A Thermophilic GH5 Endoglucanase from Aspergillus fumigatus and Its Synergistic Hydrolysis of Mannan-Containing Polysaccharides

In this study, we isolated and identified a thermophilic strain of Aspergillus fumigatus from the Daqu samples. Transcriptomic analysis of A. fumigatus identified 239 carbohydrate-active enzymes (CAZy)-encoding genes, including 167 glycoside hydrolase (GH)-encoding genes, 58 glycosyltransferase (GT)-encoding genes, 2 polysaccharide lyase (PLs)-encoding genes and 12 carbohydrate esterase (CEs)-encoding genes, which indicates that the strain has a strong potential for application for enzyme production. Furthermore, we also identified a novel endoglucanase gene (AfCel5A), which was expressed in Pichia pastoris and characterized. The novel endoglucanase AfCel5A exhibited the highest hydrolytic activity against CMC-Na and the optimal activity at 80 degrees C and pH 4.0 and also showed good stability at pH 3.0-11.0 and below 70 degrees C. The Km and Vmax values of AfCel5 were 0.16 +/- 0.05 mg center dot mL(-1) and 7.23 +/- 0.33 mol mg(-1)center dot min(-1), respectively, using CMC-Na as a substrate. Further, the endoglucanase exhibited a high tolerance toward NaCl as well as glucose. In addition, the finding that the endoglucanase AfCel5A in combination with beta-mannanse (ManBK) clearly increased the release of total reducing sugars of glucomannan by up to 74% is significant.

Automated summary

The study isolated a thermophilic strain of Aspergillus fumigatus with potential for enzyme production, including a novel endoglucanase (AfCel5A) characterized for its high hydrolytic activity against CMC-Na. AfCel5A exhibited optimal activity at 80 degrees C and pH 4.0, with good stability across a wide pH range and temperature. It also showed increased total reducing sugar release in combination with beta-mannanse (ManBK).