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.
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.
