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

[Display omitted] • Low temperature severely limits rice straw-silage processing. • Novel cold-active cellobiohydrolase Vv CBHI-I from V. volvacea was isolated. • Vv CBHI-I exhibited outstanding cellobiohydrolase activity at 10–30 °C. • Vv CBHI-I greatly improved saccharification efficiency of cellulase complex at 10 °C. • A flexible structure and fewer disulfide bonds explain Vv CBHI-I cold acclimation. 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 (Vv CBHI-I) was isolated from Volvariella volvacea , which exhibited outstanding cellobiohydrolase activity at 10–30 °C. The crude cellulase complex in the Vv CBHI-I-expressing transformant T1 retained 50% relative activity at 10 °C, while the wildtype Trichoderma reesei showed <5% of the activity. Vv CBHI-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% ± 0.15% and 21.25% ± 0.26% of the dried material. This demonstrates the crucial potential of mushroom-derived cold-active cellobiohydrolases in successful ensiling in cold regions. [ABSTRACT FROM AUTHOR]