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Isolation of functional ligninolytic Bacillus aryabhattai from paper mill sludge and its lignin degradation potential.

ABSTRACT: Kraft lignin (KL), is the major pollutant in pulp and paper effluent and due to its heterogeneous structure, it is resistant to the depolymerization process. It has drawn much attention from the researcher due to its challenging degradation process. In this study, a KL-degrading bacterium was isolated and screened from paper mill sludge. This bacterium was identified as ligninolytic Bacillus aryabhattai using biochemical and 16SrRNA gene analysis. B. aryabhattai showed maximum activities of lignin peroxidase-LiP (0.74 IU mL^-1) and manganese peroxidase-MnP (9.2 IU mL^-1) on the 4th day, and 5th day, respectively. A total 84% of KL (500 mg L ^-1) reduction was observed after 14 days. The KL bio-degradation was confirmed based on changes in chemical stracture of KL and new metabolites identification using FTIR and GC-MS, respectively. The study concluded that B. aryabhattai maybe becomes a potential biological agent in KL biodegradation and treatment of other lignin-containing industrial effluents.

SUBMITTER: Singh A

PROVIDER: S-EPMC9307452 | biostudies-literature | 2022 Sep

REPOSITORIES: biostudies-literature

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Isolation of functional ligninolytic Bacillus aryabhattai from paper mill sludge and its lignin degradation potential.

Singh Anjali A Kumar Rajesh R Maurya Annapurna A Chowdhary Pankaj P Raj Abhay A

Biotechnology reports (Amsterdam, Netherlands) 20220718

Kraft lignin (KL), is the major pollutant in pulp and paper effluent and due to its heterogeneous structure, it is resistant to the depolymerization process. It has drawn much attention from the researcher due to its challenging degradation process. In this study, a KL-degrading bacterium was isolated and screened from paper mill sludge. This bacterium was identified as ligninolytic Bacillus aryabhattai using biochemical and 16SrRNA gene analysis. B. aryabhattai showed maximum acti ...[more]

PMID: 35880093

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Project description:BackgroundLignocellulosic biomasses produced from agriculture and forest-based industries are the cheapest or negative-cost biomass with a great potential for biotransformation to value-added bioproducts. Paper mill sludge, an important lignocellulosic biomass creates an environmental threat, which requires financial input for disposal. Thus, this study was aimed to isolate a novel bacterial strain capable of degrading cellulosic biomass including paper mill sludge to produce reducing sugar and other value-added bioproducts.ResultsA novel bacterial strain Arthrobacter woluwensis TDS9 isolated from the soil was screened for its cellulolytic activity using carboxymethyl cellulose (CMC) as the sole carbon source. The incubation period, temperature, pH, carbon, and nitrogen sources are the most important factors ruling the CMCase and sugar productions of the strain A. woluwensis TDS9, and an alkaline pH (pH 8.0) led to enhanced sugar production up to 1100.09 μg/mL after 72 h of incubation at 25°C in a medium containing 1.5% CMC and 1.25% beef extract. The optimal conditions for maximum CMCase activity were defined, and the potassium ion boosted the CMCase activity up to 1.06 U/mL when the enzymatic reaction was performed for 30 min at 50°C and pH 8 using CMC as a substrate. Moreover, the strain A. woluwensis TDS9 produced 433.33 μg/mL reducing sugar from 1% pretreated paper mill sludge. Significant alterations in the structural arrangement of cellulosic fiber of paper mill sludge observed under microscope after each step of chemical treatment process helped for loosening the cellulose fibers and increased the saccharification for enzymatic hydrolysis. Endoglucanase IV (33 KDa) and beta-glucosidase II (53 KDa) were identified in crude enzyme based on the zymogram analysis and substrate specificity.ConclusionsThe research has for the first time proved that this A. woluwensis TDS9 strain can efficiently convert cellulose. Therefore, the strain TDS9 could be a potential candidate for cellulase production in an industrial biotransformation process of paper mill sludge to produce reducing sugar. This sugar stream can be further used as a substrate to produce biofuels and other organic acids using another microorganism, which represents a greener alternative to add value to the paper production helping paper mill industries.

Project description:Lignin is a recalcitrant macromolecule formed by three alcohols (monolignols) predominantly connected by β-aryl ether linkages and is one of the most abundant organic macromolecules in the biosphere. However, the role played by environmental bacteria in lignin degradation is still not entirely understood. In this study, we identified an environmental Klebsiella strain isolated from sediment collected from an altitudinal region in a unique Brazilian biome called Caatinga. This organism can also grow in the presence of kraft lignin as a sole source of carbon and aromatic compounds. We performed whole-genome sequencing and conducted an extensive genome-based metabolic reconstruction to reveal the potential mechanisms used by the bacterium Klebsiella variicola P1CD1 for lignin utilization as a carbon source. We identified 262 genes associated with lignin-modifying enzymes (LMEs) and lignin-degrading auxiliary enzymes (LDAs) required for lignin and aromatic compound degradation. The presence of one DyP (Dye-decolorizing Peroxidase) gene suggests the ability of P1CD1 strain to access phenolic and nonphenolic structures of lignin molecules, resulting in the production of catechol and protocatechuate (via vanillin or syringate) along the peripheral pathways of lignin degradation. K. variicola P1CD1 uses aldehyde-alcohol dehydrogenase to perform direct conversion of vanillin to protocatechol. The upper funneling pathways are linked to the central pathways of the protocatechuate/catechol catabolic branches via β-ketoadipate pathways, connecting the more abundant catabolized aromatic compounds with essential cellular functions, such as energy cellular and biomass production (i.e., via acetyl-CoA formation). The combination of phenotypic and genomic approaches revealed the potential dissimilatory and assimilatory ability of K. variicola P1CD1 to perform base-catalyzed lignin degradation, acting on high- and low-molecular-weight lignin fragments. These findings will be relevant for developing metabolic models to predict the ligninolytic mechanism used by environmental bacteria and shedding light on the flux of carbon in the soil.

Project description:Lignin is a complex natural organic polymer and is one of the primary components of lignocellulose. The efficient utilization of lignocellulose is limited because it is difficult to degrade lignin. In this study, we screened a lacz1 gene fragment encoding laccase from the macrotranscriptome data of a microbial consortium WSC-6, which can efficiently degrade lignocellulose. The reverse transcription-quantitative PCR (RT-qPCR) results demonstrated that the expression level of the lacz1 gene during the peak period of lignocellulose degradation by WSC-6 increased by 30.63 times compared to the initial degradation period. Phylogenetic tree analysis demonstrated that the complete lacz1 gene is derived from a Bacillus sp. and encoded laccase. The corresponding protein, LacZ1, was expressed and purified by Ni-chelating affinity chromatography. The optimum temperature was 75°C, the optimum pH was 4.5, and the highest enzyme activity reached 16.39 U/mg. We found that Cu2+ was an important cofactor needed for LacZ1 to have enzyme activity. The molecular weight distribution of lignin was determined by gel permeation chromatography (GPC), and changes in the lignin structure were determined by 1H nuclear magnetic resonance (1H NMR) spectra. The degradation products of lignin by LacZ1 were determined by gas chromatography and mass spectrometry (GC-MS), and three lignin degradation pathways (the gentian acid pathway, benzoic acid pathway, and protocatechuic acid pathway) were proposed. This study provides insight into the degradation of lignin and new insights into high-temperature bacterial laccase. IMPORTANCE Lignin is a natural aromatic polymer that is not easily degraded, hindering the efficient use of lignocellulose-rich biomass resources, such as straw. Biodegradation is a method of decomposing lignin that has recently received increasing attention. In this study, we screened a gene encoding laccase from the lignocellulose-degrading microbial consortium WSC-6, purified the corresponding protein LacZ1, characterized the enzymatic properties of laccase LacZ1, and speculated that the degradation pathway of LacZ1 degrades lignin. This study identified a new, high-temperature bacterial laccase that can degrade lignin, providing insight into lignin degradation by this laccase.

Dataset Information

Isolation of functional ligninolytic Bacillus aryabhattai from paper mill sludge and its lignin degradation potential.

Publications

Isolation of functional ligninolytic <i>Bacillus aryabhattai</i> from paper mill sludge and its lignin degradation potential.

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