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Abstract Very high-gravity (VHG) worts (24 °P) supplemented with wheat gluten hydrolysates (WGH) and their ultrafiltration fractions (Mw > 1 kDa and <1 kDa fractions) were used to evaluate their effects on physiological activity and ethanol fermentation of brewer's yeast. The results demonstrated that WGH and their ultrafiltration fractions supplementations could obviously improve the biomass and viability of yeast, and further enhance the sugar utilization and ethanol production under VHG fermentation. Supplementation with Mw < 1 kDa fraction exhibited the maximum biomass (6.90 g/L dry cell), sugar utilization (79.79%) and ethanol concentration (11.88%, v/v) during VHG fermentation. Meanwhile, the addition of Mw < 1 kDa fraction significantly decreased the plasma membrane permeability and intracellular reactive oxygen species (ROS) accumulation, and increased the mitochondrial membrane potential in cells during VHG fermentation. Moreover, Mw < 1 kDa fraction supplementation caused the highest accumulations of intracellular trehalose and glycerol, which were 12.10% and 31.22% higher than the control, respectively. These results illustrated that WGH (especially Mw < 1 kDa fraction) addition was an economic and efficient method to improve physiological activity and ethanol fermentation of brewer's yeast in VHG worts. Highlights • WGH and their ultrafiltration fractions were obtained as nitrogen sources of yeast. • WGH supplementation changed nitrogen metabolism of yeast during VHG fermentation. • Biomass and ethanol production were increased by WGH addition under VHG condition. • Physiological activity of yeast was improved by WGH addition under VHG condition. • Trehalose and glycerol in yeast accumulated by WGH addition under VHG condition. [ABSTRACT FROM AUTHOR]

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]

Wheat gluten hydrolysates (WGH) were used to examine their adsorption–desorption kinetics and thermodynamics characteristics on six macroporous resins, and their effects on the stress tolerance in brewer’s yeast. Results showed that the pseudo second-order kinetics, Langmuir and Freundlich model could illuminate the adsorption mechanism, and the adsorption process was physical, spontaneous and exothermic. The 40% ethanol fraction separated by XAD-16 resin improved significantly the ethanol tolerance and the viability of brewer’s yeast, while the 0% ethanol fraction separated by XAD-16 resin increased obviously the osmotic stress tolerance and the viability of brewer’s yeast. Results from scanning electron microscopy showed that both these WGH fractions could increase budding rate and maintain normal morphology of yeast cells under various environmental stress. Thus, WGH separated by macroporous resin could be used in high gravity brewing to enhance the ethanol and osmotic stress tolerance in brewer’s yeast. [ABSTRACT FROM AUTHOR]

Summary: Wheat gluten hydrolysates (WGH) were fractionated through ultrafiltration membrane with molecular weight (Mw) cut‐off of 3 kDa and ethanol precipitation, respectively. WGH and their fractions were used to examine their effects on the growth and fermentation performances of brewer's yeast under high gravity fermentation. Results showed that WGH and their fractions exhibited significant differences in biomass accumulation, viability, ethanol yield, free amino nitrogen and sugar consumptions under high gravity fermentation. Compared to WGH, the fractions with Mw < 3 kDa and the supernatant of WGH treated with ethanol precipitation showed better fermentation performance for brewer's yeast. The relatively lower molecular weight and the higher levels of Leu, Lys, His and Arg in these two fractions might be responsible for their bioactivity for brewer's yeast. Thus, both ultrafiltration and ethanol precipitation could be used as efficient methods for enriching peptides with significant growth‐ and fermentation‐promoting activity for brewer's yeast under high gravity fermentation. [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]