Engineering Pichia pastoris with surface-display minicellulosome for carboxymethyl cellulose hydrolysis and ethanol production

Abstract

Backgrounds: Engineering yeast with cell surface immobilized cellulosome is a promising strategy for consolidated bioprocessing (CBP) to produce bioethanol from the conversion of cellulose. However, previous studies mostly focused on utilization of Saccharomyces cerevisiae , which was able to directly convert 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 engineer Pichia pastoris with minicellulosome through in vitro assembly of various recombinant cellulases on the cell surface. For the first time, the yeast can efficiently convert CMC to bioethanol, achieving an impressive ethanol titer of 5.1 g/L. Further, the engineered yeasts were lyophilized to powders that can be utilized as compound cellulases. Conclusions: This research promotes the application of P. pastoris as CBP cell factory in cellulosic ethanol production and provides a promising platform for screening optimal cellulase species and ratios to construct celluosome on the yeast cell surface.