Synergistic enhancement of PBAT biodegradation by Purpureocillium lilacinum BA1S: Insights from transcriptomics and functional analyses.

Poly (butylene adipate-co-terephthalate) (PBAT) is a biodegradable polyester widely used in agriculture and packaging. However, its slow decomposition under natural conditions raises environmental concerns. In this study, we explored strategies to enhance PBAT degradation by Purpureocillium lilacinum strain BA1S. A synergistic effect was identified through the combined application of calcium salt supplementation and mildly alkaline conditions (pH 7.5), resulting in a significant improvement in PBAT degradation, with 54.72 wt% film loss within 14 days. Physicochemical analyses revealed distinct surface erosion patterns and altered hydrolytic product distribution under these conditions. Transcriptomic and gene correlation network analyses identified a suite of differentially expressed genes involved in depolymerization, biosurfactant production, membrane transport systems, and metabolic processing. Under co-stimulatory conditions, TCA cycle-related genes were downregulated, while those involved in proteolysis, membrane transport, endocytosis, and biosurfactant synthesis were upregulated. Correspondingly, functional assays confirmed that biosurfactant activity was enhanced under these treatments. Moreover, calcium ions improved the thermostability of recombinant BA1S cutinase (PlCut), reducing its thermal inactivation. Taken together, these findings elucidate a multi-layered mechanism by which BA1S degrades PBAT and highlight how environmental factors can modulate fungal plastic degradation. This study sheds new light on microbial PBAT degradation and offers promising strategies toward sustainable applications.