• Microbiology and Biotechnology Letters
• /
• v.47 no.4
• /
• pp.565-573
• /
• 2019

Production of biofuels and value-added materials from cellulosic biomass requires the development of a microbial strain capable of efficiently fermenting mixed sugars. In this study, the natural xylose fermenting yeast, Pichia stipitis, was evolved to simultaneously ferment cellobiose and xylose. Serial subcultures of wild-type P. stipitis in 20 g/l cellobiose were performed to increase the rate of cellobiose consumption. A total of ten rounds of the serial subculture led to the isolation of an evolved strain fermenting cellobiose significantly faster than the parental strain. The evolved strain displayed enhanced ethanol yield from 0 to 0.4 g ethanol/g cellobiose. The evolved P. stipitis simultaneously fermented cellobiose and xylose in batch fermentation. The genetic information of our evolved P. stipitis would be valuable in the development of a microbial host for the production of biofuels and biomaterials from cellulosic biomass.

• Microbiology and Biotechnology Letters
• /
• v.26 no.1
• /
• pp.34-39
• /
• 1998

We have already prepared a human lysozyme (HLY) structural gene from chemically synthesized 38 oligomers with high codon usage in Saccharomyces cerevisiae. For directing the synthesis and secretion of HLY in S. cerevisiae, two types of expression vectors, a YCp centromere-based vector, pHK101 and a YEp 2-$\mu\textrm{m}$ circle-based vector, pHK501 were constructed. With the resulting plasmids, we have confirmed that yeast transformant harboring pHK501 has more secreted HLY than pHK101-transformant by using a lysoplate and a turbidimetric assay. In flask cultivation, pHK501-transformant produced active HLY about 8 times (55 units/$m\ell$) higher than pHK101-transformant. From batch cultivation, the HLY productivity was obtained with 1.12 units/$m\ell$/h, corresponding to a 1.8-fold increase compared with flask fermentation. These results indicate that yeast transformant with pHK501 vector overexpressed and secreted HLY than that of YCp type vector.

• Korean Journal of Food Science and Technology
• /
• v.35 no.3
• /
• pp.455-460
• /
• 2003

Effects of 0.25 and 0.5% citric and phytic acids on color and quality properties of doenjang during fermentation at $30^{\circ}C$ for 80 days were evaluated. As concentration of organic acid and fermentation time of acid-added doenjang increased, acidity, lightness, and antibrowning rate increased, whereas pH, amino nitrogen, and enzyme activity decreased compared to nonacid-added control. Microbial populations of total bacteria, yeast, and lactic acid bacteria were not affected by decrease in pH. Although degree of brown color (p<0.05) could be differentiated, flavor, palatability, acid taste, and overall preference were not significantly different. Browning of doenjang added with 0.25% of either organic acid was inhibited, while quality properties and sensory characteristics were similar to those of the control.

• Korean Journal of Food Science and Technology
• /
• v.32 no.5
• /
• pp.1135-1141
• /
• 2000

For investigation of new utilization as jang-products, Meju was prepared using barely bran. As barley meju was fermented, change of pH was $5.2{\sim}5.6$, it was indistinguishable change. L-value of color was changed from 46.9 to 60.3, that meant it was getting moe dark. The counts of aerobic bacteria were $4.8{\times}10^7{\sim}5.6{\times}10^9$ CFU/g, it was extraordinarily increased during fermentation. Counts of Yeast, molds, and bacteria were $9.1{\times}10^6{\sim}5.0{\times}10^8$ CFU/g, $8.3{\times}10^5{\sim}6.9{\times}10^7$, and $2.0{\times}10^2{\sim}4.5{\times}10^6$ CFU/g, respectively. Crude ash content was $3146.0{\sim}7147.4$ mg%. The level of K was the highest in quantity among the crude ash in barely meju. 7 free sugars(i.e., raffnose, stachyose, inositol, fructose, glucose, arabinose, and maltose), 3 volatile organic acid(i.e., acetic acid, propionic acid, and butyric acid) and 4 non-volatile organic acid(i.e., fumaric acid, ${\alpha}-ketoglutaric$ acid, malic acid, and citric acid) were detected. The content of free amino acid was $596.3{\sim}1580.8$ mg%. Glutamic acid was most abundant component among the amino acids, 2nd abundant component was alanine, it's content was $79.9{\sim}165.3$ mg%, 3rd abundant component was leucine, it's count was $41.7{\sim}161.6$ mg%. Finally, essential amino acid content was revealed $33.2{\sim}40.38%$.

• Applied Biological Chemistry
• /
• v.43 no.4
• /
• pp.277-284
• /
• 2000

In order to investigate the changes of microorganisms, enzyme activity and physiological functionality of five types of traditional Deonjang prepared with various concentrations of Lentinus edodes. The pH of traditional Deonjang was decreased but total acidity was increased during fermentation. NaCl concentrations was increased up to $15.67{\sim}16.02%$ until $30{\sim}45$ days of fermentation but decreased after that. Amino acidity was increased on the traditional Deonjang with increasing the mixture ratio of Lentinus edodes. Reducing sugar content was increased up to $30{\sim}45$ days of fermentation. Total sugar content was increased up to $18.21{\sim}20.57%$ until 30 days of fermentation. As the mixing ratio of Lentinus edodes increased, total sugar also increased. The number of bacteria was highest in all sample after 45 days fermentation, while that of mold was decreased during fermentation. Amylase activity was decreased but protease activity, tyrosinase inhibitor and ACE inhibitor were increased on the traditional Doenjang with increasing the mixture ratio of Lentinus edodes. Antimutagenic activities of traditional Deonjang (10% Cortinellus edodes) were 83.15%, 65.88% against MNNG, NPD on S. typhimutium TA100 and 54.59%, 55.00% against NQO, NPD on S. typhimutium TA98

• KSBB Journal
• /
• v.14 no.4
• /
• pp.476-481
• /
• 1999

S. cerevisiae mutant(reg1-501, gal1), which cannot use galactose and has alleviated glucose repression level, is used as host for optimizing induction of GAL promoter. The optimum concentration of galactose as inducer for recombinant protein production and the galactose consumption rate have been tested with S. cerevisiae mutant and compared with conventional S. cerevisiae. The extent of glucose repression were investigated for both strain and the degradation pattern of produced foreign protein have been compared in both cases. The effect of pH on foreign protein degradation pattern were studied for both strains. The secetion efficiency of both strains were carried out. Through these experiments, optimum condition of recombinant protein production by GAL promoter using S. cerevisiae mutant (reg1-501, gal1) were found.

• Korean Journal of Food Science and Technology
• /
• v.54 no.2
• /
• pp.196-202
• /
• 2022

In this study, the quality characteristics of Jeung-pyun with different amounts of Makgeolli (50, 100, 150, and 200 mL) were investigated, and standardization of the Jeung-pyun production process is suggested. Higher Makgeolli contents resulted in an increase in Jeung-pyun qualities such as the b value, air cell size, springiness, and cohesiveness, whereas Jeung-pyun characteristics such as the L values, pH, number of air cells, hardness, and gumminess significantly decreased. The specific volume was highest following method M-150, and the expansion rate was lowest following method M-200. Altering the Makgeolli content did not significantly differ in moisture content and b values. In the sensory evaluation results, the M-150 method produced the highest-ranking results for all tested items (i.e., overall acceptability, appearance, flavor, taste, and texture). Therefore, this study suggests that Jueng-pyun produced with the M-150 mixing ratio has excellent quality and sensory characteristics. Furthermore, the results of this study can be used as preliminary data for the standardization of Jueng-pyun production.

• Journal of Life Science
• /
• v.17 no.9 s.89
• /
• pp.1248-1254
• /
• 2007

The secretory overexpression of Clostridium thermocellum endoglucanase A gene (celA) was examined in Saccharomyces cerevisiae using Kluyveromyces marxianus exoinulinase (INU1) signal sequence and GAL10 promoter. The two plasmids, pYEG-CT1 with its own signal sequence, and pYInu-CT1 with INU1 signal sequence were introduced to S. cerevisiae SEY2102 and S. cerevisiae 2805 host strains, respectively, and then each transformant was selected on the synthetic defined media lacking uracil. The expression level and secretion efficiency of endoglucanase A was increased by $18{\sim}22%$ and 11%, respectively, by INU1 signal sequence over celA signal sequence. By considering the high level of expression (361 unit/I), plasmid stability (89%), and secretion efficiency (70%), S. cerevisiae 2805 harboring plasmid pYInu-CT1 was selected as the opti-mal host vector system for the production of cellulose-degrading enzyme and recombinant yeast probiotic. The total expression and secretion efficiency of endoglucanase A was 418 unit/l and 73%, respectively, in the batch fermentation of S. cerevisiae 2805/pYlnu-CT1 on galactose medium. The mo-lecular weight of secreted endoglucanase A was found to be greater than 100 kDa, presumably due to the N-linked glycosylation.

• Microbiology and Biotechnology Letters
• /
• v.30 no.1
• /
• pp.68-72
• /
• 2002

To obtain a yeast mutant with high RNA content and high growth rate, Saccharomyces cerevisiae MTY62 was mutated with ethylmethane sulfonate. Among the selected mutants that were sensitive to the high concentration of KCl, M40-10 strain was finally selected due to its rapid cell growth and high RNA content in the tube and baffled-flask cultures. In the batch culture of M40-10 mutant, the maximum specific growth rate ($\mu_{max}$) of $0.38 h^{-1}$ , RNA concentration of 3210 mg-RNA/1, and RNA content of 183 mg-RNA/g-DCW were obtained, which were 23%, 15%, and 12% increased levels, respectively, compared to those of MTY62 parent strain. The intermittent fed-batch culture of M40-10 strain resulted in the maximum cell concentration of 35.6 g-DCW/1, RNA concentration of 5677 mg/1, and RNA content of 160 mg-RNA/g-DCW. Through the constant fed-batch culture, the maximum cell concentration of 46.4 g-DCW/1, RNA concentration of 6270 mg-RNA/1, and RNA content of 135 mg-RNA/g-DCW were obtained. At the 20 h culture time in the fed-batch cultures of M40-10 strain, the cell and RNA concentrations were increased by 30% and 10%, respectively, over the parent strain MTY62. In addition, it was also found that the accumulated RNA within the mutant cell was not degraded until the end of fed-batch cultivation, indicating that the M40-10 cell is a mutant with weak acidic RNase activity.y.

• Food Engineering Progress
• /
• v.13 no.2
• /
• pp.110-116
• /
• 2009

Gochujang, a fermented traditional Korean hot pepper-soybean paste, has long been used to provide hot, sweet, and savory tastes. Changes in the pH, titratable acidity, moisture content, water activity, amino-nitrogen content, NaCl content, color, and yeast population during aging were investigated using a model system of Gochujang incorporated with strawberry puree up to 14% as a value-added food ingredient. pH decreased slowly till 60 days of aging then increased afterwards. Titratable acidity, on the other hand, increased during aging, reaching at the highest level at the 60 days of aging and then decreased rapidly. The moisture content continually increased during aging up to 90 days whereas water activity decreased rapidly till 60 days of aging and then slightly increased. The amino-nitrogen content increased while NaCl content decreased continually during aging. All the color parameters including L$^{*}$, a$^{*}$, and b$^{*}$-values increased during aging in general with exception for b$^{*}$-values in some conditions. Initial yeast population was ranged 1.2-4.9${\times}10^{6}$CFU/g and increased to 1.1-5.9${\times}10^{7}$CFU/g after 90 days of aging.