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An alkaline-thermostable mannanase from Streptomyces sp. CS428 was produced, purified, and biochemically characterized. The extracellular mannanase (Mn428) was purified to homogeneity with 12.4 fold, specific activity of 2406.7 U/mg, and final recovery of 37.6 %. The purified β-mannanase was found to be a monomeric protein with a molecular mass of approximately 35 kDa as analyzed by SDS-PAGE and zymography. The first N-terminal amino acid sequences of mannanase enzyme were HIRNGNHQLPTG. The optimal temperature and pH for enzyme were 60 °C and 12.5, respectively. The mannanase activities were significantly affected by the presence of metal ions, modulators, and detergents. Km and Vmax values of Mn428 were 1.01 ± 3.4 mg/mL and 5029 ± 85 µmol/min mg, respectively when different concentrations (0.6-10 mg/mL) of locust bean gum galactomannan were used as substrate. The substrate specificity of enzyme showed its highest specificity towards galactomannan which was further hydrolyzed to produce mannose, mannobiose, mannotriose, and a series of mannooligosaccharides. Mannooligosaccharides can be further converted to ethanol production, thus the purified β-mannanase isolated from Streptomyces sp. CS428 was found to be attractive for biotechnological applications.

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A novel, low-molecular weight, alkaline mannanase from Streptomyces tendae (MnSt) was purified to homogeneity and biochemically characterized. The extracellular mannanase was purified with 26.3% yield using a Sepharose Cl-6B column. The molecular mass of MnSt was approximately 24 kDa. MnSt was stable over a broad pH range (5 ~ 12.5), was thermally stable at 60°C, and functioned optimally at 50°C and a pH of 12.0. MnSt had K m and V max values of 0.05 ± 1 mg/mL and 439 ± 0.5 mmol/min, respectively, using bean gum galactomannan as a substrate. The N-terminal sequence of MnSt was GWSVDAPYIAXQPFS. Thin layer chromatography (TLC) analysis of the MnSt hydrolysis products suggested that the major oligosaccharide produced was mannobiose. MnSt activity was remarkably affected by metal ions, modulators, chelators, and detergents. MnSt was simple to purify, had high thermal stability, was stable over a broad pH range, and produced mannooligosaccharides. MnSt has high potential for use as an industrial biocatalyst, particularly as a bio-bleaching agent or for oligosaccharide production.