Rational strain engineering interventions to enhance cellulase secretion by Saccharomyces cerevisiae

Abstract

AbstractLignocellulosic biomass remains an attractive feedstock for the production of fuels if a technology can be developed to overcome its recalcitrance. Consolidated bioprocessing (CBP) is one technology under development that aims to make this conversion process economically feasible. While no ideal CBP organism has been developed, several options have been pursued including engineering of the ethanologenic yeast Saccharomyces cerevisiae. Considering the genetic malleability of this model organism, a variety of chemicals and chemical precursors could also be produced directly from cellulosic feedstocks, assuming an enzymatic system for the hydrolysis of the feedstock sugar polymers can be established. While there have been several accounts of the secretion of cellulases by strains of S. cerevisiae and the successful conversion of limited amounts of amorphous and model crystalline cellulose feedstocks to ethanol, substantial conversion of crystalline cellulose by these strains in the absence of exogenous cellulases has not been reported. The most cited reasons for this were the low secretion titer of cellulases in general and of cellobiohydrolases in particular. This review will compare the efforts that have been made to enhance heterologous protein secretion in the yeast S. cerevisiae through rational strain engineering with a focus on cellulases and will investigate important factors in developing successful CBP‐yeast strains. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd