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Abstract Exopolysaccharides (EPSs), a constitutive part of bacterial biofilm, act as a protecting sheath to the extremophilic bacteria and are of high industrial value. In this study, we elucidate a new EPS produced by thermotolerant (growth from 34–44 °C) strain Pseudomonas alcaligenes Med1 from Medano hot spring (39.1 °C surface temperature, pH 7.1) located in the Central Andean Mountains of Chile. Bacterial growth was screened for temperature tolerance (10–60 °C) to confirm the thermotolerance behaviour. Physicochemical properties of the EPS were characterized by different techniques: Scanning Electron Microscopy- Energy Dispersive X-ray Spectroscopy (SEM-EDS), Atomic Force Microscopy (AFM), High-Performance Liquid Chromatography (HPLC), Gel permeation chromatography (GPC), Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR), and Thermogravimetric analysis (TGA). Whole genome of P. alcaligenes Med1 has also been studied in detail to correlate the structural and functional characteristics with genomic insight. The EPS demonstrated amorphous surface roughness composed of evenly distributed macromolecular lumps composed of mainly carbon and oxygen. The monosaccharide analysis has shown the presence of glucose, galactose, and mannose sugars at different ratios. TGA revealed the high thermal stability (315.3 °C) of the polysaccharide. The GPC has shown that Med1 is a low molecular weight polysaccharide (34.8 kDa) with low PI. The 2D-NMR linkage analysis suggests a diverse array of glycosidic bonds within the exopolysaccharide structure. The functional properties of the EPS were evaluated for food industry applications, specifically for antioxidant (DPPH, FRAP an H2O2). Extracted Med1 EPS revealed significant emulsification activity against different food grade vegetative oils (Coconut oil, Corn oil, Canola oil, Avocado oil, Sunflower oil, Olive oil, and Sesame oil). The highest 33.9% flocculation activity was observed with 60 mg L−1 EPS concentration. It showed water-holding (WHC) of 107.6% and oil-holding (OHC) capacity of 110.8%. The functional EPS produced by Pseudomonas alcaligenes Med1 from Central Andean Chilean hot spring of central Chile can be a useful additive for the food-processing industry.

Background: At present, research on facile, green synthesis of nanoparticles has significantly increased because of its fast, one-step, cost-effective, time-efficient, and non-toxic nature. In this study, we have reported a single-step green synthesis of copper nanoparticles using cell wall polysaccharides of a hot spring origin, thermotolerant Bacillus species. Result: Copper nanoparticles were characterized using UV-visible spectrophotometry, fluorescence and Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, particle size, and zeta potential analyses. UV-visible spectra of synthesized copper nanoparticles exhibited a band cantered between 220–235 nm, characteristic spectra of copper oxide nanoparticles. Infrared spectra showed the band at 490-530 cm−1 corresponding to metal-oxygen or copper nanoparticle vibration, supporting the presence of copper oxide nanoparticles in the monoclinic phase. The energy dispersive spectra of copper nanoparticles exhibited a strong signal from elemental copper. The dynamic Light Scattering pattern confirmed the nanoparticle nature of the studied sample. These nanoparticles showed preferential activity against gram-negative pathogens, Salmonella typhi and Escherichia coli. The thermodynamic nature of the nanoparticles is also established for its antibacterial actions. Conclusions: The antibacterial action and its thermodynamics reinforce the possible use of copper nanoparticles as an alternative to commercially available antimicrobials. This study may open a new path for future studies to treat harmful microorganisms resistant to traditional antibiotics in a greener way.How to cite: Banerjee A, Roy RK, Sarkar S, et al. Synthesis of hot spring origin bacterial cell wall polysaccharide-based copper nanoparticles with antibacterial property. Electron J Biotechnol 2024;68. https://doi.org/10.1016/j.ejbt.2023.11.005.

Xylose Isomerase (XI) is an intramolecular oxidoreductase enzyme and catalyzes the reversible conversion of ketoses and aldoses in addition to the bioconversion of ethanol from xylose in the production of bioethanol from hemicellulose. It has a broad range of industrial applications in the food and pharmaceutical sectors, particularly in the production of the sweetener high fructose corn syrup (HFCS). It is one of the most widely used industrial enzymes after protease. Taking this into consideration, four bacterial XI sources were selected based on growth temperature, i.e., psychrophile, mesophile, thermophile, and hyperthermophile, for analyzing Xylose Isomerase’s structure-function characteristics. It was found that thermophilic XI was structurally less stable than mesophilic and hyperthermophilic XI, whereas structural plasticity ran opposite towards mesophiles. The interaction of xylose isomerase (XI) with two ligands, namely Amino-2-Hydroxymethyl-Propane-1,3-Diol and (4R)-2-Methylpentane-2,4- Diol, was also studied. Mesophilic XI demonstrated better binding affinity with structurally stabilizing amino acids (Ala, Asp, Gly, Leu, and Arg). In comparison, Thermophilic XI showed nearly similar binding affinity with both Amino-2-Hydroxymethyl-Propane-1,3-Diol and (4R)-2-Methylpentane-2,4-Diol. The results of this investigation suggest that thermophilic XI, followed by mesophilic XI, would be the most appropriate for establishing process stability and sustainability in the food industry.

Abstract Contamination of soil by antibiotics and heavy metals originating from hospital facilities has emerged as a major cause for the development of resistant microbes. We collected soil samples surrounding a hospital effluent and measured the resistance of bacterial isolates against multiple antibiotics and heavy metals. One strain BMCSI 3 was found to be sensitive to all tested antibiotics. However, it was resistant to many heavy metals and metalloids like cadmium, chromium, copper, mercury, arsenic, and others. This strain was motile and potentially spore-forming. Whole-genome shotgun assembly of BMCSI 3 produced 4.95 Mb genome with 4,638 protein-coding genes. The taxonomic and phylogenetic analysis revealed it, to be a Bordetella petrii strain. Multiple genomic islands carrying mobile genetic elements; coding for heavy metal resistant genes, response regulators or transcription factors, transporters, and multi-drug efflux pumps were identified from the genome. A comparative genomic analysis of BMCSI 3 with annotated genomes of other free-living B. petrii revealed the presence of multiple transposable elements and several genes involved in stress response and metabolism. This study provides insights into how genomic reorganization and plasticity results in evolution of heavy metals resistance by acquiring genes from its natural environment.

Salinity abiotic stress is increasing day by day due to continuous global warming and climate change. This is also becoming one of the major causes behind the reduction in crop production. Plant–bacteria interaction plays an essential role in improving crop yield without using any chemical fertilizers. The present study aims to characterize the interaction between plant-growth-promoting bacteria (PGPB) and their role in mitigating salinity stress for local variety crops. Therefore, in this work, two PGPB, namely, Bacillus proteolyticus Cyn1 and Bacillus safensis Cyn2, were isolated from rhizospheric soil of the Chilean common bean ecotype “Sapito” (Phaseolus vulgaris L.), and their PGPB traits were analyzed. Cyn1 can produce NH3 and HCN and also secrete siderophores, whereas Cyn2 produced NH3 and siderophores but responded negatively to HCN production. Both the isolated bacteria have shown a positive result for ACC deaminase production, phosphate solubilization, and catalase enzyme secretion. Under all three tested abiotic stresses, i.e., temperature, water, and salinity, both the bacteria and their consortium have demonstrated positive responses. Cyn1 under temperature stress and water stress can produce a biofilm network to combat the stress. While under salinity stress, both the PGPB isolates indicated the production of stress components and cytoplasmic inclusion bodies. Based on the response, among all other abiotic stresses, salinity stress was chosen for further plant–bacteria interaction study and growth. Visible root colonization of the bacteria has been observed in comparison to the control. The germination index was 100% for all experimental setups of seed bacterization, both under control conditions and salinity stress. Both bacteria responded with good PGP traits that helped in the growth of healthy plants after the bacterial treatment in final pot experiments. Additionally, the consortium and the plants treated with Cyn1 have demonstrated high production of photosynthetic pigments in both experimental setups. Both B. proteolyticus Cyn1 and B. safensis Cyn2 have shown promising PGP characters and efficient response against toxicity related to salinity. Hence, both of these bacteria and consortium can be used for improved agricultural production of Chilean native common beans in the near future.

Plastic waste is the biggest global problem in present times due to its constant bioaccumulation in the environment. During the last year, 367 Mt of plastics were produced in the world, of which 28.6 Mt correspond to polyurethane waste. Polyurethanes can be found in products such as adhesives, preservatives, and foams, and are often difficult to recycle. The fragmentation of plastic waste in the environment generates microplastics causing a long-term effect on our ecosystem. In search of its solution via bioremediation using enzymes, in our present study cutinase enzyme has been chosen, as it appears to be a novel candidate due to the wide variety of substrates it hydrolyzes and its presence in different microorganisms. According to physiochemical characteristics, it was found that microbial cutinase enzymes are majorly made up of aliphatic amino acids. A higher aliphatic index (more than 80) indicates the great thermostability of the enzyme. Moreover, the enzyme is found to be hydrophilic and structurally stable. The negative GRAVY value of the enzyme confirmed its stable interaction with water. It was also observed that all chosen protein models had an average of 91.10 % amino acids in the favorable regions of the Ramachandran plot. The studied microbial cutinase enzymes from both fungi Humicola insolens and actinobacterium Thermobifida fusca successfully coupled with the polyurethane resin monomers. The main interactions were found in the catalytic triad with bonds close to the urethane bonds of the ligand, in addition to having an average binding energy of − 6 kJ/mol. The interaction between the cutinases with the PUR resin as a ligand was found to be evident from our study with stable binding energies, which makes microbial cutinases potential enzymes for polyurethane waste bioremediation processes.

Background: Arsenic contamination in the ground water of rural India is a recurrent problem and decontamination is mostly based on the chemical or physical treatments until now. Microbial bioremediation is eco-friendly, cheap, time-efficient and does not produce any toxic by-products. Result: In the present study, a high arsenic tolerant bacteria Brevundimonas aurantiaca PFAB1 was isolated from Panifala hot spring located in West Bengal, India. Previously Panifala was also reported to be an arsenic-rich hot spring. B. aurantiaca PFAB1 exhibited both positive arsenic reductase and arsenite oxidase activity. It was tolerant to arsenite up to 90 mM and arsenate up to 310 mM. Electron microscopy has proved significant changes in cellular micromorphology and stalk appearance under the presence of arsenic in growth medium. Bioaccumulation of arsenic in As (III) treated cells were 0.01% of the total cell weight, while 0.43% in case of As (V) treatment. Conclusions: All experimental lines of evidence prove the uptake/accumulation of arsenic within the bacterial cell. All these features will help in the exploitation of B. aurantiaca PFAB1 as a potent biological weapon to fight arsenic toxicity in the near future.How to cite: Banerjee A, Sarkar S, Gorai S, et al. High arsenic tolerance in Brevundimonas aurantiaca PFAB1 from an arsenic-rich Indian hot spring. Electron J Biotechnol 2021:52. https://doi.org/10.1016/j.ejbt.2021.05.006

Various microorganisms thrive under extreme environments, like hot springs, hydrothermal vents, deep marine ecosystems, hyperacid lakes, acid mine drainage, high UV exposure, and more. To survive against the deleterious effect of these extreme circumstances, they form a network of biofilm where exopolysaccharides (EPSs) comprise a substantial part. The EPSs are often polyanionic due to different functional groups in their structural backbone, including uronic acids, sulfated units, and phosphate groups. Altogether, these chemical groups provide EPSs with a negative charge allowing them to (a) act as ligands toward dissolved cations as well as trace, and toxic metals; (b) be tolerant to the presence of salts, surfactants, and alpha-hydroxyl acids; and (c) interface the solubilization of hydrocarbons. Owing to their unique structural and functional characteristics, EPSs are anticipated to be utilized industrially to remediation of metals, crude oil, and hydrocarbons from contaminated wastewaters, mines, and oil spills. The biotechnological advantages of extremophilic EPSs are more diverse than traditional biopolymers. The present review aims at discussing the mechanisms and strategies for using EPSs from extremophiles in industries and environment bioremediation. Additionally, the potential of EPSs as fascinating biomaterials to mediate biogenic nanoparticles synthesis and treat multicomponent water contaminants is discussed.

Background: Textile industry not only plays a vital role in our daily life but also a prominent factor in improving global economy. One of the environmental concern is it releases huge quantities of toxic dyes in the water leading to severe environmental pollution. Bacterial laccase and azoreductase successfully oxidize complex chemical structure of nitrogen group-containing azo dyes. Additionally, the presence of textile dye infuriates bacterial peroxidase to act as a dye degrading enzyme. Our present study deals with three textile dye degrading enzymes laccase, azoreductase, and peroxidase through analyzing their structural and functional properties using standard computational tools. Result: According to the comparative analysis of physicochemical characteristics, it was clear that laccase was mostly made up of basic amino acids whereas azoreductase and peroxidase both comprised of acidic amino acids. Higher aliphatic index ascertained the thermostability of all these three enzymes. Negative GRAVY value of the enzymes confirmed better water interaction of the enzymes. Instability index depicted that compared to laccase and preoxidase, azoreductase was more stable in nature. It was also observed that the three model proteins had more than 90% of total amino acids in the favored region of Ramachandran plot. Functional analysis revealed laccase as multicopper oxidase type enzyme and azoreductase as FMN dependent enzyme, while peroxidase consisted of α-β barrel with additional haem group. Conclusion: Present study aims to provide knowledge on industrial dye degrading enzymes, choosing the suitable enzyme for industrial set up and to help in understanding the experimental laboratory requirements as well.How to cite: Sarkar S, Banerjee A, Chakraborty N, et al. Structural-functional analyses of textile dye degrading azoreductase, laccase and peroxidase: a comparative in silico study. Electron J Biotechnol 2020;43. https://doi.org/10.1016/j.ejbt.2019.12.004 Keywords: Acidic amino acids, Azo dyes, Azoreductase, Basic amino acids, Dye degradation, Laccase, Peroxidase, Textile industry, Thermostable three enzymes

Extremophilic microorganisms often produce novel bioactive compounds to survive under harsh environmental conditions. Exopolysaccharides (EPSs), a constitutive part of bacterial biofilm, are functional biopolymers that act as a protecting sheath to the extremophilic bacteria and are of high industrial value. In this study, we elucidate a new EPS produced by thermophilic Bacillus haynesii CamB6 from a slightly acidic (pH 5.82) Campanario hot spring (56.4 °C) located in the Central Andean Mountains of Chile. Physicochemical properties of the EPS were characterized by different techniques: Scanning electron microscopy- energy dispersive X-ray spectroscopy (SEM-EDS), Atomic Force Microscopy (AFM), High-Performance Liquid Chromatography (HPLC), Gel permeation chromatography (GPC), Fourier Transform Infrared Spectroscopy (FTIR), 1D and 2D Nuclear Magnetic Resonance (NMR), and Thermogravimetric analysis (TGA). The EPS demonstrated amorphous surface roughness composed of evenly distributed macromolecular lumps. GPC and HPLC analysis showed that the EPS is a low molecular weight heteropolymer composed of mannose (66%), glucose (20%), and galactose (14%). FTIR analysis demonstrated the polysaccharide nature (–OH groups, Acetyl groups, and pyranosic ring structure) and the presence of different glycosidic linkages among sugar residues, which was further confirmed by NMR spectroscopic analyses. Moreover, D-mannose α-(1→2) and α-(1→4) linkages prevail in the CamB6 EPS structure. TGA revealed the high thermal stability (240 °C) of the polysaccharide. The functional properties of the EPS were evaluated for food industry applications, specifically as an antioxidant and for its emulsification, water-holding (WHC), oil-holding (OHC), and flocculation capacities. The results suggest that the study EPS can be a useful additive for the food-processing industry.