Recent strain and fermentation development for commercial ethanol production using xylose fermenting yeast

Terranol has developed a robust xylose fermenting yeast (Saccharomyces cerevisiae) for commercial production of lignocellulosic ethanol. By up-regulation of the pentose phosphate pathway, and expression of a bacterial xylose isomerase, as well as a xylose 1-epimerase, the strain utilizes an efficient metabolic pathway. All genes are stably integrated in the genome of the yeast. The strain has undergone extensive evolutionary engineering, resulting in rapid xylose consumption, very low xylitol formation, and high resistance towards inhibitors.

Terranol’s strain has repeatedly shown complete conversion of xylose and glucose in a short period of time in various lignocellulosic substrates. Ethanol yields above 90% within 48 hours have been shown both in-house as well as at different partners. Recent strain development has now resulted in a new strain version with higher tolerance towards various inhibitors, which in turn has resulted in significantly faster and more efficient fermentations.

Fast and efficient cell growth on e.g. molasses (or other industrially available media containing high concentrations of C6 sugars) in order to produce industrial quantities of yeast is important from an industrial and economical perspective. However, it is not trivial combining these traits with novel, high-performing recombinant C5-fermenting strains. Moreover, cell robustness and viability during storage is also critical for industrial feasibility. Hence, Terranol’s strains have been developed and selected for good propagation and formulation performance.

Furthermore, by combining high-performing strains with well-designed fermentations, continuous improvement of ethanol yields, productivities and/or titers have been obtained. The latest scientific results will be presented together with recent commercial progress.