Degradation of konjac glucomannan by Thermobifida fusca thermostable β-mannanase from yeast transformant

Native konjac glucomannan was used as the substrate for thermophilic actinomycetes, Thermobifida fusca BCRC19214, to produce β-mannanase. The β-mannanase was purified and five internal amino acid sequences were determined by LC-MS/MS. These sequences had high homology with the β-mannanase from T. fusca YX. The tfm gene which encoded the β-mannanase was cloned, sequenced and heterologous expressed in Yarrowia lipolytica P01g expression system. Recombinant heterologous expression resulted in extracellular β-mannanase production at levels as high as 3.16 U/ml in the culture broth within 48 h cultivation. The recombinant β-mannanase from Y. lipolytica transformant had superior thermal property. The optimal temperature of the recombinant β-mannanase from Y. lipolytica transformant (pYLSC1-tfm) was 80 °C. When native konjac glucomannan was incubated with the recombinant β-mannanase from Y. lipolytica transformant (pYLSC1-tfm) at 50 °C, there was a fast decrease of viscosity happen during the initial phase of reaction. This viscosity reduction was accompanied by an increase of reducing sugars. The surface of konjac glucomannan film became smooth. After 24 h of treatment, the DPw of native konjac glucomannan decreased from 6,435,139 to 3089.