Efficient fermentation of very high-gravity worts by brewer's yeast with wheat gluten hydrolysates and their ultrafiltration fractions supplementations.

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]