Presentation Information
[2Brew-15]Toward General Principles of Alcoholic Fermentation Control in Yeast
○Daisuke Watanabe1 (1. Nara Institute of Science and Technology (Japan))
Keywords:
alcoholic fermentation,sake yeast,Rim15p,lactic acid bacteria,microbial interactions
Alcoholic fermentation is a robust, glycolysis-driven process that enables yeast to gain energy, and its efficiency is not easily reshaped by straightforward manipulation of individual metabolic enzymes. Despite its long history and practical importance, the regulatory logic that tunes fermentation in response to nutritional and ecological contexts remains incompletely understood. Yet fermentation industries have relied on strains empirically selected for high fermentation performance. Our goal is to identify the regulatory principles that govern alcoholic fermentation, and to translate those principles into ways to rationally tune fermentation performance to meet industrial needs.
Using sake yeast as a model genetic resource, we integrated comparative whole-genome analysis with transcriptome profiling during fermentation and identified the stress-responsive protein kinase Rim15p as a key inhibitory regulator of alcoholic fermentation. A loss-of-function allele of RIM15, frequently found in sake yeasts, is associated with elevated fermentation rates. Genetic and physiological analyses indicate that the Rim15p-centered signaling program responds to extracellular nutrient/stress conditions and suppresses glycolytic throughput by diverting carbon away from ethanol production. Specifically, Rim15p promotes carbon flow into UDP-glucose-dependent pathways, increasing the synthesis of the cell-wall 1,3-β-glucan polysaccharide. This glucose-polymer synthesis competes with glycolytic carbon flux, while supporting stress tolerance under harsh fermentation conditions. This regulatory trade-off provides a mechanistic explanation for how sake yeasts achieve high fermentation performance, and it highlights Rim15p-linked signaling as a practical leverage point for controlling alcoholic fermentation in a predictable manner.
Alcoholic fermentation is also shaped by the surrounding biotic community. In a traditional sake starter fermentation (kimoto), we reported that lactic acid bacteria coexisting with yeast remodel the yeast carbon metabolic profile and attenuate alcoholic fermentation. Integrated transcriptome and metabolome analyses further suggest that bacterial cues may trigger metabolic reprogramming via reduced function of the global transcriptional regulatory complex Cyc8p–Tup1p. Most recently, we have also obtained preliminary observations that the plant-derived compound curcumin can enhance alcoholic fermentation, suggesting that chemical signals from coexisting microorganisms and plant materials may modulate yeast activity in fermented-food ecosystems.
Together, our studies define alcoholic fermentation as an integrated systems behavior governed by nutrient signaling and ecological cues that program carbon allocation between ethanol production and stress-adaptive investment. Clarifying these regulatory mechanisms should enable more predictable control of alcoholic fermentation, supporting innovation in fermented foods and beverages.
Using sake yeast as a model genetic resource, we integrated comparative whole-genome analysis with transcriptome profiling during fermentation and identified the stress-responsive protein kinase Rim15p as a key inhibitory regulator of alcoholic fermentation. A loss-of-function allele of RIM15, frequently found in sake yeasts, is associated with elevated fermentation rates. Genetic and physiological analyses indicate that the Rim15p-centered signaling program responds to extracellular nutrient/stress conditions and suppresses glycolytic throughput by diverting carbon away from ethanol production. Specifically, Rim15p promotes carbon flow into UDP-glucose-dependent pathways, increasing the synthesis of the cell-wall 1,3-β-glucan polysaccharide. This glucose-polymer synthesis competes with glycolytic carbon flux, while supporting stress tolerance under harsh fermentation conditions. This regulatory trade-off provides a mechanistic explanation for how sake yeasts achieve high fermentation performance, and it highlights Rim15p-linked signaling as a practical leverage point for controlling alcoholic fermentation in a predictable manner.
Alcoholic fermentation is also shaped by the surrounding biotic community. In a traditional sake starter fermentation (kimoto), we reported that lactic acid bacteria coexisting with yeast remodel the yeast carbon metabolic profile and attenuate alcoholic fermentation. Integrated transcriptome and metabolome analyses further suggest that bacterial cues may trigger metabolic reprogramming via reduced function of the global transcriptional regulatory complex Cyc8p–Tup1p. Most recently, we have also obtained preliminary observations that the plant-derived compound curcumin can enhance alcoholic fermentation, suggesting that chemical signals from coexisting microorganisms and plant materials may modulate yeast activity in fermented-food ecosystems.
Together, our studies define alcoholic fermentation as an integrated systems behavior governed by nutrient signaling and ecological cues that program carbon allocation between ethanol production and stress-adaptive investment. Clarifying these regulatory mechanisms should enable more predictable control of alcoholic fermentation, supporting innovation in fermented foods and beverages.
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