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Isolation and mechanistic study of novel PLA-degrading bacteria from plastic manufacturing soil.
Summary
Scientists discovered two new soil bacteria that can break down PLA, a "compostable" plastic used in food packaging and utensils that actually takes a very long time to decompose in nature. The researchers pinpointed the specific enzymes these bacteria use to digest the plastic, which could help engineers develop faster, more efficient ways to break down plastic waste. This matters because reducing how long plastics linger in the environment means less plastic breaking down into the microplastics that end up in our water, food, and bodies.
Petroleum-derived plastic pollution has become increasingly severe, stimulating the application demand for biodegradable polylactic acid (PLA). Nevertheless, the slow natural degradation rate of PLA limits its large-scale practical application. In this study, two potential novel strains with PLLA-degrading capacity, Chryseobacterium sp. L42 and Pedobacter sp. D55, were successfully isolated based on microbial community analysis of soil from plastic-manufacturing plants, combined with transparent-circle assays and PLA-film degradation tests. Integrated transcriptomic analysis and RT-qPCR validation, together with functional verification via heterologous expression in E. coli BL21 (DE3), confirmed that enzymes 10_101 and 10_105 from strain L42 exhibit prominent PLA-degrading activity, and both possess dual esterase and protease activities. Results from AlphaFold3 protein-structure prediction and molecular docking revealed that these functional enzymes contain conserved active pockets of PHA depolymerase, which target the ester bonds of PLA trimers through hydrogen bonds and hydrophobic interactions. This study clarifies the multi-enzyme synergistic PLA-degradation pathway mediated by strain L42. It provides valuable novel bacterial strains and degrading enzymes for the efficient bioremediation of plastic waste, and offers theoretical basis and practical reference for overcoming the technical bottlenecks in PLA degradation.