EngineeringPichia pastoriswith surface-display minicellulosomes for carboxymethyl cellulose hydrolysis and ethanol production

Backgrounds Engineering yeast as a consolidated bioprocessing (CBP) microorganism by surface assembly of cellulosomes has been aggressively utilized for cellulosic ethanol production. However, most of the previous studies focused onSaccharomyces cerevisiae, achieving efficient conversion of phosphoric acid-swollen cellulose (PASC) or microcrystalline cellulose (Avicel) but not carboxymethyl cellulose (CMC) to ethanol, with an average titer below 2 g/L. Results Harnessing an ultra-high-affinity IM7/CL7 protein pair, here we describe a method to engineerPichia pastoriswith minicellulosomes by in vitro assembly of three recombinant cellulases including an endoglucanase (EG), an exoglucanase (CBH) and a beta-glucosidase (BGL), as well as a carbohydrate-binding module (CBM) on the cell surface. For the first time, the engineered yeasts enable efficient and direct conversion of CMC to bioethanol, observing an impressive ethanol titer of 5.1 g/L. Conclusions The research promotes the application ofP. pastorisas a CBP cell factory in cellulosic ethanol production and provides a promising platform for screening the cellulases from different species to construct surface-assembly celluosome.