Preparation of mid-to-high molecular weight konjac glucomannan (MHKGM) using controllable enzyme-catalyzed degradation and investigation of MHKGM properties

Mid-to-high molecular weight konjac glucomannan (MHKGM) powders with different molecular weights were prepared and purified from their enzymatic hydrolysis solutions. MHKGM powder yield was optimized with respect to substrate concentration, urea concentration, the number of alcohol washings, and drying temperature. Properties of MHKGM powder were characterized by SEC, FTIR, UV, XRD, rheological, and thermal analysis techniques. The results showed that under the correct conditions a high productive yield of MHKGM can be obtained. MHKGMs have the same chemical structure as that of native KGM, but their weight average molecular weight (M _w), molecular weight distribution index (M _w/M _n), radius of gyration (R _g), solution optical clarity, rheological properties, and other physical properties such as water solubility are very different from those of native KGM. This study provides useful a reference for making MHKGM powder with varying molecular weight and the potential applications of KGM such as healthy food additives.