• Food Science and Biotechnology
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• v.17 no.3
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• pp.558-563
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• 2008

To prevent weakly flocculating characters of bottom brewing yeast during first fermentation, various technical investigations were carried out using strain of Saccharomyces cerevisiae. It appeared that the propagation at $10^{\circ}C$ promoted the molecular structure and biochemical composition of cell wall in favor of flocculation. The yeast grown at $20^{\circ}C$ by addition of zinc ion also had a stimulating effect on flocculation behavior during first fermentation cycle. The zinc ion did not influence directly on the changes of cell wall in favor of stronger flocculence. The increased fermentation activity of yeast due to addition zinc ion was rather responsible for the intensified flocculation capacity. It was concluded that the weakly flocculating characters of bottom brewing yeast during first fermentation can be solved by using yeast propagated at $10^{\circ}C$ or by means of yeast by addition of zinc ion during propagation.

• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.419-424
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• 2018

In this work, effect of the culture medium composition on the fermentation process of Clostridium ljungdahlii, which is acetogenic bacteria to product ethanol from synthesis gas, was examined to improve the microbial growth and ethanol production. Components of the culture medium such as yeast extract, fructose, $NH_4Cl$, and $K_2HPO_4$ were selected as influence factors for the cell growth and ethanol production. As the concentration of yeast extract increased, both of the cell growth and ethanol production increased. And the ethanol productivity was the highest at an yeast extract of 0.05 g/L, which is lower than that of base medium. As the concentration of fructose increased, the cell growth increased, but the ethanol production decreased when the concentration of fructose was higher than that of base medium (5 g/L). In an experiment with the yeast extract of 5 g/L, produced ethanol concentration was the highest (0.297 g/L) when fructose concentration was 5 g/L, however, the specific ethanol productivity was higher (0.281 g/g DCW) when the fructose was not added due to very low cell mass. The cell growth and ethanol production were not significantly influenced by $NH_4Cl$ concentration, however the growth inhibition was observed at a 30 g/L of $NH_4Cl$. When the concentration of $K_2HPO_4$ increased, both of the cell growth and ethanol production increased. In experiments with $NH_4Cl$ and $K_2HPO_4$, specific ethanol productivities were higher when the low concentration of yeast extract was used.

• Korean Journal of Microbiology
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• v.43 no.3
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• pp.217-221
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• 2007

The domestic cultured Campbell's Early and Geubong grapes were fermented far the production of red wines with the isolated wild yeast Saccharomyces cerevisiae IJ850. For the isolation of wild yeast, Geubong and Campbell's Early grapejuices were naturally fermented at room temperature for 6 days without adding stater culture. The strain isolated from Geubong which has 1.8 times higher fermentative ability than the strains isolated Campbell Early was selected. The selected strain was identified by using 26S rDNA sequencing. The strain showed 99.7% of similarity with Saccharomyces cerevisiae and thus identified as Saccharomyces cerevisiae IJ850. It was investigated the fermentative ability as the start culture. For the production of grapewine, the final sugar concentrations of grapejuices were adjusted to the $25^{\circ}Brix$ with anhydrous glucose. The grapejuices were fermented at room temperature for 10 days in the air-locked bottles filled with $CO_2$ gas. The final yield and alcohol concentration of Campbell's Early and Geubong grapewines fermented with the isolated wild yeast were 80.8%, 11.0% and 87.8%, 13.0%, respectively. Between the isolated wild yeast S. cerevisiae IJ850 and the commercial yeast S. cerevisiae EC1118, total acidities of grapewines produced with wild yeast were lower than those produced with the commercial yeast. The pH values and the values of color analysis of grapewines produced with both strains were similar. The total phenol contents of campbell's Early and Geubong wines produced with the isolated yeast and the commercial yeast were obtained in the range of 75 to 125mg/L. In conclusion, S. cerevesiae IJ850 isolated from the domestic cultured Geubong grape is able to use to produce grapewines as stater culture.

• Microbiology and Biotechnology Letters
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• v.25 no.3
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• pp.311-316
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• 1997

A high xylitol producing yeast was isolated from the sludge of xylose manufacturing factory and then identified as Candida tropicalis DS-72 according to physiological properties. The strain was able to produce xylitol in a high concentration up to 72g/l from 100g/l xylose in 32 hours. Medium optimization for xylitol production by C. tropicalis DS-72 was performed. Effect of various nitrogen sources on xylitol production was investigated. Of nitrogenous compounds, yeast extract was the most suitable organic nitrogen nutrient for the enhancement of xylitol production. However, inorganic nitrogen resulted in a low cell concentration and did not produce xylitol. Effect of inorganic salts such as KH$_{2}$PO$_{4}$, and MgSO$_{4}$, 7H$_{2}$O on xylitol production was also studied. Optimal medium was selected as xylose 100g/l, yeast extract 10g/l, KH$_{2}$PO$_{4}$, 5 g/l and MgSO$_{4}$, 7H$_{2}$O 0.2 g/l. Xylitol of 88 g/l was produced from 100 g/l xylose in 30 hours using the optimal medium in a flask. In a fermentor, a fed-batch culture with 300g/l xylose was carried out. A final xylitol concentration of 240 g/l in the culture could be obtained in 43 hours of culture time by maintaining the high level of dissolved oxygen during growth phase and limiting the dissolved oxygen in the same culture during production phase. This result corresponded to a xylitol yield of 80% and a xylitol productivity of 5.58 g/1-h.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.1
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• pp.23-28
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• 2005

Lactic acid is a green chemical that can be used as a raw material for biodegradable polymer. To produce lactic acid through microbial fermentation, we previously screened a novel lactic acid bacterium. In this work, we optimized lactic acid fermentation using a newly isolated and homofermentative lactic acid bacterium. The optimum medium components were found to be glucose, yeast extract, $(NH_4)_{2}HPO_4,\;and\;MnSO_4$. The optimum pH and temperature for a batch culture of Lactobacillus sp. RKY2 was found to be 6.0 and $36^{\circ}C$, respectively. Under the optimized culture conditions, the maximum lactic acid concentration (153.9 g/L) was obtained from 200 g/L of glucose and 15 g/L of yeast extract, and maximum lactic acid productivity ($6.21\;gL^{-1}h^{-1}$) was obtained from 100 g/L of glucose and 20 g/L of yeast extract. In all cases, the lactic acid yields were found to be above 0.91 g/g. This article provides the optimized conditions for a batch culture of Lactobacillus sp. RKY2, which resulted in highest productivity of lactic acid.

• KSBB Journal
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• v.14 no.2
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• pp.181-187
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• 1999

We have investigated industrial media for lactic acid fermentation to reduce the cost of nitrogen sources. Corn steep liquor (CSL) was successfully used at 5% (v/v) in batch fermentations. Use of soluble CSL improved the productivity about 20% with an advantage of clearer fermentation broth. Yeast extract-complemented CSL improved the productivity about 20% with an advantage of clearer fermentation broth. Yeast extract-complemented CSL media further increased the increased the productivity. It was found that 3.1 g/L yeast extract and 5% CSL could be an effective substitute for 15 g/L yeast extract in 10% glucose medium. Brewing yeast was also used as a sole nitrogen source equivalent to 5% CSL. A continuous culture coupled with cell-recycle by microfiltration at the dilution rate of 0.05-0.065 h-1 led to the highest lactic acid productivity. Lactic acid was recovered by electrodialysis from the cell free broth. Depleted cell free broth supplemented with 5-10 g/L of yeast extract performed reasonably in batch and continuous cultures. Reuse of the fermentation broth may reduce the cost of raw materials as well as minimize the fermentation wastes.

• Biotechnology and Bioprocess Engineering:BBE
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• v.5 no.4
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• pp.288-305
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• 2000

A review on the main aspects associated with yeast flocculation and its application in biotechnological processes is presented. This subject is addressed following three main aspects-the basics of yeast flocculation, the development of "new" flocculating yeast strains and bioreactor development. In what concerns the basics of yeast flocculation, the state of the art on the most relevant aspects of mechanism, physiology and genetics of yeast flocculation is reported. The construction of flocculating yeast strains includes not only the recombinant constitutive flocculent brewer's yeast, but also recombinant flocculent yeast for lactose metabolisation and ethanol production. Furthermore, recent work on the heterologous $\beta$-galactosidase production using a recombinant flocculent Saccharomyces cerevisiae is considered. As bioreactors using flocculating yeast cells have particular properties, mainly associated with a high solid phase hold-up, a section dedicated to its operation is presented. Aspects such as bioreactor productivity and culture stability as well as bioreactor hydrodynamics and mass transfer properties of flocculating cell cultures are considered. Finally, the paper concludes describing some of the applications of high cell density flocculating bioreactors and discussing potential new uses of these systems.e systems.

• Journal of the Korean Society of Food Culture
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• v.6 no.2
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• pp.141-146
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• 1991

This is a study about Jangs presented in the Cheminyosul. Scattered yeast and purified salts are used as ingredients of Jangs. Hwangeui, Hwangjeung and Eol are scattered yeast, and Sangmanyom, Hwayom and Inyom are purified salts. According to their main ingredient, Jang can be classified Kokjang, Yukjang and Eojang. Kokjang was made from soybean and/or wheat, Yukjang made from meat, and Eojang made from fish and crustacea. Eojang is similar to Korean fish sauce, Jeot. Three kinds of Kokjang, four kinds of Yukjang and seven kinds of Eojang are described in the Cheminyosul. Generally, Jangs were fermented and ripened for one day to one hundred days. Also, most of Jangs were made in cold season except Keonjeeojang and Janghae.

• Korean Journal of Food Science and Technology
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• v.9 no.2
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• pp.97-105
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• 1977

1) In order to obtain a microbial strain having a strong yeast cell wall lytic activity, about 156 isolates capable of forming clear zones on baker's yeast-peptone-bouillon agar plate were obtained from soil, mud and water samples and a strain K-42 with the highest lytic activity was identified as Bacillus circulans. 2) Effect of carbon sources on the lytic enzyme production by the K-42 strain was in the decreasing order of maltose>glucan>xylose>control in 2-day culture and of lactose>galactose>glucan>control in 3-day culture. Effect of inorganic nitrogen sources was in the decreasing order of ammonium acetate>sodium nitrate>control in 2-day culture and of ammonium chloride>ammonium oxalate>control in 3-day culture, whereas organic nitrogen sources except milk casein showed an increase in 2-day culture and a decrease in 3-day culture. Synergistic effect of carbon sources and nitrogen sources was not observed. 3) The enzyme production by the K-42 strain was greatly affected by pH change of the culture medium, thus a high lytic activity could be maintained by keeping the pH range of $7{\sim}8$ and adding carbon or nitrogen sources. 4) Optimum conditions for the lytic activity of the K-42 strain were obtained at $pH\;7{\sim}8$ and $60^{\circ}C$ and the extent of hydrolysis toward heated yeast cell wall was 65%.

• KSBB Journal
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• v.8 no.5
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• pp.495-503
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• 1993

To investigate the characteristics of growth and oil production of peppermint cells during a batch culture, cells derived from peppermint callus was cultivated in an air bubble reactor. During the batch culture, effects of inoculum size, abiotic stress, yeast elicitor, and two stage culture on the cell growth, the productivity of oleolesin, and the formation of flavor components were determined and also the sugar concentrations and kinetics of cell growth were analyzed. Among the various sizes of inoculum, the culture with 2.0% packed cell volume inoculum showed the optimum condition for cell growth in the proposed bioreactor, and the cell yield and essential oil production reached to 5.7g/1 and 0.109g/1, respectively. When the abiotic stress of daily 8hr dark and $10^{\circ}C$ cold treatments were given to the culture cell growth decreased but essential oil production increased to 0.546g/l. In a modified Lin-Staba medium in which 100mg/l yeast extract as an elicitor was added to the culture, the cell growth and oil production increased, and menthol content was 22.5% of oil. In the two stage culture, in which the basic culture conditions of 27$^{\circ}C$, light, and without elicitor were employed during the first six days followed by the second stage with daily 8hr treatment of cold and dark condition, and also with yeast extract as an elicitor, cell growth decreased after eight days, essential oil production was not increased, and menthol was not detected. Dry cell yield was 0.38g dry cell/g sugar and specific growth rate was 0.25 day-1. The major terpenoid in the oil was not the menthol but pulegone and piperitone, precursors of menthol were accumulated. However, when yeast elicitor was added, menthol was produced to the level of 22.5% which was the highest value in the peppermint cell culture reported so far.