O-18. Serial repitching: Does yeast generation number matter?

Presenter: Katherine Smart, University of Nottingham, Loughborough, U.K..

Serial repitching is a common practice in brewing. Great care is taken to ensure that a yeast crop is recovered and stored effectively before reuse in subsequent fermentations, with the expectation that performance will be consistent irrespective of the number of fermentations a crop has completed (generation number). Early generation yeast tends to be slow to perform, while later generation yeast tends to exhibit genetic changes, poor viability, and inconsistent flocculation and flavor profiles. Efficient fermentation requires conditions appropriate for ensuring high productivity, while maintaining yeast viability, genetic stability, and fermentation performance. However, optimal conditions for the former can be sub-optimal for the latter. This paper will focus on the stresses customarily associated with fermentation, providing insight into the reasons why yeast generation is important. This 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. (honors) degree in biological sciences at Nottingham University in 1987 and was awarded the Rainbow Research Scholarship to complete a Ph.D. in brewing yeast and fermentation at Bass Brewers, Burton-on-Trent. 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 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 has established brewing science research programs in barley genomics, malting, yeast genomics, fermentation, and flavor. She currently holds 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 United Kingdom (2003). Her core research interests are yeast cell biology, fermentation (beer fermentations, bioethanol fermentations), and stress responses in yeast.

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