Optimizing fermentation: Yeast ethanol tolerance

(1) SABMiller, Loughborough, U.K.

While optimization and consistency of large-scale brewing fermentations from inoculation and dispersal of biomass to product recovery is of critical economic and industrial importance, process innovation requires an effective understanding of the biological constraints and opportunities of the system. Efficient fermentation requires conditions appropriate for ensuring high productivity while maintaining yeast viability and fermentation performance. However, optimal conditions for the former can be sub-optimal for the latter, leading to inconsistent and even “stuck” fermentations. Although it is recognized that yeast is exposed to fluctuations in oxygen concentration, osmotic potential, pH, ethanol concentration, nutrient availability, and temperature, the impact of these stresses on yeast fermentation performance is still not well understood. This paper will focus on the stresses customarily associated with the use of increased gravity from the perspective of osmotic and ethanol tolerance. The paper will demonstrate that previous assumptions concerning the relative impact of certain stresses may not be correct. In particular, we will focus on whether certain stresses could even be beneficial to fermentation.

Katherine Smart completed a B.S. (with honors) degree in biological sciences at Nottingham University in 1987 and was awarded the Rainbow Research Scholarship to complete a Ph.D. degree in brewing yeast and fermentation at Bass Brewers, Burton-on-Trent, England. She then moved to Cambridge University to take up an appointment as a research fellow in the Department of Plant Sciences, where she worked on bioactive surfaces, biofouling, and bacterial contamination of beverages in collaboration with the beverage packaging company Elopak. In 1992, Katherine became a lecturer in microbiology and fermentation at Oxford Brookes University. By 2000, she had been appointed to the Scottish Courage Reader in Brewing Science and became the youngest Fellow of the Institute and Guild of Brewing. In 2005 Katherine moved to the University of Nottingham, where she became the SABMiller Professor in Brewing Science. She was nominated as a Fellow of the Royal Society for the Arts, Manufacturing and Commerce in 2009 and a Fellow of the Society of Biology in 2010. She leads brewing science at the University of Nottingham, which offers a state-of-the-art e-learning M.S. degree in brewing science, and established brewing science research programs in barley genomics, malting, yeast genomics, fermentation, and flavor. She is currently holding some £8 million in research funding for brewing and bioethanol fermentations. Katherine has received several awards for her research, including the Institute of Brewing and Distilling Cambridge Prize (1999), the prestigious Royal Society Industrial Fellowship (2001–2003), an Enterprise Fellowship (2002), and the Save British Science Award at the Houses of Parliament in the UK (2003). Her core research interests are yeast cell biology, fermentation (beer fermentations, bioethanol fermentations), and stress responses in yeast.