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Plastics have accumulated in open environments, such as oceans, rivers, and land, for centuries, but their effect has been of concern for only decades. Plastic pollution is a global challenge at the forefront of public awareness worldwide due to its negative effects on ecological systems, animals, human health, and national economies. Therefore, interest has increased regarding specific circular economies for the development of plastic production and the investigation of green technologies for plastic degradation after use on an appropriate timescale. Moreover, biodegradable plastics have been found to contain potential new hazards compared with conventional plastics due to the physicochemical properties of the polymers involved. Recently, plastic biodegradation was defined as microbial conversion using functional microorganisms and their enzymatic systems. This is a promising strategy for depolymerizing organic components into carbon dioxide, methane, water, new biomass, and other higher value bioproducts under both oxic and anoxic conditions. This study reviews microplastic pollution, the negative consequences of plastic use, and the current technologies used for plastic degradation and biodegradation mediated by microorganisms with their drawbacks; in particular, the important and questionable role of extremophilic multi-enzyme-producing bacteria in synergistic systems of plastic decomposition is discussed. This study emphasizes the key points for enhancing the plastic degradation process using extremophiles, such as cell hydrophobicity, amyloid protein, and other relevant factors. Bioprospecting for novel mechanisms with unknown information about the bioproducts produced during the plastic degradation process is also mentioned in this review with the significant goals of CO2 evolution and increasing H2/CH4 production in the future. Based on the potential factors that were analyzed, there may be new ideas for in vitro isolation techniques for unculturable/multiple-enzyme-producing bacteria and extremophiles from various polluted environments.
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The brightly colored synthetic dyes used in the textile industry are discharged at high concentrations-for example, various azo dyes including Methylene Blue (MB) and Methyl Orange (MO)-which is a matter of global concern, as such dyes are harmful to humans and the environment. Microbial degradation is considered an efficient alternative for overcoming the disadvantages of conventional physical and chemical dye removal methods. In this study, we investigated the potential of multiple types of the enzyme-producing extremophilic bacteria Bacillus FW2, isolated from food waste leachate, for the decolorization and bioremediation of artificial synthetic dyes. The screening of enzyme production and assaying of bacterial strain enzymes are essential for enhancing the breakdown of azo bonds in textile azo dyes. The degradation efficiencies of the water-soluble dyes MB and MO were determined at different concentrations using rice husk, which is an efficient substrate. Using the rice husks, the MO was removed completely within 20 h, and an estimated 99.8% of MB was degraded after 24 h by employing shaking at 120 rpm at 40 °C-whereas a removal efficiency of 98.9% was achieved for the combination of MB + MO. These results indicate the possibility of applying an extremophilic bacterial strain, Bacillus sp., for large-scale dye degradation in the future.
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Biological treatment methods overcome many of the drawbacks of physicochemical strategies and play a significant role in removing dye contamination for environmental sustainability. Numerous microorganisms have been investigated as promising dye-degrading candidates because of their high metabolic potential. However, few can be applied on a large scale because of the extremely harsh conditions in effluents polluted with multiple dyes, such as alkaline pH, high salinity/heavy metals/dye concentration, high temperature, and oxidative stress. Therefore, extremophilic microorganisms offer enormous opportunities for practical biodegradation processes as they are naturally adapted to multi-stress conditions due to the special structure of their cell wall, capsule, S-layer proteins, extracellular polymer substances (EPS), and siderophores structural and functional properties such as poly-enzymes produced. This review provides scientific information for a broader understanding of general dyes, their toxicity, and their harmful effects. The advantages and disadvantages of physicochemical methods are also highlighted and compared to those of microbial strategies. New techniques and methodologies used in recent studies are briefly summarized and discussed. In particular, this study addresses the key adaptation mechanisms, whole-cell, enzymatic degradation, and non-enzymatic pathways in aerobic, anaerobic, and combination conditions of extremophiles in dye degradation and decolorization. Furthermore, they have special metabolic pathways and protein frameworks that contribute significantly to the complete mineralization and decolorization of the dye when all functions are turned on. The high potential efficiency of microbial degradation by unculturable and multi-enzyme-producing extremophiles remains a question that needs to be answered in practical research.
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Rapid industrialization has led to the pollution of soil and water by various types of contaminants. Heavy metals (HMs) are considered the most reactive toxic contaminants, even at low concentrations, which cause health problems through accumulation in the food chain and water. Remediation using conventional methods, including physical and chemical techniques, is a costly treatment process and generates toxic by-products, which may negatively affect the surrounding environment. Therefore, biosorption has attracted significant research interest in the recent decades. In contrast to existing methods, bacterial biomass offers a potential alternative for recovering toxic/persistent HMs from the environment through different mechanisms for metal ion uptake. This review provides an outlook of the advantages and disadvantages of the current bioremediation technologies and describes bacterial groups, especially extremophiles with biosorbent potential for heavy metal removal with relevant examples and perspectives.
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Facing the crucial issue of high cost in cellulase production from commercial celluloses, inexpensive lignocellulosic materials from agricultural wastes have been attractive. Therefore, several studies have focused on increasing the efficiency of cellulase production by potential microorganisms capable of secreting a high and diversified amount of enzymes using agricultural waste as valuable substrates. Especially, extremophilic bacteria play an important role in biorefinery due to their high value catalytic enzymes that are active even under harsh environmental conditions. Therefore, in this study, we aim to investigate the ability to produce cellulase from coconut-mesocarp of the potential bacterial strain FW2 that was isolated from kitchen food waste in South Korea. This strain was tolerant in a wide range of temperature (-6-75 °C, pH range (4.5-12)) and at high salt concentration up to 35% NaCl. The molecular weight of the purified cellulase produced from strain FW2 was estimated to be 55 kDa. Optimal conditions for the enzyme activity using commercial substrates were found to be 40-50 °C, pH 7.0-7.5, and 0-10% NaCl observed in 920 U/mL of CMCase, 1300 U/mL of Avicelase, and 150 U/mL of FPase. It was achieved in 650 U/mL, 720 U/mL, and 140 U/mL of CMCase, Avicelase, and FPase using coconut-mesocarp, respectively. The results revealed that enzyme production by strain FW2 may have significant commercial values for industry, argo-waste treatment, and other potential applications.
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It has become urgent to develop cost-effective and clean technologies for the rapid and efficient treatment of food waste leachate, caused by the rapid accumulation of food waste volume. Moreover, to face the energy crisis, and to avoid dependence on non-renewable energy sources, the investigation of new sustainable and renewable energy sources from organic waste to energy conversion is an attractive option. Green energy biohydrogen production from food waste leachate, using a microbial pathway, is one of the most efficient technologies, due to its eco-friendly nature and high energy yield. Therefore, the present study aimed to evaluate the ability of an enriched bacterial mixture, isolated from forest soil, to enhance hydrogen production from food waste leachate using biochar. A lab-scale analysis was conducted at 35 °C and at different pH values (4, no adjustment, 6, 6.5, 7, and 7.5) over a period of 15 days. The sample with the enriched bacterial mixture supplemented with an optimum of 10 g/L of biochar showed the highest performance, with a maximum hydrogen yield of 1620 mL/day on day three. The total solid and volatile solid removal rates were 78.5% and 75% after 15 days, respectively. Acetic and butyrate acids were the dominant volatile fatty acids produced during the process, as favorable metabolic pathways for accelerating hydrogen production.
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Compared to lipases from plants or animals, microbial lipases play a vital role in different industrial applications and biotechnological perspectives due to their high stability and cost-effectiveness. Therefore, numerous lipase producers have been investigated in a variety of environments in the presence of lipidic carbon and organic nitrogen sources. As a step in the development of cultivating the unculturable functional bacteria in this study, the forest soil collected from the surrounding plant roots was used to create an artificially contaminated environment for lipase-producing bacterial isolation. The ten strongest active bacterial strains were tested in an enzyme assay supplemented with metal ions such as Ca2+, Zn2+, Cu2+, Fe2+, Mg2+, K+, Co2+, Mn2+, and Sn2+ to determine bacterial tolerance and the effect of these metal ions on enzyme activity. Lipolytic bacteria in this study tended to grow and achieved a high lipase activity at temperatures of 35-40 °C and at pH 6-7, reaching a peak of 480 U/mL and 420 U/mL produced by Lysinibacillus PL33 and Lysinibacillus PL35, respectively. These potential lipase-producing bacteria are excellent candidates for large-scale applications in the future.
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Strain NHI-1T is a Gram-negative, motile, non-spore-forming bacterium isolated from oil-contaminated soil in South Korea. The strain was able to grow by using gasoline, diesel and kerosene as energy and carbon sources. After incubation for 14âdays, cells (1âg l- 1) degraded approximately 58 % of oil present at concentration of 1500âp.p.m. at pH 8 and 28 °C. Strain NHI-1T grew well under aerobic conditions, with optimal growth at pH 7-9 and 28 °C-37 °C but grew poorly in the presence of ≥ 0.5 % NaCl. Phylogenetic analyses based on 16S rRNA gene sequences indicated that the closest relatives of strain NHI-1T were Aquabacterium fontiphilum CS-6T (97.96 % sequence similarity), Aquabacterium parvum B6T (96.39 %), Aquabacterium commune B8T (95.76 %), Aquabacterium limnoticum ABP-4T (95.72 %) and Aquabacterium citratiphilum B4T (95.25 %). DNA-DNA relatedness was 41-53 % between strain NHI-1T and its closest type strains. The major fatty acids present in strain NHI-1T were summed feature 3 (C16 : 1ω7c/C16 : 1ω6c, 44.5 %), summed feature 8 (C18 : 1ω7c/C18 : 1ω6c, 21.5 %) and C16 : 0 (16.2 %), and the predominant polar lipids were phosphatidylglycerol, phosphatidylethanolamine, phosphatidylserine, diphosphatidylglycerol and uncharacterized aminophospholipids. Strain NHI-1T was distinguishable from other members of genus Aquabacterium based on phenotypic, chemotaxonomic and genotypic characteristics. Therefore, strain NHI-1T represents a novel species of the genus Aquabacterium for which the name Aquabacterium olei sp. nov. is proposed. The type strain is NHI-1T ( = KEMB 9005-082T = KACC 18244T = NBRC 110486T).
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Betaproteobacteria/clasificación , Contaminación por Petróleo , Filogenia , Microbiología del Suelo , Técnicas de Tipificación Bacteriana , Composición de Base , Betaproteobacteria/genética , Betaproteobacteria/aislamiento & purificación , ADN Bacteriano/genética , Ácidos Grasos/química , Datos de Secuencia Molecular , Hibridación de Ácido Nucleico , Fosfolípidos/química , ARN Ribosómico 16S/genética , República de Corea , Análisis de Secuencia de ADN , Contaminantes del SueloRESUMEN
A novel, aerobic, psychrotolerant, Gram-stain-positive, endospore-forming strain, NHI-2(T), was isolated from oil-contaminated soil near a gas station in Mongolia. This strain was characterized by motile rods and grew over a wide range of temperatures ( -2 to 40 °C) with optimal growth at 28-30 °C. It tolerated salt concentrations of up to 7% over a five-day incubation period. Analysis of 16S rRNA gene sequence indicated that strain NHI-2(T) belongs to the genus Psychrobacillus. Sequence similarity between NHI-2(T) and members of the genus Psychrobacillus with validly published names ranged from 97.83 to 98.18%. DNA-DNA hybridization indicated less than 70% relatedness to reference strains within the genus. The G+C content of the genomic DNA was 36 mol%. This strain contained MK-8 as a predominant isoprenoid menaquinone. NHI-2(T) had ornithine in the cell wall similar to reference strains of the genus Psychrobacillus. The major fatty acids present in NHI-2(T )were anteiso-C15 : 0 (51.0%), iso-C15 : 0 (9.1%) and anteiso-C17 : 0 (8.0%). The major polar lipids were phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylglycerol. These data highlight that the phenotype of strain NHI-2(T) differs from that of related species in terms of chemotaxonomic properties and genotype characteristics. Therefore, this strain is proposed as a representative of a novel species, named Psychrobacillus soli. The type strain is NHI-2(T) ( = KEMB 9005-135(T) = KACC 18243(T) = NBRC 110600(T)).
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Psychrobacter , Microbiología del Suelo , Bacillaceae/clasificación , Composición de Base , ADN Bacteriano , Contaminación Ambiental , Ácidos Grasos/análisis , Datos de Secuencia Molecular , Mongolia , Hibridación de Ácido Nucleico , Filogenia , Psychrobacter/aislamiento & purificación , Psychrobacter/metabolismo , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN , SueloRESUMEN
Strain NHI-8(T) was isolated from a forest soil sample, collected in South Korea, by using a modified culture method. Comparative analysis of its nearly full-length 16S rRNA gene sequence showed that strain NHI-8(T) belongs to the genus Mesorhizobium and to be closely related to Mesorhizobium chacoense PR5(T) (97.32 %). The levels of DNA-DNA relatedness between strain NHI-8(T) and reference type strains of the genus Mesorhizobium were 32.28-53.65 %. SDS-PAGE of total soluble proteins and the sequences of the housekeeping genes recA, glnII, and atpD were also used to support the clade grouping in rhizobia. The new strain contained summed feature 8 (57.0 %), cyclo-C19:0ω8c (17.3 %), and C18:0 (11.0 %) as the major fatty acids, as in genus Mesorhizobium. The strain contained cardiolipin, phosphatidylglycerol, ornithine-containing lipid, phosphatidylethanolamine, phosphatidyl-N-dimethylethanolamine, and phosphatidylcholine. Morphological and physiological analyses were performed to compare the characteristics of our strain with those of the reference type strains. Based on the results, strain NHI-8(T) was determined to represent a novel member of the genus Mesorhizobium, and the name Mesorhizobium soli is proposed. The type strain is NHI-8(T) (=KEMB 9005-153(T) = KACC 17916(T) = JCM 19897(T)).