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

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 similar to 45 kDa. The rMtCel6A is active in a wide range of pH (4-12) and temperatures (40-100 degrees C) with optima at pH 10.0 and 60 degrees C. It exhibits T-1/2 of 6.0 and 1.0 h at 60 and 90 degrees 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 mu mol 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.

Automated summary

The study successfully cloned and expressed a codon optimized cellobiohydrolase gene from Myceliophthora thermophila in Escherichia coli, demonstrating excellent properties such as stability and tolerance to various environmental conditions. The recombinant MtCel6A is a potential CBH enzyme for industrial applications.