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Highlights • WGH supplementation improved the tolerance to osmotic and ethanol stress in yeast. • WGH supplementation improved ethanol production of yeast under VHG fermentation. • WGH addition caused the decrease in ROS and the increase in membrane integrity. • WGH addition increased the levels of intracellular glycerol and trehalose in yeast. • 40% ethanol fraction from WGH showed the best bioactivity for yeast cells. Abstract Wheat gluten hydrolysates (WGH) and their fractions (0%, 20% and 40% ethanol fractions) obtained on XAD-16 were used to examine their effects on multiple stress tolerance and ethanol fermentation performances of yeast during very high-gravity (VHG) fermentation. Results showed that WGH and their fractions supplementations increased significantly osmotic/ethanol stress tolerance, growth and vitality of yeast cells. Supplementation with 40% ethanol fraction resulted in 46.54% and 35.01% of increase in cell membrane integrity, and 42.59% and 21.79% of reduction in intracellular ROS level under osmotic and ethanol stress conditions, respectively. Moreover, WGH and their fractions supplementations also increased physiological activity and ethanol yield of yeast cells under VHG fermentation, and 40% ethanol fraction supplementation caused the maximum biomass and ethanol production during VHG fermentation. These results suggested that WGH supplementation was an efficient and convenient method for improvement of yeast cells with enhanced multiple stress tolerance and ethanol fermentation performances. [ABSTRACT FROM AUTHOR]

Highlights • Wheat gluten hydrolysates (WGH) and soy protein hydrolysates (SPH) were prepared. • WGH and SPH exhibited significant yeast growth and fermentation promoting activity. • The bioactivity was not linear with the degree of hydrolysis and addition amount. • Bioactivity of hydrolysates was related to the molecular structure characteristics. • Glu, Leu, Lys and Arg in hydrolysates were responsible for their bioactivity. Abstract Wheat gluten hydrolysates (WGH) and soy protein hydrolysates (SPH) were used to examine their effects on the growth and fermentation performance of yeast during high-gravity fermentation. Results showed that both the kind and the addition amount of hydrolysates had significant impacts on the biomass, viability, fermentability and ethanol yield of yeast cells. Worts supplemented with WGH and SPH (with the hydrolysis time of 24 h and 12 h, and the addition amount of 1.0% and 0.1%, respectively) increased 5.5% and 12.6% of net cell growth, 0.3% and 1.1% of fermentability, and 19.3% (v/v) and 23.7% (v/v) of ethanol yields, respectively. All these results indicated that both hydrolysates were effective and preferential nitrogen sources for yeast growth and fermentation. The moderate molecular weight distribution, the complexity of nitrogen source and the higher hydrophilic and basic amino acids contents in hydrolysates might be responsible for their specific bioactivity. [ABSTRACT FROM AUTHOR]