Search

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]

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]

By sampling the wort from different stages of mashing and boiling, part of the sample was used for the acquisition of three spectra (NIR, Raman and UV–Vis) and the other part for chemical analysis. The results of chemical analysis and spectra were combined using chemometrics, and three models of PLS((Partial Least Squares), LS-SVM(Least Squares Support Vector Machines), and NN(Neural Networks) were developed to quantify reducing sugar, free amino nitrogen, and total phenols contents in wort. The aim of the study is to investigate the best spectra and models for the quantitative analysis of key wort components during mashing and boiling of Qingke malt, so as to achieve real-time monitoring of the Qingke beer brewing process. [Display omitted] • Qingke malt has the potential to become a raw material for beer brewing. • Quantitative models were developed using three spectra in combination with chemometrics. • The study focuses on the brewing process of beer to make it clearer and more controllable. In order to monitor the Qingke beer brewing process in real time, this paper presents an analytical method for predicting the content of key components in the wort during the mashing and boiling stages using multi-spectroscopy combined with chemometrics. The results showed that the Neural Networks (NN) model based on Raman spectroscopy (RPD = 3.9727) and the NN model based on NIR spectroscopy (RPD = 5.1952) had the best prediction performance for the reducing sugar content in the mashing and boiling stages; The partial least Squares (PLS) model based on Raman spectroscopy (RPD = 2.7301) and the NN model based on Raman spectroscopy (RPD = 4.3892) predicted the content of free amino nitrogen best; The PLS model based on UV–Vis spectroscopy (RPD = 4.0412) and the NN model based on Raman spectroscopy (RPD = 4.0540) are most suitable for the quantitative analysis of total phenols. The results can be used as a guide for real-time control of wort quality in industrial production. [ABSTRACT FROM AUTHOR]