Changes of the microbial community in kiwifruit during storage after postharvest application of Wickerhamomyces anomalus.

High-throughput sequencing techniques can provide important information for understanding the interaction between exogenous microbial agents and fruit microbial communities, and explain how it controls postharvest fungal diseases. In this study, we found that Wickerhamomyces anomalus could control the postharvest disease of kiwifruit. Meanwhile, high-throughput sequencing technology results showed that the composition and structure changes of the fungal community in microbial flora were significantly greater than those of bacteria after W. anomalus treated. W. anomalus could colonize inside the fruit and regulate the community composition of bacteria to reduce the abundance of pathogens and eventually maintain the healthy state of the fruit. The dominant genus in the microbiota of kiwifruit after application of W. anomalus showed an increased ability to interact. Some fungi or bacteria are positively associated with yeast in the epiphytic and endophytic sample communities, guiding the synthesis of compound biocontrol strains for kiwifruit postharvest diseases.

Effect of Rhodotorula mucilaginosa on patulin degradation and toxicity of degradation products.

Rhodotorula mucilaginosa is an antagonistic yeast for which our research team has recently reported interesting biocontrol activities against blue mould decay of apples and a strong ability to decrease the patulin concentration in vivo. However, the possible mechanisms of patulin degradation by R. mucilaginosa and the toxicity of patulin degradation products remain unclear. In this study, the effect of R. mucilaginosa on patulin degradation and toxicity of degradation products were investigated, the results showed that viable cells of R. mucilaginosa are essential to patulin degradation. Also, R. mucilaginosa eliminated patulin without adsorbing it through its cell wall. The extracellular metabolites of R. mucilaginosa stimulated by patulin showed little degradation activity for patulin. Cycloheximide addition into the medium significantly decreased the patulin degradation capacity of R. mucilaginosa cells. The main patulin degradation product by R. mucilaginosa was ascladiol, which was proved non-toxic to human hepatoma (HepG2) cells at 0.625-10 g/mL. Furthermore, toxicological analysis using a confocal laser scanning microscope revealed that the degradation product induced cellular apoptosis to a lesser extent than patulin itself. This result offers an innovative method to detoxify patulin and limit the risks of patulin in fruits and vegetables using R. mucilaginosa.