Evaluation of the effect of molecular weight change of konjac glucomannan on antioxidant and tyrosinase activities

Abstract

The purpose of this study was to characterize the biological activity of konjac glucomannan (KGM) according to its molecular weight change. KGM-degrading bacterial strain, N3 was isolated from soil and named Bacillus aerophilus following 16S rDNA sequencing and homology analysis. KGMase, a thermophilic konjac glucomannan-degrading enzyme, was partially purified by treating the culture supernatant of strain B. aerophilus N3 with 50% ammonium sulfate followed by rigorous heating at 75 degrees C for 30 min. The molecular weight (MW) of KGMase was determined to be approximately 41,000 by silver staining following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The biochemical properties stipulated that KGMase is optimally active at 45 degrees C and pH 6.5 which shows the high temperature and pH stability of KGMase. Manno-oligosaccharides (MOs) derived from the hydrolysis of KGM by KGMase showed a concentration-dependent increase in tyrosinase activity. MOs are bioactive compounds derived from the hydrolysis of KGM by the thermophilic KGMase of B. aerophilus and the outcomes of our study demonstrated that MOs will be suitable for application in the cosmetics industry.