Direct Conversion of Cellulose into Ethanol and Ethyl-..beta..-d-Glucoside via Engineered Saccharomyces cerevisiae

Simultaneous saccharification and fermentation (SSF) of cellulose via engineered Saccharomyces cerevisiae is a sustainable solution to valorize cellulose into fuels and chemicals. In this study, we demonstrate the feasibility of direct conversion of cellulose into ethanol and a bio-degradable surfactant, ethyl-..beta..-d-glucoside, via an engineered yeast strain (i.e., strain EJ2) expressing heterologous cellodextrin transporter (CDT-1) and intracellular ..beta..-glucosidase (GH1-1) originating from Neurospora crassa. We identified the formation of ethyl-..beta..-d-glucoside in SSF of cellulose by the EJ2 strain owing to transglycosylation activity of GH1-1. The EJ2 strain coproduced 0.34 +/- 0.03 g ethanol/g cellulose and 0.06 +/- 0.00 g ethyl-..beta..-d-glucoside/g cellulose at a rate of 0.30 +/- 0.02 g/L/h and 0.09 +/- 01 g/L/h, respectively, during the SSF of Avicel PH-101 cellulose, supplemented only with Celluclast 1.5L. Herein, we report a possible co-production of a value-added chemical (alkyl-glucosides) during SSF of cellulose exploiting the transglycosylation activity of GH1-1 in engineered S. cerevisiae. This co-production could have a substantial effect on overall techno-economic feasibility of SSF of cellulose.