Bio decomposition of paddy straw waste using laccase producing novel soil bacterial isolates: An eco-friendly and sustainable approach

The soil microbiome plays a pivotal role in carbon sequestration, particularly through the degradation of lignocellulosic biomass such as paddy straw, which is often disposed of through environmentally harmful practices like open-field burning. This study investigates the isolation and characterization of novel lignocellulolytic bacterial strains capable of efficiently degrading paddy straw, thereby contributing to sustainable carbon management. A diverse collection of 27 bacterial isolates was obtained from soil samples, demonstrating significant cellulase, laccase, and lignin-degrading activities. Detailed biochemical and phenotypic analyses revealed distinct metabolic profiles and carbon source utilization patterns among the isolates. Notably, strains SH2A, AK17, AK15, U6, and SH2 achieved up to 94% degradation of paddy straw within 25 days, with isolate GS5A exhibiting an 18% reduction in recalcitrant lignin content in paddy straw within just 10 days leading to enhanced bioavailability of structural polysaccharides, and accelerating microbial-mediated degradation processes. Enzyme kinetic studies indicated optimal laccase activity at temperatures of 45–55 °C and pH levels of 4–7, with isolates TR32, SH2A, and AK17 producing laccase activities exceeding 90 U/L. Molecular characterization via 16 S rRNA sequencing identified these isolates as belonging to genera such as Pseudomonas, Enterobacter, Acinetobacter, and Klebsiella, known for their lignocellulolytic enzyme production. The findings underscore the potential of these bacterial strains exhibiting rapid lignin degradation enabling faster and more effective paddy straw decomposition compared to previously reported strains. Thereby leading faster carbon sequestration through effective biomass management, contributing to the development of a circular bio-economy and sustainable agricultural practices.