ARF13 - Increased ethanol production by commercial yeast strains

Researcher:

Dr. George van der Merwe, Dept. of Molecular and Cell Biology, University of Guelph

Objectives:

1. To genetically alter commercial yeast strains by specifically deleing the VID28 gene.
2. To determine the suitability of commercial vid28 mutant strains for industrial fermentations by performing:
   • Fermentation analysis (strain viability and sugar-to-ethanol conversion rates)
   • Metabolite analyses (glucose utilization, ethanol production, organic acids and glycerol production)
   • Testing of yeast strain(s) in scale-up experiments.

Expected Benefits:

Increasing the efficiency and rate of yeast fermentation will produce ethanol more efficiently.  This project can benefit many industries, including yeast manufacturers and ethanol-producing industries dependent on yeast fermentations, and thereby benefit the economy of Ontario.

Summary of Research Results:

The development of strategies to increase the potential for generating alternative renewable energy sources is at the forefront of many research efforts internationally. With this funding we were able to demonstrate that the deletion of a specific gene, native to ethanol-producing yeast strains that potentially inhibit glucose metabolism, led to increased ethanol production by a commercial ethanol-producing yeast strain. We observed a 3.4 g/L increase in ethanol production from the glucose available to the genetically enhanced yeast when tested in laboratory conditions. This finding becomes significant when considering that one ethanol producing plant can produce 187 million litres of ethanol per year.

The genetically altered strain does not contain any antibiotic resistance genes and no new genes were introduced. Our findings emphasize the role of gene dosage in the tetraploid yeast strains commonly used in commercial ethanol-producing fermentations. Alterations in gene dosage led to increased ethanol production. In combination this research emphasizes the need to identify native Saccharomyces genes whose manipulation, either by deletion or over expression, can increase ethanol yield during fermentation.