Screening of Dominant Cellulose-Degrading Microbe in Humus and Optimisation of its Enzyme Producing Conditions and Application Optimization of Enzyme Production Conditions and Evaluation of Efficient Straw Degradation by Penicillium oxalicum

: The slow degradation of returned straw adversely affects seedling survival rate. To shorten the degradation time of lignin in maize straw in warm temperate regions, a cellulolytic microbial strain that can secrete polymer with high enzymatic activity was isolated from the humus, which helped to identify an effective strain to expedite the decomposition of returned maize straw. Using the molecular biology techniques of primary screening and re-screening using selective media, the dominant cellulolytic microbes in the humus were identified as Penicillium oxalicum ( P . oxalicum ) (KY781806.1). Inoculum size, initial pH, fermentation time, and temperature were optimized to increase cellulase activity. The activities of sodium Carboxymethyl Cellulose (CMC) and Filter Paper (FPA) were increased by 23.04 and 25.10%, respectively. The ability of P. oxalicum to utilize cellulose was also demonstrated using a filter paper degradation test and maize straw utilization experiment. Finally, the results of a field test showed that the addition of P . oxalicum X 5 caused the returned straw to degrade completely within 30 days.