Recombinant cellobiohydrolase of Myceliophthora thermophila: characterization and applicability in cellulose saccharification

Abstract

Abstract A codon optimized cellobiohydrolase (CBH) encoding synthetic gene of 1188 bp from a thermophilic mold Myceliophthora thermophila ( MtCel6A ) was cloned and heterologously expressed in Escherichia coli for the first time. In silico analysis suggested that MtCel6A is a GH6 CBH and belongs to CBHII family, which is structurally similar to Cel6A of Humicola insolens . The recombinant MtCel6A is expressed as active inclusion bodies, and the molecular mass of the purified enzyme is ~ 45 kDa. The rMtCel6A is active in a wide range of pH (4–12) and temperatures (40–100 °C) with optima at pH 10.0 and 60 °C. It exhibits T 1/2 of 6.0 and 1.0 h at 60 and 90 °C, respectively. The rMtCel6A is an extremozyme with organic solvent, salt and alkali tolerance. The K m , V max , k cat and k cat /K m values of the enzyme are 3.2 mg mL −1 , 222.2 μmol mg −1 min −1 , 2492 s −1 and 778.7 s −1 mg −1 mL −1 , respectively. The product analysis of rMtCel6A confirmed that it is an exoenzyme that acts from the non-reducing end of cellulose. The addition of rMtCel6A to the commercial cellulase mix (Cellic CTec2) led to 1.9-fold increase in saccharification of the pre-treated sugarcane bagasse. The rMtCel6A is a potential CBH that finds utility in industrial processes such as in bioethanol, paper pulp and textile industries. Graphical Abstract

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