Unveiling a novel Neobacillus strain: Optimization, metabolomic, and genomic insights into polyvinyl chloride microplastic biodegradation

Abstract

Polyvinyl chloride microplastics (PVC-MPs) are persistent environmental contaminants requiring effective remediation strategies. This study investigated microbial-mediated biodegradation by isolating bacteria from landfill soil samples with prolonged plastic waste exposure. PVC microplastics (Mn ≈ 35,000 g/mol, Mw ≈ 62,000 g/mol) were used as the substrate. Two microbial consortia, CPVC-KKU2 and CPVC-KKU6, demonstrated acid and lipase production capabilities. Subsequent isolation yielded five bacterial strains, with Bacillus sp. PVCKKU2 and Neobacillus sp. PVCKKU3 exhibiting notable lipase activity. Under incubation conditions at 37 °C, PVCKKU2 and PVCKKU3 achieved 1.66 ± 0.17% and 7.04 ± 0.65% PVC-MP weight loss over 35 days, respectively, with PVCKKU3 demonstrating the highest degradation efficiency. Biochemical tests indicated nitrate reduction, arginine utilization, and glucose fermentation potential. FTIR revealed oxidative modifications, possible dechlorination, and polymer chain cleavage, while SEM confirmed surface deterioration. Response Surface Methodology (RSM) optimized conditions for PVC-MP biodegradation by PVCKKU3, predicting pH 7.7, ammonium nitrate 1.3 g/L, and PVC-MP 0.92% (w/v), resulting in 7.65% predicted degradation, validated experimentally at 8.07%. LC-MS metabolomic analysis revealed notable modulation of amino acid metabolism, TCA cycle intermediates, and glutathione pathways, with detection of key aliphatic and aromatic degradation intermediates. Whole-genome sequencing of PVCKKU3 revealed a genome size of 5.91 Mbp containing seven putative biosynthetic gene clusters. Comparative genomic analysis identified 12 unique gene clusters predicted to be associated with PVC degradation. These findings establish Neobacillus sp. PVCKKU3 as a promising candidate for PVC-MP bioremediation and provide genomic foundations for future enzyme-based remediation strategies.