Truncation of CYR1 promoter in industrial ethanol yeasts for improved ethanol yield in high temperature condition

Abstract

Abstract As the initiation of fermentation using the yeast Saccharomyces cerevisiae is always associated with a rapid drop in stress resistance, it is critical to develop yeast cells with elevated stress tolerances as well as normal growth and metabolite rates. In our study, the CYR1 promoter was serially truncated from the 3′end by 30 bp steps to finely modulating the activity of Adenylate cyclase, encoded by CYR1 and synthesizing cAMP from ATP. The constructed mutants AY15a-90 and AY15a-120, whose promoters carry 90- and 120-bp truncations, showed a 2- and 3-fold drop in adenylate cyclase activity, and improved heat and ethanol tolerances than AY15a. Interestingly, AY15a-90 and AY15a-120 also exhibited the same growth and fermentation rate as the strain AY15a. In very high gravity (VHG) fermentation at 40 °C, the yield of ethanol for AY15a-90 and AY15a-120 were 14% and 15% higher than that of AY15a, respectively. These results showed high stress tolerance and high fermentation activity could be compatible by finely modulating the expression of CYR1.