Abstract

Pichia pastoris strain GS115 was engineered to express a synthetic gene encoding β-glucosidase for its use in ethanol production. β-glucosidase was expressed and secreted either as mature enzyme or N- hexahistidine (His6)-tagged fusion protein, under the control of the strong methanol inducible promoter AOX1. The recombinant β-glucosidase was partially characterized and showed properties comparable to native enzyme.  The transformed yeast acquired the ability to assimilate and ferment 1% cellobiose in non aerated batch cultures. Ethanol concentrations were 2.56 g/l and 1.35 g/l which corresponded to 84% and 45% for the non-His-tagged and His-tagged transformants respectively compared to glucose fermentation. A 2.4 fold increase in ethanol production was obtained upon methanol induction of yeast cells in the fermentation medium.

Key words: Pichia pastoris; Beta glucosidase; Gene cloning; Cellobiose; Submerged Fermentation; Ethanol.