supported photoelectron-responsive microorganism Alcaligenes faecalis was effected by the growth metabolism due to bias and electron shuttle riboflavin (RF) with an adaptive screening voltage under oligotrophic conditions. A slight change was observed in the redox property of RF. RF played the role of an electron shuttle. Microbial extracellular metabolites could bind additional nicotinamide adenine dinucleotide (NADH) species with RF. The intracellular protein content in the group of RF–Bias was 1.94, 1.93 and 4.02 times higher than those in the RF, bias and control groups, respectively, while the corresponding intracellular contents of humus were 1.10, 0.93 and 1.42 times higher. The content of CoA in RF–Bias, RF and bias increased to 116.0%, 108.5% and 103.8%, respectively. The organic acids of the RF–Bias group in the Krebs cycle are more advanced than those of other groups. Overall, in the Krebs cycle, RF and bias facilitated the growth and metabolism of A. faecalis. Finally, a mechanism was proposed, showing that the electron transfer chain and the Krebs cycle are stimulated by RF and bias.

Microbial Enhanced Oil Recovery (MEOR) is a term which is attributed to the process of utilizing bacterial activity for increasing the recovery factor of oil reservoirs. This process relies on several mechanisms especially interfacial tension reduction and wettability alteration mechanisms. The main purpose of this work is to evaluate the impact of these mechanisms during MEOR process for microorganism isolated from formation water of one of the Iranian southwest carbonate oil reservoirs. The isolated microorganism was identified to be Alcaligenes faecalis. The optimum condition for growth of microorganism was found at 28 °C, pH = 7, carbon to nitrogen ratio of 30 and 3% salinity. Results show that the selected microorganism is able to reduce the interfacial tension between formation brine and crude oil from 28.1 mN/m to 8.4 mN/m and alter the wettability of reservoir rock from approximately 156° to 86° which represents a change from oil-wet condition toward intermediate-wet. Results show that the isolated microorganism is able to produce 8.2% and 5.2% additional oil recovery in respective shut in and quick flooding scenarios. This show that the isolated microorganism is efficient in production of additional oil as a part of tertiary oil recovery process.

Various types of pigments are produced by different bacterial species and play multifunctional role including their role as a protective agent against environmental stresses. The present study deals with the isolation and characterization of melanin pigment from bacteria. Three isolates showed pigment production and identified as Klebsiella pneumoniae S-1, Alcaligenes faecalis PBI and Enterobacter sp. ABI on the basis of 16S rRNA gene sequencing. The maximum production of brown pigment (λmax 405 nm) was attained after 6 days of growth in liquid medium containing 3 g L−1 of l -tyrosine. Solubility test, FTIR and ESI-MS analysis suggested the nature of pigment as melanin. Identity of pigment type from all the three bacteria was made by HPLC analysis, results showed the presence of homogentisic acid (HGA), a precursor of pyomelanin. All the bacteria showed high activity of 4-hydroxyphenylpyruvate dioxygenase (HPPD) suggesting its role in HGA synthesis. PCR amplification of gene(s) also showed the presence of 4-hydroxyphenylpyruvate dioxygenase (hppD) gene coding for HPPD enzyme suggesting its role in pyomelanin synthesis. This study deals with only three bacterial isolates, isolation of such pigment from a large number of bacteria growing in harsh habitats may prove useful in finding novel type of melanin.

Rhizoremediation is a strategy where pollutant degrading bacteria are augmented through plant roots using plant-microbe interaction. Therefore, for effective rhizoremediation of pyrene contaminated soil, bacterial strains were experimented for amelioration of stress response in host plant along with biodegradation ability. A total of 28 bacteria, having ability to degrade polycyclic aromatic hydrocarbons were isolated from contaminated sites and checked for their plant growth promoting attributes, such as indole acetic acid (IAA) production, phosphate solubilization, atmospheric nitrogen fixation and siderophore release. Among these isolates, Klebsiella pneumoniae AWD5 was found to degrade 60% of pyrene. While other isolates, i.e. Alcaligenes faecalis BDB4, Pseudomonas fragi DBC, Pseudomonas aeruginosa PDB1, Acinetobactor sp. PDB4 degraded 48.5%, 50.29%, 31.3% and 36% of pyrene, respectively, after 6 days of incubation. K. pneumoniae AWD5 produced 94.2 μg/ml IAA and 3.1 mM/mg/h unit of ACC deaminase, which was best among eighteen indole acetic acid producers and five of the 1-aminocyclopropane-1-carboxylate (ACC) deaminase producing isolates. P. aeruginosa PDB1 resulted in highest phosphate solubilization activity of 875.26 ng/ml of soluble phosphate among seven phosphate solubilizers. The isolates AWD5 and PDB1 both have shown a good amount of siderophore release (56.3% and 84.3% unit). There was 19.1% increase in shoot length of rice seedlings treated with PDB1 in presence of pyrene. Similarly, 26.5% increase in the root length of AWD5 treated rice was recorded in pyrene contaminated soil. Bacterial inoculation also induced and improved the stress response in host plant, in presence of pyrene, as suggested by the superoxide dismutase, glutathione and glutathione-S-transferase activities in rice.

Biocatalytic cyclization is highly desirable for efficient synthesis of biologically derived chemical substances, such as the commodity chemicals ε-caprolactam and δ-valerolactam. To identify biocatalysts in lactam biosynthesis, we develop a caprolactam-detecting genetic enzyme screening system (CL-GESS). The Alcaligenes faecalis regulatory protein NitR is adopted for the highly specific detection of lactam compounds against lactam biosynthetic intermediates. We further systematically optimize the genetic components of the CL-GESS to enhance sensitivity, achieving 10-fold improvement. Using this highly sensitive GESS, we screen marine metagenomes and find an enzyme that cyclizes ω-amino fatty acids to lactam. Moreover, we determine the X-ray crystal structure and catalytic residues based on mutational analysis of the cyclase. The cyclase is also used as a helper enzyme to sense intracellular ω-amino fatty acids. We expect this simple and accurate biosensor to have wide-ranging applications in rapid screening of new lactam-synthesizing enzymes and metabolic engineering for lactam bio-production., Efficient biosynthesis of lactams is still undesirable due to lacking of suitable enzyme. Here, the authors develop a sensitive transcription factor-based biosensor for high-throughput screening of marine metagenome and find a cyclase that can cyclize ω-amino fatty acids to lactam.

Methane (CH4) and nitrous oxide (N2O) emissions from two-stage membrane bioreactor (MBR) bio-augmented by Alcaligenes faecalis no. 4 during municipal solid waste leachate treatment were investigate...

The whole cell arylacetonitrilase of Alcaligenes faecalis MTCC 12629 was employed to develop a bioprocess for the synthesis of 4-hydroxyphenylacetic acid (4-HPAA) from 4-hydroxyphenylacetonitrile (4-HPAN). Isobutyronitrile emerged as the most appropriate inducer with a 1.2-fold enhanced nitrilase production in inducer feeding approach. A. faecalis MTCC 12629 nitrilase preferably hydrolyzed 4-HPAN, 4-aminoyphenylacetonitrile, mandelonitrile and phenylacetonitrile to their corresponding acids. Thermostability profile revealed the stability of nitrilase at 40, 45 and 50°C with the half-life of 45 h, 36 h and 13 h, respectively. Michaelis constant (Km) and reaction velocity (Vmax) of nitrilase were calculated as 20 mM and 2 U/mg dcw, respectively. This nitrilase exhibited complete conversion of 4-HPAN to 4-HPAA at 45°C in 50 mM K2HPO4/KH2PO4 buffer (pH 7.0) in 30 min. A fed batch process designed at 500 ml with five feedings of substrate resulted in 150 mM product formation using 18 U/ml whole cells nitrilase (16 mg/ml dcw) at 45°C. This is the first report on the production of 4-HPAA through nitrilase mediated pathway with the volumetric and catalytic productivity of 23 g/l and 4.13 g/g dcw/h, respectively.

A novel and ecofriendly procedure was developed for the synthesis of silver nanoparticles (FAgNPs) with the reduction of AgNO3. The flavonoids fractions (FF) of Psidium guajava leaves (PGL) were used as a green reducing and capping agent. Results showed that FF from PGL rapidly could synthesize into regular spheres and stable silver nanoparticles within 10 min. The average particle size of synthesized FAgNPs was 15–20 nm, with maximum absorbance wavelength at 420 nm. Moreover, FAgNPs exhibited a strong inhibition against the selected microorganisms, especially Alcaligenes faecalis, Escherichia coli and Aspergillus niger. Importantly, FAgNPs also possessed good catalytic degradation potency for organic dyes, namely, methyl orange and Coomassie brilliant blue G-250, under solar or UV irradiation. Overall, FAgNPs have good potential application prospects in the development of anti-bacterial materials and for the photocatalytic degradation of certain toxic dyes or chemicals, thereby paving the way for waste treatment and environmental bio-remediation.

The green synthesis of nanoparticles has become increasingly promising due to their potential applications in nanomedicine and materials science. In this study, silver nanoparticles (P-AgNPs) were synthesized from aqueous extracts of P. guajava L. leaf. The synthesized silver nanoparticles were confirmed by UV–vis spectrophotometry at 438 nm. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and zetasizer analyses showed that the average sizes of the P-AgNPs were 20–35 nm, 25 nm, and 25–35 nm, respectively. Element mapping analyses of the P-AgNPs were confirmed by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) analyses. Moreover, FTIR spectra of the synthesized P-AgNPs showed the presence of phyto constituents as capping agents. Zeta potential measurements (−20.17 mV) showed that the synthesized P-AgNPs had reasonably good stability. The in vitro antioxidant properties of the P-AgNPs were evaluated using two different methods. A highly efficient radical scavenging activity of P-AgNPs possessing IC50 values of 52.53 ± 0.31 μg/mL (DPPH) and 55.10 ± 0.29 μg/mL (ABTS+) were confirmed. At a concentration of 100 μg/mL, antimicrobial activity assays of the P-AgNPs showed significant inhibition against selected bacteria, S. cerevisiae, A. niger and R. oryzae, especially against Alcaligenes faecalis and Escherichia coli. The present study revealed that the low-cost and environmentally friendly synthesis of P-AgNPs can be widely used in biomedicine, water treatment or purification, and nanobiotechnology.