Thermostability modification of a deoxynivalenol-degrading enzyme from Pelagibacterium nitratireducens ZH15, a bacterium screened using a novel dehydrogenase activity-based method

The cascade catalysis of deoxynivalenol (DON) by dehydrogenases and aldo/keto reductases from bacteria is an eco-friendly detoxification strategy. However, the instability of most reported first-step DON-degrading enzymes limits their practical applications. In this study, a strain Pelagibacterium nitratireducens ZH15 with high DON degradation ability was obtained using a novel dehydrogenase activity-based screening method. One dehydrogenase ZHDDH4 capable of DON ketonization and one aldo/keto reductase ZHAKR8 capable of 3-keto-DON reduction were identified from P. nitratireducens ZH15. M526E, the single mutant of ZHDDH4 constructed in the current study, could completely degrade 50 μg/mL DON in 48 h with PQQ as the hydrogen acceptor, and ZHAKR8 could degrade 73.12 % of 30 μg/mL 3-keto-DON in 2 h with NADPH as the cofactor. Subsequently, structure-based and computer-aided engineering was implemented to improve the thermostability of dehydrogenase M526E. Through this strategy, the best double mutant M526E/N105M showed enhanced thermostability with 59.87 % and 10.62 % of DON removal ratio after being incubated at 60 and 70 °C for 1 h, respectively. M526E/N105M can also degrade 15-acetyl-DON and nivalenol. M526E/N105M will be appropriate for the practical applications of DON and its derivatives detoxification because of its high activity and thermostability. Collectively, the simple and effective strategies for mining novel microorganisms and enhancing the thermostability of DON-degrading enzymes in the current study enrich the research on DON and its derivatives decontamination.