• Nonlinear Functional Analysis and Applications
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• 제27권3호
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• pp.569-585
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• 2022

A brief comparative survey of some generalizations of a metric space with three dimensional metric structures and different forms of the triangle inequality is done along with their topological properties. Then a common fixed point is obtained for reciprocally continuous and compatible self-maps in a G-metric space. Further, a common fixed point theorem is proved for a pair of weakly compatible self-maps on a G-metric space with the common limit range property.

• 한국미생물·생명공학회지
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• 제19권4호
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• pp.419-427
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• 1991

에탄올의 발효 생산성을 높이기 위해서는 발효조의 균체농도를 높여 고농도의 배양을 해야하며 또한 에탄올에 의한 저해 작용을 감소시켜 비생산성을 향상시키기 위해서는 발효액 중에 축적되는 에탄올을 배출 시킬 필요가 있다. 이와 같은 목적으로 본 연구에서는 고분자 hollow fiber membrane, ceramic filter를 이용하여 가장 중요한 조작 변수인 희석율과 bleed stream ratio가 에탄올 생산성에 미치는 영향 및 조작의 문제점과 장기 조업 가능성을 검토하였다.

• 생명과학회지
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• 제16권6호
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• pp.938-941
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• 2006

Continuous fermentation process for the production of soluble glucan using mutant Agrobacterium sp. ATCC31750 has been developed in this research. When the concentration of soluble glucan was higher than 6 g/l, the viscosity of the fermented broth was too high and it needs complex separation process to separate from culture broth. Mathematical models which describe the cell growth and glucan production was developed and they kinetic parameters were estimated with experimental data. They are used for the optimization of continuous fermentation process and calculate optimal dilution rate for easy separation of glucan 4 g/l. With continuous fermentation, glucan production rate was increased 1.8 times more than that with batch fermentation.

• KSBB Journal
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• 제4권1호
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• pp.11-14
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• 1989

Tower fermentor를 이용한 연속 알콜발효에서 cell re-cycle과 aeration에 대한 영향을 검토하였다. 균주는 floc-culationg 효모인 Saccharomyces cerecisiae TS4를 를 사용하였다. 15% glucose를 사용한 cell recycle system의 연속 알콜발효에서 cell 농도는 50%/1였고, ethanol productiv는 26.4g EtOH/l-hr로서 cell농도가 가장 높은 값을 나타내었으며, aeration rate는 3.8$\times$ $10^-^3$ VVM이상부터는 ethanol pro-ductivity가 감소하였다.

• KSBB Journal
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• 제11권1호
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• pp.58-64
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• 1996

K-carrageenan에 고정화시킨 Zymomonas mobilis를 이용한 연속적인 sorbitol 생산에 대하여 연구하였다. Toluene과 glutaraldehyde로 처리하여 투과성을 증대시킨 세포를 alginate나 chitin 고정화 공정에서 어느 정도의 효소활성을 보였으나 210시간 이상의 공정반응에서는 sorbitol 생성량이 감소되었다. 독성이 적고 투과성을 증가시키는 물질로서 toluene 대신 CTAB(Cetyltrimethylammoniumbromide)를 사용하였다. CTAB로 투과성을 증가시킨 세포를 k-carrageenan에 고정화하여 CSTR과 packed bed reactor를 이용하여 sorbitol 생산을 시도하였으며 CSTR보다도 (25일) packed bed reactor에서 (30일) 더 긴 시간 효소활성도가 유지되었다. Two-stage 연속공정에서는 희석비율이 (dilution rate, $h^{-1}$) 증가함에 따라서 sorbitol 생성률이 증가되었으며 희석비율 0.32 $h^{-1}$에서 첫번째와 두번째 반응조에서 각각 $15g/\ell-h,$ $22g/\ell-h의$ sorbitol 생성률을 얻었다. 0.32$h^{-1}$보다 높은 희석비율에서는 생성를이 감소되었다.

• Journal of Microbiology and Biotechnology
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• 제30권8호
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• pp.1227-1234
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• 2020

In this study, yeast cell immobilization was carried out in a packed bed reactor (PBR) to investigate the effects of the volumetric capacity of carriers as well as the different fermentation modes on fuel ethanol production. An optimal volumetric capacity of 10 g/l was found to obtain a high cell concentration. The productivity of immobilized cell fermentation was 16% higher than that of suspended-cell fermentation in batch and it reached a higher value of 4.28 g/l/h in repeated batches. Additionally, using this method, the ethanol yield (95.88%) was found to be higher than that of other tested methods due to low concentrations of residual sugars and free cells. Continuous ethanol production using four bioreactors showed a higher productivity (9.57 g/l/h) and yield (96.96%) with an ethanol concentration of 104.65 g/l obtained from 219.42 g/l of initial total sugar at a dilution rate of 0.092 h^-1. Furthermore, we reversed the substrate-feed flow directions in the in-series bioreactors to keep the cells at their highest activity and to extend the length of continuous fermentation. Our study demonstrates an effective method of ethanol production with a new immobilized approach, and that by switching the flow directions, traditional continuous fermentation can be greatly improved, which could have practical and broad implications in industrial applications.

• 대한수학회논문집
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• 제18권2호
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• pp.325-340
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• 2003

We introduce a fuzzy g-closure operator induced by a fuzzy topological space in view of the definition of Sostak [13]. We show that it is a fuzzy closure operator. Furthermore, it induces a fuzzy topology which is finer than a given fuzzy topology. We investigate some properties of fuzzy g-closure operators.

• Korean Journal of Mathematics
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• 제29권2호
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• pp.355-360
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• 2021

In this paper, we introduce the definition of sequentially g-connected components and sequentially locally g-connected by using sequentially g-closed sets. Moreover, we investigate some characterization of sequentially g-connected components and sequentially locally g-connected.

• 한국미생물·생명공학회지
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• 제16권3호
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• pp.205-212
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• 1988

Saccharomyces formosensis를 wood chip과 alginate gel에 고정화 실험을 한 결과, 모두 효모 고 정화도 매우 높으므로 고정화를 인한 Support로서 적절한 것으로 판단되었다. 관형발효기에 효모를 고 정화한 wood chip 및 alginate gel를 충전하여 연속발효 실험을 수행한 경우 0.446-0.485g EtOH/ g glucose로서 비슷하였으나, cell 수율은 alginate gel의 경우가 wood chip의 경우보다 낮아서 down stream의 처리시 유리하였다. 관형발효기의 에탄을 생산성은 wood chip을 이용할 경우 정상상태에서 에탄을 농도 68.3-54.9g/$\ell$ 범위에서 17.1-32.6g EtOH/$\ell$.hr를 나타내었고, alginate gel을 이용할 경우 정상상태에서 에탄올 농도 80.0-56.8g/$\ell$범위에서 에탄올 생산성은 20.0-32.0g EtOH/ hr를 얻었다. 본 실험의 에탄올 생산성은 다른 고정화법에 비하여 높았으며, 고정화 방법 중 alginate gel을 이용한 고정화법은 에탄을 생산을 위하여 효과적인 에탄을 생산 방법으로 사료되었다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제10권2호
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• pp.115-121
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• 2005

Using a general Saccharomyces cerevisiae as a model strain, continuous ethanol fermentation was carried out in a stirred tank bioreactor with a working volume of 1,500 mL. Three different gravity media containing glucose of 120, 200 and 280 g/L, respectively, supplemented with 5 g/L yeast extract and 3 g/L peptone, were fed into the fermentor at different dilution rates. Although complete steady states developed for low gravity medium containing 120 g/L glucose, quasi-steady states and oscillations of the fermented parameters, including residual glucose, ethanol and biomass were observed when high gravity medium containing 200 g/L glucose and very high gravity medium containing 280 g/L glucose were fed at the designated dilution rate of $0.027\;h^{-1}$. The observed quasi-steady states that incorporated these steady states, quasi-steady states and oscillations were proposed as these oscillations were of relatively short periods of time and their averages fluctuated up and down almost symmetrically. The continuous kinetic models that combined both the substrate and product inhibitions were developed and correlated for these observed quasi-steady states.