Economic production of thermo-active endo β-mannanase for the removal of food stain and production of antioxidant manno-oligosaccharides

Abstract

β-Mannanases are β-1,4-mannan-glycosidic bonds hydrolyzing enzymes that participate in various biotechnological applications. In the current study, the production of the enzyme was performed by solid state fermentation of rice straw using the locally isolated fungus Trichoderma longibrachiatum RS1 and the production of the enzyme was optimized to reach 89.73U/g dry substrate. The isolated fungus was identified on the base of its cultural and morphological features and by 18S rDNA sequencing.The optimum temperature for the activity of the partially purified enzyme was indicated to be 75 °C. Although production of fungal β-mannanases have been previously studied but the production of thermo-active enzymes are still challengeable. The Vmax and Km were 6.2U/mg protein/min and 3.33 mg/mL respectively, indicating the comparatively high affinity of the produced enzyme toward mannan substrates. The thermal stability of the produced enzyme estimated that its half lives were 633.01, 50.77 and 20.25 min−1 at 55, 60 and 65 °C respectively. The produced enzyme can be efficiently used in the removal of mannan based food stain. Moreover, the efficiency of the produced enzyme in the production of manno-oligosaccharides by the hydrolysis of mannan polymers was examined. The results indicated the release of 1.8 and 0.66 mg reducing sugar/mL by the hydrolysis of locust bean and guar gum for 2 h with hydrolysis percentage of 27 and 9.9% respectively. Finally, the produced manno-oligosaccharides were examined for their antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl free radical.