Biodegradation of polystyrene and its mechanisms driven by a customized lignin-degrading microbial consortium and degrading bacteria

Polystyrene (PS), being resistant to biodegradation, poses a significant environmental challenge. This study isolated highly effective lignin-degrading microbial consortia from samples collected at six sites rich in lignin-degrading bacteria. After 360 days of enrichment, a stable lignin-degrading microbial consortium, LQX-03, was successfully established. LQX-03 demonstrated notable degradation efficiency not only for lignin (21-day degradation rate of 54.6 %) but also for PS (21-day degradation rate of 13.1 %). Importantly, PS-induced LQX-03 communities overlapped with the original lignin communities in 13 genera, revealing a close relationship between the degrading microbial compositions of the two substrates.Additionally, Pseudomonas putida Q1, isolated from LQX-03, exhibited significant capability in simultaneously degrading lignin and PS, achieving degradation rates of 36.1 % and 4.4 %, respectively. The strain was also able to alter the functional groups of PS, increasing its hydrophilicity. Gene and enzyme expression analyses revealed that key lignin-degrading enzymes, such as laccase (CopA) and DyP peroxidase, were significantly upregulated when PS was the sole substrate. Laccase CopA expression increased by 1.76-fold and 1.41-fold, while DyP expression increased by 1.24-fold. These results indicate that these enzymes likely play a crucial role in PS depolymerization and biodegradation. Further molecular docking analysis confirmed that laccase CopA could bind to PS. In summary, this study provides preliminary insights into the potential links between lignin-degrading and plastic-degrading microorganisms and their enzymes. It suggests that the biodegradation of synthetic plastics may rely on ancient natural lignin-degrading enzymes. These findings offer a new perspective and valuable data for developing efficient plastic biodegradation strategies.