Improving cold-adaptability of mesophilic cellulase complex with a novel mushroom cellobiohydrolase for efficient low-temperature ensiling

Low ambient temperature poses a challenge for rice straw-silage processing in cold climate regions, as cold limits enzyme and microbial activity in silages. Here, a novel cold-active cellobiohydrolase (VvCBHI-I) was isolated from Volvariella volvacea, which exhibited outstanding cellobiohydrolase activity at 10-30 degrees C. The crude cellulase complex in the VvCBHI-I-expressing transformant T1 retained 50% relative activity at 10 degrees C, while the wildtype Trichoderma reesei showed <5% of the activity. VvCBHI-I greatly improved the saccharification efficiency of the cellulase complex with pretreated rice straw as substrate at 10 C. In rice straw silage, pH (<4.5) and lactic acid content (>4.6%) remained stable after 15-day ensiling with the cellulase complex from T1 and Lactobacillus plantarum. Moreover, the proportions of cellulose and hemicellulose decreased to 29.84% & PLUSMN; 0.15% and 21.25% & PLUSMN; 0.26% of the dried material. This demonstrates the crucial potential of mushroom-derived cold active cellobiohydrolases in successful ensiling in cold regions.

Automated summary

A new cold-active cellobiohydrolase (VvCBHI-I) derived from Volvariella volvacea showed excellent activity at 10-30 degrees C, which enables efficient cellulose degradation and saccharification at low temperatures. The expression of VvCBHI-I in a transformant significantly improved the activity of cellulase at 10 degrees C, leading to stable silage fermentation with rice straw and reduction of cellulose and hemicellulose contents. These findings highlight the potential of mushroom-derived cold-active cellobiohydrolases in enhancing ensiling efficiency in cold climate regions.