Ochratoxin A (OTA) poses a serious threat to human and animal health as well as the ecological environment due to its high toxicity, stable physicochemical properties, and widespread occurrence in food and feed. Because of their high efficiency, environmental friendliness and good specificity, biological enzymes have become an important research direction of OTA detoxification. This review systematically summarizes the OTA-degrading enzymes that have been reported, focusing on the strategies for optimizing their expression levels and enzymatic performance. The current research mainly focuses on carboxypeptidases and amidohydrolases, among which OTase and SaADH3 are representative in terms of their degradation efficiency and research depth. In view of the limited expression level and stability of natural OTA-degrading enzymes, the construction and optimization of efficient expression systems are crucial for their application. The expression level, catalytic activity, heat and acid tolerance of OTA-degrading enzymes can be significantly improved by gene element optimization, expression system selection, expression condition optimization, enzyme immobilization and rational design. Future research should further focus on the performance improvement and industrial application of OTA-degrading enzymes to promote their practical application in the field of food and feed safety.

Proteases have the advantages of high catalytic efficiency and strong specificity, which are widely used in food, chemical, medicine and other industrial fields. However, natural proteases are susceptible to environmental acidity and inappropriate environmental acidity reduces their catalytic efficiency. Effective strategies to improve the acidity resistance of enzymes are key to promote their industrial application. Rational design strategy is an effective technique to improve the acidic stability of enzymes, such as homologous sequence alignment, surface charge optimization, and intramolecular force optimization. Considering most foods and food raw materials which are subject to contamination by ochratoxin A (OTA) are acidic, this review summarizes the common strategies for improving the acidic stability of enzymes and their prospects for application in the field of OTA degradation. It is expected that this review will provide a reference for research on the acid resistance of industrial enzymes and provide a theoretical basis for the application of mycotoxin-degrading enzymes.

In order to investigate the structural composition and dynamics of culturable microbial community in chestnut fruits, the present study was conducted to collect live microorganisms from two chestnut samples (coded as H and D) stored at 25, 4 or −18 ℃ for different periods (0, 14 and 30 days). The live microbial diversity in chestnuts was investigated by Illumina MiSeq high-throughput sequencing. The results of macro-genome sequencing showed that in chestnuts, the dominant bacteria were Rahnella (32.02%), Serratia (25.39%), and Enterobacter (23.78%), and the dominant fungi were Candida (80.73%), Wickerhamomyces (8.10%), and Fusarium (5.06%). The results of plate identification revealed that Rahnella, Enterobacter, Pantoea, Candida and Fusarium were the dominant bacteria in chestnuts. Linear discriminant analysis effect size (LEfSe) analysis showed that the microbial community of chestnut samples stored at different temperatures for 30 days differed significantly at linear discriminant analysis (LDA) score > 2. The relative abundances of Brachybacterium, Penicillium, and Hanseniaspora were significantly higher in the samples stored at 25 ℃ than at 4 and −18 ℃. Scleroderma was dominant in chestnut at 4 ℃, and Leuconostoc, Metschnikowia, and Wickerhamomyces at −18 ℃. In summary, the findings of this study will provide a reference for the inhibition of harmful microorganisms and the utilization of beneficial microorganisms in chestnuts in the future.