L-rhamnose enhances oxidative stress tolerance and biological control efficacy in Pichia kudriavzevii.

Abstract

Antagonistic yeasts are promising biocontrol agents for postharvest disease management; however, their efficacy is often constrained by limited stress tolerance in fruit wound microenvironments. This study investigated whether L-rhamnose could improve the antagonistic activity of Pichia kudriavzevii K210607D against Alternaria tenuissima, and explored the associated metabolic and antioxidant responses. Growth analysis indicated that L-rhamnose supplementation slightly promoted the proliferation of P. kudriavzevii. Among the tested treatments, supplementation with 0.5% (w/v) L-rhamnose for 36 h exhibited the strongest inhibitory effect against A. tenuissima, with an approximately 15% increase in inhibition rate compared with the non-induced yeast in vitro. L-rhamnose treatment increased glucose-6-phosphate dehydrogenase (G6PDH) activity and the NADPH/NADP+ ratio in P. kudriavzevii, suggesting that pentose phosphate pathway (PPP)-associated metabolism was enhanced. Under H2O2 stress, L-rhamnose-treated cells showed greater apparent tolerance to oxidative stress, lower intracellular reactive oxygen species (ROS) accumulation, enhanced catalase (CAT) and superoxide dismutase (SOD) activities, and elevated expression of ZWF1, GLR1, CAT1, and SOD1. In vivo assays further demonstrated that 0.5% (w/v) L-rhamnose-induced P. kudriavzevii reduced lesion development on inoculated crabapple fruit by 77% compared with sterile distilled water treatment. These findings suggest that L-rhamnose treatment can improve the oxidative stress tolerance and biocontrol performance of P. kudriavzevii, providing a potential approach for improving antagonistic yeast efficacy.