Novel genetic parts and cultivation strategies for yeast-based conversion of lignocellulosic feedstocks

The recent start-up of several full-scale ‘second generation’ ethanol plants marks a major milestone in the development of Saccharomyces cerevisiae yeast strains for fermentation of lignocellulosic hydrolysates of agricultural residues and energy crops. In contrast to the fermentation of hexose sugar-rich substrates, such as corn syrup or sugar cane bagasse, these hydrolysates contain mixtures of the hexose sugar D-glucose and the pentose sugars D-xylose and L-arabinose. While S. cerevisiae performs excellently in fermenting hexose sugars to ethanol, efficient utilization of pentose sugars required extensive metabolic and evolutionary engineering.