19446: C5/C6 Saccharomyces cerevisiae strains for bioconversion of lignocellulose

Lignocellulose raw materials are composed of lignin, cellulose and hemicellulose and require pre-treatment at elevated temperatures with acid or base to make cellulose and hemicellulose accessible to subsequent acid or enzymatic hydrolysis. During pre-treatment and hydrolysis fermentation inhibitors – phenol and furan derivatives and low molecular weight fatty acids - are released. Cellulose and hemicellulose are hydrolyzed to fermentable monomer C6 and C5 sugars (glucose, mannose, galactose, xylose and arabinose), while lignin may be recovered as fuel.

Hydrolyzed lignocellulose raw materials thus comprise a mixed-sugar substrate in an inhibiting matrix. The yeast Saccharomyces cerevisiae has been used throughout recorded human history to produce bread, beer, and wine and is currently the prime choice for industrial ethanol production. Previously, new yeast strains have been developed with recombinant DNA technology and metabolic engineering, usually in combination with random methods such as breeding, adaptation/evolutionary engineering and mutagenesis. In addition to rational design, inverse metabolic engineering as well as the concept of systems biology have made it possible to find unexpected engineering targets. Improved strains utilizing the pentose (C5) sugars xylose and arabinose have been developed as well as strains with improved inhibitor tolerance to be exploited in the future biofuels and biorefinery industries based on renewable lignocellulose raw materials.