• Journal of Microbiology
• /
• v.33 no.4
• /
• pp.322-327
• /
• 1995

Tolerance of Mycobacterium sp. against organic solvents has been induced for the cholesterol side chain degradation by adding chemicals associated with synthesis of fatty acids or alcohols. Biotin of 300 .mu.g/1 and 0.5% aqueous ethanol solution were optima for the enhancement of ethanol tolerance of the microorganism. The induction of ethanol tolerance by biotin was found to be due to increase of degree of unsaturation of the fatty acids in membranous phospholipid of the cell, especially due to increase of oleic acid content. However when 0.5% of ethanol was added for the ethanol tolerance induction, there was an ambiguous correlation between ethanol tolerance and degree of unsaturation of the fatty acids, in spite of the fact that the induction increased the content of unsaturated fatty acids. Addition of 0.5% of ethanol induced several ethanol shock proteins having molecular weight similar to that of heat shock proteins.

• Journal of Microbiology and Biotechnology
• /
• v.1 no.3
• /
• pp.151-156
• /
• 1991

In order to construct a yeast strain having high ethanol tolerance together with good lactose fermentation ability, the protoplast fusion using Saccharomyces cerevisiae STV 89 and Kluyveromyces fragilis CBS 397 was carried out. Auxotrophic mutants of K. fragilis were obtained as a selection marker by treatment of ethylmethane sulfonate. The best mutant for protoplast fusion was selected based on the capabilities of ${\beta}-galactosidase$ production and lactose fermentation. The protoplast fusion using polyethylene glycol and calcium chloride solution led to the fusion frequence of $3{\times}10^{-6}$ and a number of fusants were obtained. Among these fusants, a fusant F-3-19 showed the best results in terms of ethanol tolerance, ${\beta}-galactosidase$ activity and lactose fermentation. The performance of lactose fermentation and ethanol tolerance by this fusant were better than those of K. fragilis. Study on the ethanol tolerance having relation to fatty acid composition and intracellular ethanol concentration revealed that the fusant F-3-19 had a higher unsaturated fatty acids content and accumulated less amount of intracellular ethanol compared with a parent of K. fragilis.

• Journal of Microbiology and Biotechnology
• /
• v.1 no.1
• /
• pp.6-11
• /
• 1991

This study deals with investigation of the ethanol tolerance of yeast strains with respect to fatty acid composition and intracelluar ethanol concentration during alcohol fermentation. The cell viabilities and fermentation abilities of Saccharomyces cerevisiae and Kluyveromyces fragilis were improved by aeration and addition of unsaturated fatty acids into growth medium. Aeration decreases the accumulation of ethanol, while increases unsaturated fatty acid contents inside yeast cells. Thus it was found that oxygen and unsaturated fatty acids play decisive roles in the increase of ethanol tolerance of yeasts.

• Microbiology and Biotechnology Letters
• /
• v.22 no.6
• /
• pp.584-592
• /
• 1994

Several mutation procedures have been compared to obtain an ethanol-tolerant Saccha- romyces diastaticus strain secreting glucoamylase. These procedures include spontaneous mutation, EMS treatment, UV irradiation, and combination of EMS treatment and UV irradiation. All these methods were followed by adaptation of the yeast cells to gradually higher ethanol concentration. Among these procedures, the combined method of EMS treatment and UV irradiation gave the promising result, i.e. the ethanol tolerance of the yeast increased from 11.5%(v/v) to 14.0%(v/v). Respiratory deficient petite mutants of industrial and ethanol-tolerant yeast strains have been isola- ted and hybridized with haploid S. diastaticus strains. The resulting hybrids showed increased ethanol tolerance and starch-fermentability.

• Microbiology and Biotechnology Letters
• /
• v.24 no.6
• /
• pp.726-732
• /
• 1996

To improve the fermentation characteristics(such as starch-degradability, ethanol tolerance, sugar and high-temperature tolerance) of recombinant haploid yeast Saccharomyces diastaticus K114, hybridization technique was used. The hybridization partner was S. diastaticus 1177 which had good glucoamylase activity and fermentabi- lity. The best hybrid HH64 showed improved ethanol tolerance, sugar and high-temperature tolerance. Especia- lly, the starch-fermentability was significantly improved, since the hybrid produced 1.60% (w/v) ethanol from 4% (w/v) starch, while the recombinant haploid K114 produced 1.30% (w/v) ethanol. The optimum temperature and pH for the starch-fermentation by the hybrid HH64 was 30$\circ$C and 5, respectively. The hybrid yeast HH64 produced 7.5% (w/v) ethanol directly from 20% (w/v) starch.

• KSBB Journal
• /
• v.4 no.2
• /
• pp.167-171
• /
• 1989

The alcohol fermentation using glucose and lactose was carried out to study the effect of fermentation temperature on the ethanol tolerance of Saccharomyces cerevisiae STV89 and Kluyveromyces fragilis CBS397. The maximum specific growth rate and ethanol production rate were increased up to 35$^{\circ}C$ with the fermentation temperature, although maximum ethanol and cell concentration were decreased by increasing the fermentation temperature. The cell viability was also improved by lowering the fermentation temperature. Under the experimental conditions, the best ethanol tolerance of yeast strains was obtain at $25^{\circ}C$. The ethanol tolerance of S. cerevisiae is better than that of K. fragilis at the same fermentation condition. With respect to the carbon source, glucose is found to be more favorable for ethanol tolerance of K. fragilis than lactos.

• Korean Journal of Microbiology
• /
• v.30 no.5
• /
• pp.377-382
• /
• 1992

The responses of C. jejuni to ethanol shock were studied for their survival. synthesis of ethanol shock proteins, and increased survival at higher concentration of ethanol upon prior treatments of ethanol. When C. jejuni were shocked with ethanol at 1. 3. and 5% for 60. 30 and 10 minutes, respectively. those cells synthesized the ethanol shock proteins of 90, 66, 60, 45, and 24 kd in molecular weight. When the C. ,jejuni shocked with 1 and 3% ethanol were exposed to 3 and 5% ethanol for 30 minutes. their survival rates were increased by $10^1$~$10^2$ as compared with those of the cells without ethanol-shock. In the same way. C. ,jejuni shocked with 5% ethanol for 10 minutes :.bowed about 102 times higher survival rates than the cells without ethanol-shock. This result suggests that C jejuni shocked with I-5% ethanol for 10-30 minutes synthesized five kinds of ethanol shock proteins. and that the shock proteins contributed to increase ethanol tolerance for their survival at the higher concentrations of ethanol.

• Journal of Microbiology and Biotechnology
• /
• v.20 no.7
• /
• pp.1156-1162
• /
• 2010

During ethanol fermentation, bacterial strains may encounter various stresses, such as ethanol and acid shock, which adversely affect cell viability and the production of ethanol. Therefore, ethanologenic strains that tolerate abiotic stresses are highly desirable. Bacteria of the genus Deinococcus are extremely resistant to ionizing radiation, ultraviolet light, and desiccation, and therefore constitute an important pool of extreme resistance genes. The irrE gene encodes a general switch responsible for the extreme radioresistance of D. radiodurans. Here, we present evidence that IrrE, acting as a global regulator, confers high stress tolerance to a Zymomonas mobilis strain. Expression of the gene protected Z. mobilis cells against ethanol, acid, osmotic, and thermal shocks. It also markedly improved cell viability, the expression levels and enzyme activities of pyruvate decarboxylase and alcohol dehydrogenase, and the production of ethanol under both ethanol and acid stresses. These data suggest that irrE is a potentially promising gene for improving the abiotic stress tolerance of ethanologenic bacterial strains.

• Journal of Life Science
• /
• v.29 no.8
• /
• pp.916-921
• /
• 2019

In this study, we constructed a biological system that exhibited thermotolerance, ethanol tolerance, and increased ethanol productivity using a random mutagenesis method. We attempted to isolate a thermotolerant mutant using proofreading-deficient DNA polymerase ${\delta}$ and ${\varepsilon}$ encoded by the pol3 and pol2 genes, respectively, in Saccharomyces cerevisiae. To obtain mutants that could grow at high temperatures ($38^{\circ}C$ and $40^{\circ}C$), random mutagenesis of AMY410 (pol2-4) and AMY126 (pol3-01) strains was induced. The parental strains (AMY410 and AMY126) grew poorly at temperatures higher than $38^{\circ}C$. By stepwise elevation of the incubation temperature, AMY410-Ht (heat tolerance) and AMY126-Ht strains that proliferated at $40^{\circ}C$ were obtained. These strains were further incubated in medium containing 6% and 8% ethanol and then AMY410-HEt (heat and ethanol tolerance) and AMY126-HEt strain with ethanol tolerance at an 8% ethanol concentration was obtained. The AMY126-HEt strain grew even at an ethanol concentration of 10%. Furthermore, following the addition of high concentrations of glucose (5% and 10%), an AMY126-HEt3 strain with increased ethanol productivity was isolated. This strain produced 24.7 g/l of ethanol (95% theoretical conversion yield) from 50 g/l of glucose. The findings demonstrate that a new biological system (yeast strain) showing various phenotypes can be easily and efficiently bred by random mutagenesis of a proofreading- deficient mutant.

• Journal of Microbiology and Biotechnology
• /
• v.2 no.2
• /
• pp.108-114
• /
• 1992

The fermentative characteristics in ethanol production from lactose, with increased ethanol tolerance, of a fusant yeast strain constructed by protoplast fusion of Saccharomyces cerevisiae and Kluyveromyces fragilis were studied. The ethanol tolerance of this strain was increased to 8.0%, compared with the parent K. fragilis. During batch ethanol fermentation the optimal cultivation conditions for this fusant yeast were an initial pH of 4.5, a culture temperature $30^\circ{C}$. stirring at 100 rpm without aeration in 10% lactose medium (supplied with 1.0% yeast extract). Using this fusant strain in whey fermentation to ethanol, maximum ethanol production reached 3.41% (w/v) (theoretical yield; 66.7%) after a 48 hour cultivation period.