Preventing sluggish or stuck fermentations which may be caused by sugar uptake deficiency in saccharomyces cerevisiae wine yeast strains by using glucose isomerase

Ünal, Nahide Seray
The objective of this study was to prevent stuck fermentation, which may be caused by sugar uptake deficiency in yeast by using glucose isomerase, whose activity was tested in different media. The unfermented grape juice contains almost equal amounts of glucose and fructose. After fermentation, amount of residual fructose is higher than that of glucose and the glucose/fructose discrepancy (GFD) occurs. One of the main reasons of GFD is that affinity of hexose transporters of yeast towards fructose decreases as the accumulation of ethanol increases. Due to formation of ethanol, fermentation slows or stops even if there is residual sugar in wine medium. This is called stuck fermentation. This is an undesirable situation since residual sugar causes unwanted sweetness and increases the risk of microbial spoilage. To prevent GFD, using glucose isomerase during or after wine fermentation may be a solution. The activity of this enzyme was tested in synthetic and original wine media to find out whether it can be a solution for stuck fermentation or not. Glucose formation, 0.5% w/v, from 1% w/v fructose occurred in synthetic medium containing 13% v/v ethanol and 1% v/v glycerol at pH 3.3 and at temperatures of 60ºC or 30ºC in approximately 48 hours. However, the glucose formation did not occur in synthetic medium if there was 0.3% w/v tartaric acid at pH 3.55 whereas glucose was formed at pH 6.33. In original wine medium, the glucose formation did not occur except that wine media with dilution factor of 20% v/v, 10% v/v and 5% v/v and at pH values equal or higher than 6 whether there was tartaric acid or not. Since dilution and increasing the pH of wine cannot be applicable, other ways to employ this enzyme should be tried.


Recovery of acids from anaerobic acidification broth by liquid-liquid extraction
Alkaya, Emrah; Kaptan, Serkan; Ozkan, Leyla; Uludag-Demirer, Sibel; Demirer, Göksel Niyazi (2009-11-01)
In this study, anaerobic acidification of sugar beet processing wastes and subsequent liquid-liquid extraction of produced fermentation metabolites were investigated. The aim of extraction experiments was to asses the influence of pH and extractant (trioctylphosphine oxide (TOPO) in kerosene) concentrations on the recovery of volatile fatty acids (VFAs) from fermentation broth. The effect of TOPO in kerosene concentration was as crucial as the effect of pH on the recovery of VFAs via extraction. Consequentl...
Photofermentative hydrogen production from volatile fatty acids present in dark fermentation effluents
Uyar, Basar; Eroglu, Inci; Yucel, Meral; Gündüz, Ufuk (2009-05-01)
In the present study, the growth and hydrogen production of Rhodobacter sphaeroides O.U. 001, was investigated in media containing five different volatile fatty acids (VIA) individually (malate, acetate, propionate, butyrate and lactate) and in media containing mixtures of these acids that reflect the composition of dark fermentation effluents. The highest hydrogen production rate was obtained in malate (24 ml(hydrogen)/I(reactor)h) and the highest biomass concentration was obtained in acetate containing me...
Use of pulsed-high hydrostatic pressure treatment to decrease patulin in apple juice
Avsaroglu, M. D.; Bozoglu, F.; Alpas, Hami; LARGETEAU, ALAIN; Demazeau, G. (Informa UK Limited, 2015-04-03)
This study was aimed at reducing patulin content of apple juice using a non-thermal method, namely pulsed-high hydrostatic pressure (p-HHP). Commercially available clear apple juice was contaminated artificially with different concentrations of patulin (5, 50 and 100 ppb). Then, the samples were processed 5 min at different pressure treatments (300-500 MPa) in combination with different temperatures (30-50 degrees C) and pulses (6 pulses x 50 s and 2 pulses x 150 s). To compare the impact of pulses, single ...
High hydrostatic pressure-assisted extraction of lipids from Lipomyces starkeyi biomass
Tuhanioglu, Arda; Alpas, Hami; Çekmecelioğlu, Deniz (2022-10-01)
The purpose of this study is to evaluate the effect of high hydrostatic pressure (HHP) as a novel approach for yeast cell disruption and lipid extraction from Lipomyces starkeyi DSM 70295 grown in glucose medium (40 g/L and C/N:55/1) at initial pH of 5.0, 25 degrees C, and 130 rpm for 8 days. HHP extraction conditions including pressure, time, and temperature were optimized by response surface methodology. The high speed homogenizer-assisted extraction (HSH) was also used for comparison. The biomass subject...
Separation of the protease enzymes of Bacillus licheniformis from the fermentation medium by crossflow ultrafiltration
Takac, S; Elmas, S; Çalık, Pınar; Ozdamar, TH (2000-06-01)
The separation from fermentation medium of extracellular serine alkaline protease (SAP) enzyme produced by Bacillus licheniformis was investigated using a crossflow ultrafiltration system. SAP was separated from the high molecular weight neutral protease (NP) and amylase (AMY) enzymes and from the low molecular weight organic acids and amino acids in a crossflow ultrafiltration system with 30000 Da and 10000 Da MWCO polysulfone membranes, respectively. The effects of transmembrane pressure (TMP), recirculat...
Citation Formats
N. S. Ünal, “Preventing sluggish or stuck fermentations which may be caused by sugar uptake deficiency in saccharomyces cerevisiae wine yeast strains by using glucose isomerase,” Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Food Engineering., Middle East Technical University, 2019.