Genetic Modification of Yarrowia lipolytica for Consolidated Bioprocessing of Biofuels

Yarrowia lipolytica, a species of yeast, is capable of converting glucose into lipids. However, it lacks the enzymes to break down cellulose and cannot utilize biomass directly. The potential of Y. lipolytica as a bioprocessing strain was investigated by the team of Hui Wei, Wei Wang and Min Zhang from National Renewable Energy Laboratory in the United States. The team engineered critical cellulases from Trichoderma reesei into Yarrowia for it to function as a consolidated bioprocessing strain.

Yarrowia expressed T. reesei endoglucanase II (EGII) and cellobiohydrolase (CBH) II. However, the cellulase T. reesei CBHI was found incompatible to Yarrowia. This forced them to evaluate alternative CBHI enzymes. Among the enzymes evaluated, the T. reesei-Talaromyces emersonii (Tr-Te) chimeric CBHI showed activity comparable to T. reesei CBHI. It also showed synergism with EGII and CBHII in degrading cellulosic substrates.

This study shows the first case of successful expression of a chimeric CBHI in Y. lipolytica, and proves that Y. lipolytica can be genetically engineered to directly convert lignocellulosic substrates to biofuels.