Abstract
A β-mannanase-producing bacterial strain Bacillus circulans M-21 was isolated from soil. The strain grew well when mannan (konjac gum, guar gum or locust bean gum) was used as sole carbon source. The optimum fermentation conditions were determined as follows: 4 g/L guar gum as carbon source, 20 g/L soybean powder and 5 g/L (NH4)2HPO4 as nitrogen source, initial pH 8.0, and 32C. An extracellular β-mannanase was purified by anion-exchange chromatography on Q-Sepharose Fast Flow. The purified protein exhibited a single band on sodium dodecyl sulphate-polyacrylamide gel electrophoresis with a molecular mass of 33.4 kDa. Kinetic analysis showed that the enzyme exhibited the strongest binding affinity to konjac gum. The β-mannanase activity reached the maximum at 50C and pH 7.0, and was completely suppressed by Hg2+ and Ag+. The β-mannanase degrading products were mainly composed by disaccharide, trisaccharide and tetrasaccharide, which were all neutral hexose polymers. PRACTICAL APPLICATIONS Microbial β-mannanases are applied broadly in industrial processes, such as improving the quality of food and feed, biobleaching of softwood pulps in the paper and pulp industries, and reducing the viscosity of coffee extracts. They are also found application in oil drilling and detergent industry. β-Mannanase is an ideal tool for the preparation of manno-oligosaccharides, which have been proved to be excellent prebiotics stimulating growth of human-beneficial intestinal microflora. Potential applications of manno-oligosaccharides are found in foods, beverages and confectionary, especially in functional food additives. In the current study a β-1,4-mannanase was extracted and purified from Bacillus circulans M-21. The research results showed that this enzyme is suitable for the preparation of glucomanno- and galactomanno-oligosaccharide.
Published Version
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