• Korean Journal of Food Science and Technology
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• v.49 no.2
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• pp.168-172
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• 2017

In this study, the fermentative characteristics of rye sourdough fermented with Omija extract were investigated. The pH and total titratable acidity, numbers of yeast and lactic acid bacteria, and expansion rate were measured. While the pH of Omija rye sourdough decreased from 5.60 to 3.86, the total titratable acidity significantly increased from 2.39 to 8.50 with fermentation time (p<0.05). The numbers of yeast and lactic acid bacteria significantly increased for 18 h of fermentation period (p<0.05). The expansion rate of Omija rye sourdough showed a maximum of 183%, more than 47% more than the highest value of rye sourdough (129%). These results suggest that the application of Omija extract for making sourdough could be a good way to decrease the sanitary risk especially for early stage of sourdough fermentation. In addition, Omija rye sourdough could contribute to improvement of baking quality such as volume increase and flavor improvement of rye bread.

• Korean journal of food and cookery science
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• v.15 no.1
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• pp.73-80
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• 1999

This study was carried out to investigate the effects of enzyme treatments on the functional properties of soy protein isolate (SPI) and to examine the quality attributes of soy yogurt prepared by different enzyme treatments, sweeteners and starter cultures. Enzyme treatment increased the solubility and emulsifying capacity of soy proteins, but decreased the emulsifying stability; the enzymatic activity of ${\alpha}$-chymotrypsin was higher than that of trypsin. Enzyme treatments decreased the pH of soy yogurts prepared by both culture methods, the culture of L. bulgaricus and S. thermophilus and the culture of L. bulgaricus and K. fragilis, but increased the titratable acidity, total numbers of lactic acid bacteria and yeast. Trypsin was more effective than ${\alpha}$-chymotrypsin in decreasing pH and increasing titratable acidity and total numbers of lactic acid bacteria and yeast. Fructose decreased the pH of soy yogurts more than sucrose in the culture of L. bulgaricus and S. thermophilus, and vice versa in the culture of L. bulgaricus and K. fragilis. Fructooligosaccharides were more effective in the culture of L. bulgaricus and K. fragilis than in the culture of L. bulgaricus and S. thermophilus in increasing the titratable acidity, total count of lactic acid bacteria and yeast. In sensory evaluation, soy yogurts containing trypsin treated SPI, fructose and fructooligosaccharides (75%:25%) were more acceptable than those containing untreated or trypsin treated SPI and fructose. This was because of more smooth and less sour, in which the values of pH, titratable acidity, microbial growth, and viscosity were in the range of commercial yogurts. Soy yogurts fermented by L. bulgaricus and K. fragilis showed more smooth mouthfeel than those fermented by L. bulgaricus and S. thermophilus.

• Journal of Microbiology and Biotechnology
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• v.26 no.11
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• pp.1891-1907
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• 2016

Yeasts that are present in marine environments have evolved to survive hostile environments that are characterized by high exogenous salt content, high concentrations of inhibitory compounds, and low soluble carbon and nitrogen levels. Therefore, yeasts isolated from marine environments could have interesting characteristics for industrial applications. However, the application of marine yeast in research or industry is currently very limited owing to the lack of a suitable isolation method. Current methods for isolation suffer from fungal interference and/or low number of yeast isolates. In this paper, an efficient and non-laborious isolation method has been developed and successfully isolated large numbers of yeasts without bacterial or fungal growth. The new method includes a three-cycle enrichment step followed by an isolation step and a confirmation step. Using this method, 116 marine yeast strains were isolated from 14 marine samples collected in the UK, Egypt, and the USA. These strains were further evaluated for the utilization of fermentable sugars (glucose, xylose, mannitol, and galactose) using a phenotypic microarray assay. Seventeen strains with higher sugar utilization capacity than the reference terrestrial yeast Saccharomyces cerevisiae NCYC 2592 were selected for identification by sequencing of the ITS and D1/D2 domains. These strains belonged to six species: S. cerevisiae, Candida tropicalis, Candida viswanathii, Wickerhamomyces anomalus, Candida glabrata, and Pichia kudriavzevii. The ability of these strains for improved sugar utilization using seawater-based media was confirmed and, therefore, they could potentially be utilized in fermentations using marine biomass in seawater media, particularly for the production of bioethanol and other biochemical products.

• Korean Journal of Food Science and Technology
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• v.30 no.5
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• pp.1134-1139
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• 1998

Quality changes of filter-sterilized Yakju were examined by filtration of Yakju through membranes followed by storing at $25^{\circ}C$ for 50 days. To evaluate quality changes of filter-sterilized Yakju, pH, titratable acidity, turbidity, and viable cell numbers of total bacteria, lactic acid bacteria, and yeast were measured. Titratable acidity, turbidity and viable cell numbers of non-sterilized Yakju increased, but pH profile decreased during the storage. In filter-sterilized Yakju, titratable acidity and turbidity did not change, while viable cells of total bacteria, lactic acid bacteria, and yeast were not detected during the storage. Addition of chitosan at the concentration of 0.1% (w/v) decreased the viable cell numbers significantly showing similar pH and titratable acidity profiles with non-sterilized Yakju.

• Food Science and Biotechnology
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• v.15 no.2
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• pp.298-302
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• 2006

Kochujang was fermented using hot red pepper, meju prepared with soybean and rice, and malt-digested syrup. To reduce salt content, mustard powder (1.2%, w/w) was added to Korean traditional kochujang with 4-10% salt, and microbial characteristics, enzyme activities, and gas formation in kochujang were evaluated during fermentation for 120 days at $25^{\circ}C$. Yeast numbers of all treatments maintained 2.43-2.86 log CFU/g up to 60 days fermentation, indicating salt concentration had no effect on yeast count. Activities of ${\alpha}$- and ${\beta}$-amylases, and neutral and acidic proteases of kochujang added with mustard powder were slightly higher than those of control group. Total accumulative volume of gas produced during fermentation of kochujang without mustard powder (control group) was 5,892 mL/pack, but decreased to 34-99 mL/pack in low-salted kochujang (4 and 6% salt) added with mustard powder. Major gas produced was carbon dioxide (79-80%) with oxygen content less than 1.25%(v/v). Results indicate salt concentration of kochujang could be lowered up to 6-8% by addition of mustard powder without gas formation and quality alteration during distribution.

• Archives of Pharmacal Research
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• v.16 no.3
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• pp.231-236
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• 1993

Gly-224 residue of yeast alcohol dehydrogenase was mutated by site-directed mufagenesis to isoleucine, which is the corresponding amino acid residue of horse liver alcohol dehydrogenase. The mutated gene on M13 vector was subcloned in YEp13 and used to transform Saccharomyces cerevisiae 302-21 #2 strain, and the expressed protein was purified. The tumover numbers of mutant enzyme for ethanol and acetaldehyde were decreased copared to wild-type enzyme. The results of product inhibition studies indicated that the reaction mechanism was changed to Iso Theorell-Chance from Ordered Bi Bi. We supposed that Gly-224 was related to the enzyme reaction mechanism.

• Korean Journal of Poultry Science
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• v.34 no.2
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• pp.137-141
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• 2007

This experiment was conducted to investigate the effects of dietary yeast (Saccharomyces exguus) supplementation on growth performance, cecal microflora and fecal ammonia gas in broiler chicks. A total of two hundred seventy, 1-d-old male broiler chicks (Ross strain) were randomly allotted to nine pens (replicates), 30 birds per pen. There were three dietary treatments with three replicates. The treatments were control (virginiamycin 0.05%+salinomycin 0.03%), Saccharomyces exguus 0.5 and 1.0%. Total body weight gain were significantly higher in Saccharomyces exguus1 1.0% treatment than the control (P<0.05). Although not significant, the yeast supplementation tended to improve the feed conversion ratio. No significant differences were observed on the numbers of cecal E. coli, Salmonella and Lactobacillus in yeast treatments compared to those of control. The production of fecal ammonia gas was significantly lower in yeast treatments than the control (P<0.05). The concentrations of fecal short chain fatty acids and volatile organic compounds were not different among the groups. These results suggest the possibility that yeast (Saccharomyces exguus) could be used as the alternative of antibiotic growth promoters by improving the performance of broiler chicks. In addition, dietary yeast could improve the environment of broiler houses by reducing fecal ammonia production.

• Korean Journal of Food Science and Technology
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• v.42 no.3
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• pp.281-286
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• 2010

The objective of this study was to analyze the microbial populations in the raw ingredients of kimchi and their changes during an automated commercial manufacturing process. High population numbers of total aerobic bacteria, lactic acid bacteria, Leuconostoc sp., and yeast were detected in garlic, ginger, red pepper powder and this result revealed that these ingredients were the major source of microbials in kimchi. Additionally, during the salting process of Chinese cabbage, rapid microbial growth was observed and the consecutive washing process was determined to be ineffective, lowering the microbial count by only one log reduction. Yeast was also detected in various ingredients. These results strongly suggest that, in order to lower the microbial population numbers in kimchi, the side-ingredients and salting process should be subjected to the appropriate sanitization or sterilization processes at the HACCP level. Beside, treatment of salted Chinese cabbage with sodium hypochlorite solutions after the salting step is recommended. To inhibit yeast growth, appropriate chemical treatment and approval of additive uses to control microbials should be considered. These experimental results and suggestions will be used to improve the kimchi manufacturing process in factories.

• Microbiology and Biotechnology Letters
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• v.21 no.3
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• pp.214-220
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• 1993

The mating type a of yeast, Saccharomyces cerevisiae mutant with hmla2-102 and sir3-8ts was changed to type alpha by changing the growth temperature from 25C to 35C. A temperature-sensitive expression vector system was constructed using mating factor alpha1 (Mfalpha1) gene encoding alpha factor which is expressed in the type alpha cells. Vectors with different copy numbers were constructed by joining the promoter and pre or prepro-secretion single sequence of Mfalpha1 to promoterless PHO5' gene as a reporter gene.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.5
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• pp.466-469
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• 2006

The bed stability of Streamline DEAE (p = 1.2 g/mL) in a 20mm (i.d.) glass expanded bed contactor, and its performance on the recovery of glucose 6-phosphate dehydrogenase (G6PDH) from unclarified yeast homogenate were investigated. A residence time distribution study showed that a stable expanded bed was achieved. The theoretical plate and Bodenstein numbers determined were 25 and 53, respectively. A recovery yield of 87% and purification factor of 4.1 were achieved in the operation using 5% (w/v) biomass concentration feedstock. The performance of the anion exchange EBAC was still considerable good at a biomass concentration as high as 15% (w/v).