• Microbiology and Biotechnology Letters
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• v.17 no.1
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• pp.14-18
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• 1989

As the final experiment to assess the possibility of industrial application of FSC14-75, ethanol productivity from liquefied sweet potato starch was examined in a pilot scale of 300 liters. FSC14-75 produced 6.6％(v/v) of ethanol from 13.3％ of liquefied sweet potato starch in 8 days, and the residual sugar was 3.15％. The corresponding efficiency was 70％ of the theoretical maximum. Since we could isolate unicellular cell and flocculent cell from the fermentation broth, we designated them FSC14-75(S) and FSC14-75(F), respectively. We investigated ethanol productivity of FSC14-75(F) compared with that of FSC14-75(S) from liquefied potato starch in a mini·tar tormentor scale of 2.5 liters. FSC14-75(F) was found more favorable than the counterpart in terms of ethanol productivity, and produced 8.1％(v/v) of ethanol from 15％ of liquefied potato starch with an efficiency of 75％. In a pilot scale fermentation with 15％ of liquefied sweet potato starch, ethanol productivity of FSC14-75(F) reached maximum level of 7.7％(v/v) after 8 days, and the residual sugar was 1.9％. However, the ethanol productivity was not enhanced by a supplementary addition of Thermamyl to the fermentation broth after sterilization.

• Microbiology and Biotechnology Letters
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• v.49 no.2
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• pp.210-216
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• 2021

This study aimed to enhance ethanol productivity of Saccharomyces cerevisiae through genome editing using CRISPR/CAS9. To increase ethanol productivity, ACC1, ELO1, and OLE1 were overexpressed in S. cerevisiae using the CRISPR/CAS9 system. The strains overexpressing ACC1, ELO1, and OLE1 survived up to 24 h in YPD medium supplemented with 18% ethanol. Moreover, the ethanol yields in strains overexpressing ACC1 (428.18 mg ethanol/g glucose), ELO1 (416.15 mg ethanol/g glucose), and OLE1 (430.55 mg ethanol/g glucose) were higher than those in the control strains (400.26 mg ethanol/g glucose). In conclusion, the overexpression of these genes increased the viability of S. cerevisiae at high ethanol concentrations and the ethanol productivity without suppressing glucose consumption.

• KSBB Journal
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• v.4 no.1
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• pp.11-14
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• 1989

A study on the continuous fermentation with cell recycle by a tower fermentor to produce ethanol has been carried out. ethanol fermentation was conducted with flocculating yeast strain, Saccharomyces cerevisiae TS4, to compare the ethanol productivity with conventional continuous process. Employing a 15% glucose feed, a cell density of 50 g/l was obtaind. The ethanol productivity of the cell recycle system was found to be 26.5g EtOH/1-hr, which was nearly 7.5 times higher than the conventional continuous process without cell recycle. A cell recycle ratio of 7 to 8 resulted in the highest ethanol productivity and cell concentration. Thus the cell recycle ratio was found to be a key factor in controlling the production of clarified overflow liquid. An aeration rate above 3.8 $\times$ 10-3 VVM seemed to decrease the ethanol productivity. The continuous fermentation with cell recycle was successfully used in the separation of cells from fermentation broth with enhancement of mixing in the tower fermentor.

• Microbiology and Biotechnology Letters
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• v.17 no.1
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• pp.8-13
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• 1989

The optimum conditions for ethanol fermentation and ethanol productivity of the fusant ESC-14-15 were examined in a mini-jar formentor scale (working volume : 2.5 liters) to assess the possibility of practical application. Addition of yeast extract to fermentation broth greatly enhanced the ethanol productivity and shortened the period of fermentation. The pH 4.2 was more favorable than pH 5.5 with respect to ethanol productivity and fermentation speed. The optimum concentration of liquefied potato starch for ethanol fermentation of FSC-14-15 was 15%(w/v) and the corresponding productivity was 8.7%(v/v) of ethanol with an efficiency of 80.6% to the theoretical maximum. When the fresh fermentation broth containing 20% of liquefied potato starch was inoculated with love(v/v) of inoculum, the fusant FSC-14-75 produced 11.0%(v/v) of ethanol in 4 days, which is considered comparable to that from an industrial process. From the liquefied cassava starch or the equal mixture of liquefied barley and sweet potato starch prepared according to the same method as in the industrial process except saccharification step, the fusnnt FSC-14-75 produced 8.5%(v/v) or 7.6%(v/v) of ethanol in 4 days, respectively.

• Microbiology and Biotechnology Letters
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• v.16 no.6
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• pp.494-498
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• 1988

The optimum conditions for glucoamylase production, and ethanol productivity of the transformant TSD-14 were investigated as compared with the parental strains. The properties of TSD-14 were comparatively similar to the donor S. diastaticus IFO 1046 as regards the conditions of glucoamylase production and ethanol productivity. The soluble starch was the most effective carbon source for the glucoamylase production. While inorganic nitrogen sources did not prompt cell growth and enzyme production, the organic nitrogen sources generally enhanced both cell growth and glucoamylase production. The metal salts such as FeSO$_4$, MgSO$_4$, MnCl$_2$, and NiSO$_4$were favorable to the enzyme production. And the optium temperature and initial pH for glucoamylase production were 3$0^{\circ}C$ and 5. The transformant TSD-14 produced 8.3%(v/v) ethanol from 15% sucrose medium, 4.8%(v/v) ethanol from 15% soluble starch medium, and 7.5%(v/v) ethanol from 15% liquefied potato starch medium. The corresponding fermentation efficiency were 84% , 45% and 70%, respectively.

• KSBB Journal
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• v.4 no.2
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• pp.74-77
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• 1989

To increase the volumetric productivity a contimuous cell-recycled system was implemented. Cell concentrations between 9.2 and 15.0 g/1 were obtatined in the continuous fermentor study. At a 4% xylose feed and a specific oxygen supply rate(SOSR) of 1.04 g O2.hr-g DCW the ethanol yield was 0.36% at dilution rate. This represented a 26-% increase over that of th batch fermentation.

• Microbiology and Biotechnology Letters
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• v.20 no.5
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• pp.588-596
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• 1992

The fermentation characteristics of ethanol production by the use of immobilized Zymomonas mobilis KCTC 1534 cells were investigated in terms of formation factors such as substrate and product concentration. In batch fermentation, the maximum values of specific ethanol productivity, specific substrate uptake rate, ethanol yield, and glucose conversion rate were $29.14g/{\ell}{\cdot}h$, $60.24g/{\ell}{\cdot}h$, 0.48g/g, and 98.4%, respectively, with 17% glucose medium, and its ethanol productivity was $2.91g/{\ell}{\cdot}h$ in the case of 25 hour fermentation time. Repeated batch fermentation was possible for 30 days with 2.24-$2.94g/{\ell}{\cdot}h$ ethanol productivity. In semicontinuous fermentation, the maximum ethanol productivity was shown to be $15.7g/{\ell}{\cdot}h$ at $0.36h^{-1}$ effective dilution rate with 17% glucose concentration. In this case, ethanol yield coefficient and glucose conversion rate were 0.39 g/g, 64.7%, respectively.

• Microbiology and Biotechnology Letters
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• v.23 no.6
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• pp.723-729
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• 1995

A flocculating sugar tolerant yeast strain was isolated from fermenting Takju. This strain was identified as Saccharomyces cerevisiae CA-1 according to the Lodder's yeast taxonomic studies. The isolated yeast could grow in 50% glucose and in 7% ethanol in the YPD medium. It's optimal growth temperature, initial pH, shaking rate and initial glucose concentration for ethanol fermentation showed 35$\circ$C, 4.5, 150 rpm, 15%, respectively. Ethanol concentration was 63 g/l in 20% glucose after 24 hours, fermentation yield was 0.49 g-ethanol/g-glucose in 10% glucose after 24 hours and ethanol productivity was 3.09 g/l$\cdot $h in 10% glucose after 12 hours in batch fermentation. Repeated batch fermentation was possible for over 50 days and ethanol yield, ethanol productivity and substrate conversion rate were 0.39-0.50 g/g, 1.63-2.08 g/l$\cdot $h and more than 99%, respectively during these periods.

• Microbiology and Biotechnology Letters
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• v.19 no.4
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• pp.419-427
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• 1991

Ethanol fermentation of glucose by a strain of Saccharomyces cereuisiae was studied in membrane recycle bioreactor, where the fermentation vessel was coupled with cross flow hollow fiber membrane. The cell recycle system controlled backflushing with fresh medium was proven to be effective in alleviating membrane fouling and allowing long term operation of high-cell continuous fermentation. Using 100 g/l initial glucose concentration, the maximum productivity of about 9 5 g/$l \cdot h$ has been achieved at dilution rate 2.5 $h^{-1}$ and bleed stream ratio 0.05 with the corresponding ethanol concentration of 35g/l and glucose conversion of 100%. Increasing the glucose concentration to 200 g/$l \cdot h$ resulted in an increase in ethanol concentration to 48 g/l and productivity to 120 g1l.h. Substrate conversion, however, was only 69%. This productivity was the highest value in the study, and about 38 fold more than that of batch culture and 17 fold more that of single stage continuous culture without cell recycling. No further increase in the productivity was obtained when the glucose concentration was increased reased to 300g/l.

• Microbiology and Biotechnology Letters
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• v.19 no.4
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• pp.319-324
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• 1991

Three strains able to efficiently produce ethanol from cellulosic hydrolysates were isolated from soil samples by enrichment culture in liquid saccharified wheat bran medium. The profiles of physiological and biochemical properties of two yeasts KM-09 and KM-402 and a bacterium Hg-225 were almost identical from those of Candida sp. and Klebsiella sp., respectively. Strains KM-09 and HG-225 used xylose and cellobiose as fermentable sugars, and HG-225 had a wide range of sugar utilization for ethanol fermentation. The optimal pH and temperature for growth of KM-09, KM-402 and HG-225 were 5.8, 5.6 and 6.8 and 32t, $30^{\circ}C$~ and $38^{\circ}C$, respectively. During the ethanol fermentation in saccharified wheat bran by the isolated strains, optimal temperature for ethanol production was more or less higher than those for growth, and addition of 0.2% (w/v) $MgSO_4$, into the medium enhanced ethanol productivity. Of the three strains ethanol content of KM-09 was the highest with about 2.3% (v/v), and ethanol production rate of HG-225 was faster than the others and maximum productivity was after 4 days. KM-09 (1.42% v/v) and HG-225 (1.05%, vlv) produced ethanol from 4% (wIv) xylose but growth rate was slower than on glucose. Otherwise KM-402 showed the highest ethanol productivity on glucose, but no ethanol was detected on xylose and cellobiose.