Biodegradation of penicillin G sodium by Sphingobacterium sp. SQW1: Performance, degradation mechanism, and key enzymes

Biodegradation is an efficient and cost–effective approach to remove residual penicillin G sodium (PGNa) from the environment. In this study, the effective PGNa–degrading strain SQW1 (Sphingobacterium sp.) was screened from contaminated soil using enrichment technique. The effects of critical operational parameters on PGNa degradation by strain SQW1 were systematically investigated, and these parameters were optimized by response surface methodology to maximize PGNa degradation. Comparative experiments found the extracellular enzyme to completely degrade PGNa within 60 min. Combined with whole genome sequencing of strain SQW1 and LC–MS analysis of degradation products, penicillin acylase and β–lactamase were identified as critical enzymes for PGNa biodegradation. Moreover, three degradation pathways were postulated, including β–lactam hydrolysis, penicillin acylase hydrolysis, decarboxylation, desulfurization, demethylation, oxidative dehydrogenation, hydroxyl reduction, and demethylation reactions. The toxicity of PGNa biodegradation intermediates was assessed using paper diffusion method, ECOSAR, and TEST software, which showed that the biodegradation products had low toxicity. This study is the first to describe PGNa–degrading bacteria and detailed degradation mechanisms, which will provide new insights into the PGNa biodegradation. (a) Penicillin G sodium (PGNa) is a persistent compound with high concentrations in the PGNa fermentation fungi residues. Residual antibiotics cause great pollution to the environment, such as the production of antibiotic-resistant bacteria and resistance genes that are harmful to humans and animals. (b) In this study, a strain of Sphingobacterium sp. SQW1 was isolated and was able to efficiently degrade PGNa. This study suggests that SQW1 provides a bioremediation option for environments contaminated with PGNa and provides a reference for understanding the fate, transportation, and degradation of PGNa in the environment.