Genome shuffling to improve fermentation properties of top-fermenting yeast by the improvement of stress tolerance

Abstract

Fermentation properties of top-fermenting yeast are under the control of multiple genes difficult to manipulate directly by classical breeding, metabolic engineering, or other genetic methods with specific genes or pathways as target. Here, genome shuffling is introduced to improve fermentation performance (such as the viability of the yeast, flavor of beer, and the fermentation time) by improving wort and ethanol tolerance of top-fermenting yeast. The strategy was performed not based on polyethylene glycol (PEG)-mediated protoplast fusion but using yeast sexual and asexual reproduction by itself. The best performing strain W3-8 was selected on the selective plates after 3 rounds of genome shuffling. The fermentation time of W3-8 was not only markedly shortened, but also, most flavor compounds were distinctly improved. In particular, ethanol yield was increased by up to 67% after the 3rd pitching compared with the control. Furthermore, W3-8 promoted desired amounts of esters and higher alcohols, in accordance with specific consumer preferences. Significant improvement in the fermentation traits of the top-fermenting yeast was achieved using genome shuffling.