• Journal of Microbiology and Biotechnology
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• v.23 no.10
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• pp.1434-1444
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• 2013

We established a two-step production process using immobilized S. cerevisiae and P. stipitis yeast to produce ethanol from seaweed (U. pertusa Kjellman) hydrolysate. The process was designed to completely consume both glucose and xylose. In particular, the yeasts were immobilized using DEAE-corncob and DEAE-cotton, respectively. The first step of the process included a continuous column reactor using immobilized S. cerevisiae, and the second step included a repeated-batch reactor using immobilized P. stipitis. It was verified that the glucose and xylose in 20 L of medium containing the U. pertusa Kjellman hydrolysate was converted completely to about 5.0 g/l ethanol through the two-step process, in which the overall ethanol yield from total reducing sugar was 0.37 and the volumetric ethanol productivity was 0.126 g/l/h. The volumetric ethanol productivity of the two-step process was about 2.7 times greater than that when P. stipitis was used alone for ethanol production from U. pertusa Kjellman hydrolysate. In addition, the overall ethanol yield from glucose and xylose was superior to that when P. stipitis was used alone for ethanol production. This two-step process will not only contribute to the development of an integrated process for ethanol production from glucose-and xylose-containing biomass hydrolysates, but could also be used as an alternative method for ethanol production.

• KSBB Journal
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• v.9 no.5
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• pp.443-449
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• 1994

Fermentation characteristics of Kluyveromyces fragilis CBS 1555 with Jerusalem artichoke juice, in extractive ethanol fermentation in aqueous two phase systems composed of polyethylene glycol 20000 (PEG) and crude dextran(Dx), were investigated as a function of initial sugar concentrations, concentrations of ethanol formed, or fermentation time. Both specific ethanol production rate increased with decrease in concentrations of PEG and Dx in two-phase systems. Without being related to the compositions of aqueous two-phase system, maximum specific cell growth rate and maximum specific ethanol production rate were showed in the initial sugar concentration fo $80g/\ell$ and $120g/\ell$, respectively. The inhibition effects of ethanol on specific cell growth rate and specific ethanol production rate decreased with decrease in PEG concentration and in the range of 2.5 to 5% Dx. Specific cell growth rate and specific ethanol production rate was fitted as an exponential function and a hyperbolic function, respectively, of the concentrations of ethanol formed. Overall ethanol productivity increased with increase in initial sugar concentrations, and also the required time for the maximum productivity was so. Ethanol production rate by the elapsed fermentation time showed the maximum value in the initial sugar concentration of $160g/\ell$.

• Microbiology and Biotechnology Letters
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• v.28 no.3
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• pp.172-179
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• 2000

Bretlanomyces C!tstersii Hl-39 mutant was immobilized with various caniers. Immobilized mutant Hl-39 produced more ethanol and showed higher productivity and cell concentration than those of free 81-39 in 3.4% hydrolyzate of wood-chips at different temperatures ($37^{\circ}C$, $40^{\circ}C$ and $43^{\circ}C$). At $37^{\circ}C$, ethanol concentration produced by mutant H1-39 immobilized in Ca-alginate and ARG(l % Ca-alginate, 1.67% bentonite, 0.33% glutaraldehyde) bead were higher than those produced by the other earners (ACG ; 1 % CaHalginate. ] .67% celite R-634 , 0.33% glutaraldehyde, ABP ; 1 % Ca-alginate. 1.67% bentonite, 0.33% pectin. ACP: 1 % Ca-alginate, ] .67% celiLe R-634, 0.33% pecLin). The highest value of productivity(l.23 ) was obtained by using ABG beads. At $40^{\circ}C$, ethanol conccntration and productivity obtained by ABC beads ,>,"ere 15.2 glL and 0.84 gl L.h, respectively, which showed the highest value compared to other carriers. Particularly, productivity of ilmnobilized ceIl was increased up to 90% as compared to that offree cell. On the other hand, ABP(l % Ca-alginate+L67% bentonile+O.33% pectin) beads gave the best resulLs at $43^{\circ}C$ for production of ethanol and productivity, which were 13.8 g!l and 0.77 g/l h, respectively.ively.

• Journal of Life Science
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• v.29 no.1
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• pp.135-145
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• 2019

Zymomonas mobilis has been recognized as a potential industrial ethanologen for many decades due to its outstanding fermentation characteristics, including high ethanol tolerance, fast sugar uptake rate, and high theoretical ethanol yield. With the emergence of the postgenomic era and the recent announcement of DuPont's world largest cellulosic ethanol production process, research on this bacterium has become even more important to harness successful application not only for use in the bioethanol process but also in other biochemical processes, which can be included in bio-refinery. As an important industrial microorganism, Z. mobilis will likely be exposed to various stressful environments, such as toxic chemicals, including the end-product ethanol and fermentative inhibitory compounds (e.g., furan derivatives, organic acids, and lignin derivatives in pretreatment steps), as well as physical stresses, such as high temperature during large-scale ethanol fermentation. This review focuses on recent information related to the industrial robustness of this bacterium and strain development to improve the ethanol yield and productivity in the lignocellulosic ethanol process. Although several excellent review articles on the strain development of this bacterium have been published, this review aims to fill gaps in the literature by highlighting recent advances in physiological understanding of this bacterium that may aid strain developments and improve the ethanol productivity for lignocellulosic biomass.

• Microbiology and Biotechnology Letters
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• v.20 no.5
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• pp.607-613
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• 1992

A tower fermentor equipped with a modified settler was used for ethanol fermentation using highly flocculating yeast, Saccharomyces uvarum. The settler was constructed of glass column divided into two chambers by a funnel shaped divider. Gas was allowed to escape from lower chamber of the settler through a small tube. This design significantly reduced the turbulence in upper chamber of the settler and made it possible to operate at high dilution rate. Using the tower fermentor, the effects of operating conditions such as initial glucose concentration, dilution rate and cell recycle ratio were studied. The maximum ethanol productivity, 64.0 g/l' h was obtained at a dilution rate 1.1 h -1 and a cell recycle ratio 5 with the corresponding ethanol concentration of 58.8 g/l, and cell mass of 88 g/l.

• Microbiology and Biotechnology Letters
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• v.20 no.3
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• pp.324-328
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• 1992

In order to develop more economic processes, continuous ethanol fermentation from starchy raw materials in a pilot scale multi-stage CSTR was investigated. Ethanol fermentation could be successfully operated for 30 days with naked barley and 60 days with cassava, respectively. Starchy raw materials used for this study were ground and passed through a 20-mesh sieve for low temperature cooking. Under the optimized conditions, the overall productivity of cassava was $1.27g/{\ell}{\cdot}h$ with an ethanol concentration of 9.51% (v/v), which was higher about 2 times than that obtained from a conventional batch system in industrial scale.

• Journal of Hydrogen and New Energy
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• v.29 no.6
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• pp.648-653
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• 2018

Bran of barley causes high viscosity in bioethanol production due to the large amount of ${\beta}$-glucans and fiber. High viscosity is the main cause of decreased productivity and decreased facility efficiency in ethanol production. In order to prevent high viscosity, this study investigated the possibility of bioethanol from barley by debranning. As a result, it was able to reduced the viscosity (22.8 cP to 17.5 cP). And the fermentation speed and yield were improved as the activity of the enzyme and activity of yeast was also increased was improved due to the removal of non-fermentable components. In conclusion, debranning was advantageous in two ways. Firstly, bran removal increased the starch content of the feedstock and decreased viscosity of mash, improving ethanol fermentation. Secondly, by-products produced by debranning can use valuable products. It was remarkable results to the feasibility of bioethanol production from debranned barley.

• Journal of Microbiology and Biotechnology
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• v.4 no.4
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• pp.316-321
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• 1994

We investigated the possibility of industrial application and economit process of high temperature fermentation by thermotolerant alcohol producing yeasts as previously reported. From the 20% glucose media, the RA-74-2 produced 11.8% (v/v) ethanol at $32^{\circ}C$ (0.5% inoculum) and 10.6% (v/v) ethanol at $40^{\circ}C$ (3% inoculum), respectively. Also, 11.3% (v/v) ethanol was produced for 96 hours in the temperature-gradient fermentation. These results suggest that the RA-74-2 could isuccessfully be applied to save the cooling water and energy in industrial scale without re-investment or modification of established fermentation systems. When potato starch was used as the substrate for the RA-74-2, high temperature fermentation above $40^{\circ}C$ was more appropriate for industrial utilization because organic nitrogen was not necessary to economical fermentation. As the naked barley media just prior to industrial inoculation, taken from the Poongkuk alcohol industry Co., were used, 9.6% (v/v) ethanol was produced at $40^{\circ}C$ for 48 hours in jar-fermentor scale (actually, 9.5-9.8% (v/v) ethanol was produced at 30~$32^{\circ}C$ for 100 hours in industrial scale). The ethanol productivity was increased by the high glucoamylase activity as well as the high metabolic ratio at $40^{\circ}C$ Therefore, if the thermotolerant yeast RA-74-2 would be used in industrial scale, we could obtain a high productivity and saving of the cooling water and energy. Meanwhile, the RA-912 produced 6%(v/v) ethanol in 10% glucose media at $45^{\circ}C$ and showed the less ethanol-tolerance compared with industrial strains. As the produced alcohol was recovered by the vacuum evaporator at $45^{\circ}C$ in 15% glucose media, the final fermentation ratio was enhanced (76% of theoretical yields). This suggest that a hyperproductive process could be achieved by a continuous input of the substrate and continuous recovery of the product under vacuum in high cell-density culture.

• KSBB Journal
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• v.10 no.3
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• pp.231-236
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• 1995

For continuous ethanol production In an immobilized cell reactor consisting of Saccharomyces sake, feedings of one tenth to three tenths times diluted fermentation media were effective for maintaining the high ethanol productivity and physical stability of immobilized beads. In case two tenths times dilltued one of the fermentation medium supplemented with egg albumin hydrolysate(0.5%) and phosphatidylcholine(0.5%) was fed, a maximum ethanol productivity of $69 g/\ell$-hr was attained at a dilution rate of$1.1lhr^{-1}$, and it was 50% higher than that of the two tenths times diluted one of the fermentation medium without any supplement, $46 g/\ell$-hr.

• KSBB Journal
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• v.5 no.4
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• pp.335-339
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• 1990

In order to develop economic processes for ethanol production from starch, a simultaneous saccharification and fermentation(SSF) process using Zymomonas mobilis and amyloglucosidase (AMG) was studied in semibatch modes using cell recycle. The cell recycle was carried out by adopting two different methods; microfiltration and settling. The cell recycle using microfiltration revealed higher productivity(5.4 g/l/h) than that using a settler(4.3 g/l/h). Taking the large-scale ethanol fermentation into account, the semibatch process using microfiltration system appeared most promising among others with respect to ethanol productivity, feasibility of scale-up and simplification of operation.