Abstract: In this study, a thermophilic fungus, designated GZFH7, that can produce thermophilic mannanase was isolated from Maotai-flavor Daqu, a traditional fermentation starter for the production of Maotai-flavor Baijiu. The fungus was identified as Rhizomucor pusillus, and the optimal reaction temperature of mannanase produced from konjac gum by this strain was 70 ℃. At temperatures ranging from 50 to 80 ℃, the enzyme retained more than 50% of its activity, and kept its activity almost unchanged for 1 h at the optimal reaction temperature. The optimal reaction pH of the enzyme was 5.0, and it was tolerant to pH 2.0 to 12.0. Transcriptomic analysis showed that 253 carbohydrate-active enzymes (CAZyme) genes such as chitinase, galactosidase, and mannosyltransferase were expressed. Among them, glycosyltransferase was most abundantly expressed, accounting for 41.1% of the total, followed by glycoside hydrolase, about 37.5%. The mannanase produced by R. pusillus GZFH7 had good thermal stability. Furthermore, this strain could efficiently produce CAZymes, proving its great potential for the development and application of enzyme preparations.

Key words: β-1,4-D-mannanase; thermophilic enzyme; transcriptomics; carbohydrate-active enzymes; Rhizomucor pusillus