Manno‐oligosaccharide preparation by the hydrolysis of konjac flour with a thermostable endo‐mannanase from Talaromyces cellulolyticus

Abstract

A thermostable endo-mannanase from the fungus Talaromyces cellulolyticus was identified to facilitate manno-oligosaccharide preparation from Konjac (Amorphophallus konjac) flour. A putative endo-1,4-β-mannanase from the T. cellulolyticus was obtained and efficiently expressed by improving its gene dosage in the genome of the host. After cultivation in a bench-top bioreactor for about 120h, the protein content and enzyme activity of mannanase increased to 3·4gl-1 and 17500Uml-1 respectively. Enzymatic characterization showed that this enzyme has an optimal temperature of 80°C, optimal pH of 5·0. Under the optimized hydrolysis conditions of pH 5·0, 70°C, and an enzyme concentration of 200Ul-1 solution, this enzyme could efficiently hydrolyse 0·5% konjac flour into manno-oligosaccharides (MOSs) with the degree of polymerization range from 3 to 7. The possible mechanism by which the enzyme produced MOSs was also discussed. Talaromyces cellulolyticus endo-mannanase is thermostable and has a broad pH range adaptability. Method of improving the dosage of mannanase gene in the genome could realized its high-level impression. This enzyme could efficiently hydrolyse konjac flour into manno-oligosaccharide products. This study has enriched endo-mannanase resources, facilitated its bulk production and provided a strong reference for its application in manno-oligosaccharide preparation from the natural glucomannan of konjac flour.