Abstract
The effects of wheat gluten hydrolysates (WGH) and their ethanol elution fractions obtained on XAD-16 resin on physiological activity and fermentation performance of brewer’s yeast during very-high-gravity (VHG) worts fermentation were investigated. The results showed that the addition of WGH and their elution fractions in VHG worts significantly enhanced yeast biomass and viability, and further increased the fermentability, ethanol yield and productivity of yeast. Supplementation with 40% ethanol fraction exhibited the highest biomass (6.9 g/L dry cell), cell viability, fermentability (82.05%), ethanol titer (12.19%, v/v) and ethanol productivity during VHG worts fermentation. In addition, 40% ethanol fraction supplementation also caused the most consumption of amino acid and the highest accumulation of intracellular glycerol and trehalose, 15.39% of increase in cell-membrane integrity, 39.61% of enhancement in mitochondrial membrane potential (MMP), and 18.94% of reduction in intracellular reactive oxygen species (ROS) level in yeast under VHG conditions. Therefore, WGH supplementation was an efficient method to improve fermentation performance of brewer’s yeast during VHG worts.
Highlights
With the development of beer brewing industry, cost and energy savings become especially important to modern brewery
Amino acid compositions of wheat gluten hydrolysates (WGH) and their ethanol fractions Physiological and fermentation properties of yeast cells were affected by the composition of nitrogen source during fermentation process (Zhou et al 2018; Xu et al 2019)
WGH-A 40% ethanol fraction (WGH-D) contained the highest levels of peptides, followed by WGH-A 20% ethanol fraction (WGH-C) (91.68%), Wheat gluten hydrolysates supernatant (WGH-A) (86.42%) and WGH-A water-washed fraction (WGH-B) (66.42%). These results further suggested that XAD-16 resin could be used for peptide enrichment from WGH
Summary
With the development of beer brewing industry, cost and energy savings become especially important to modern brewery. Pitching yeast cells would encounter hyperosmolarity and high ethanol concentration during VHG worts fermentation (Burphan et al 2018; Yang et al 2019a). All of these stresses affect physiological activity of yeast, and ethanol production, which would result to a slow or stuck fermentation (Auesukaree 2017; Zhang et al 2017; Burphan et al 2018). Wheat gluten hydrolysates (WGH) have been proved to have various bioactivity, such as antioxidant activity, opioid-like activity, immunological activity, and enhanced stress tolerance in yeast (Huebner et al 1984; Horiguchi et al 2005; Koo et al 2014; Yang et al 2019a). The possible mechanisms of improved physiological activity and fermentation performance of yeast cells associated with WGH addition were revealed
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