Partial purification and application of β-mannanase for the preparation of low molecular weight galacto and glucomannan

Abstract

The newly isolated Streptomyces sp. RDA1496 produced high activity of β-mannanase (415.96 IU/mL) when grown on optimized medium conditions. The produced enzyme was purified to partial homogeneity by ammonium sulphate precipitation followed by gel filtration. The β-mannanase was purified 5.12 fold to homogeneity with a specificity of 1118.79 IU/mg. The highly active fraction of β-mannanase from gel filtration, appeared as a protein band on SDS-PAGE gel with a molecular mass of 63.0 ± 2.0 kDa. β-mannanase was applied to prepare low molecular weight guar gum and konjac glucomannan by enzymatic de-polymerization. Gaur gum and konjac glucomannan (1.0% w/v) were hydrolyzed using the dialyzed β-mannanase, 3.0 mg/g of substrate for 24h. Molecular weight of hydrolyzed guar gum and konjac glucomannan were reduced to 40.73 kDa and 44.72 kDa. FTIR spectra of hydrolyzed mannan varied by different intensities of peaks compared to native mannan substrate and observed in vibrational area of O-H associated chemical group, –CH stretching of the –CH2 and –CH3 groups, and highly coupled C-C-O, C-OH and C-O-C of polymer backbone. Mannan substrates with lower molecular weight have great importance in nutrition and health industries, results indicate the hydrolyzed mannan substrates can be utilized as nutritional product for food industries.