Recombinant GH-26 endo-mannanase from Bacillus sp. CFR1601: Biochemical characterization and application in preparation of partially hydrolysed guar gum

Abstract

Biochemical characterization studies of ManB-1601, a recombinant endo-mannanase from Bacillus sp. CFR1601, revealed that the enzyme was optimally active at moderately high temperature (50–55 °C) and neutral pH (6–7). ManB-1601 showed excellent stability over a broad pH range of 6–10 by retaining more than 70% activity after 9 h of incubation at room temperature. The apparent Km, Vmax and Vmax/Km values of ManB-1601 were 6.5 mg/ml, 5000 IU/ml/min and 769.2 μmol/min/mg, respectively, using locust bean gum as the substrate. ManB-1601 was stable in the presence of organic solvents (DMSO, methanol, ethanol and acetone), heavy metals (Co2+, Ni2+, and Cu2+) and displayed tolerance towards proteases (trypsin and chymotrypsin). The hydrolysis of guar gum (GG) by ManB-1601 led to production of partially hydrolyzed guar gum (PHGG) with high flow behaviour index (1.478 PHGG, 0.332 GG), markedly reduced average degree of polymerization (14 PHGG, 890 GG), average molecular weight (3814 PHGG, 239883 GG), apparent viscosity (2.8 mPas PHGG, 346 mPa GG) and consistency index (0.2 mPasn PHGG, 5734.7 mPasn GG). FTIR spectra of GG and PHGG indicated no major functional group transformations and similarity in the basic chemical structure.