본 연구에서는 식품부산물을 원료로 사용하여 회분식 발효를 통한 Propionibacterium acidipropionici의 유기산 생산성을 검토하고 세포재순환식 연속발효를 통해 유기산의 대량생산을 위한 기초자료를 마련하고자 하였다. CSL의 함유량에 따른 회분식 발효를 실시하여 균주의 생산성이 최대가 되는 발효조건을 구하여 연속 발효공정에 적용하였다. 희석률을 $0.1{sim}0.2;hr^{-1}$로 변화시키며 세포재순환식 연속발효를 실시한 결과 $0.2;hr^{-1}$에서 최대 세포량은 150 g drycell/L으로 회분식 발효에 비해 21배 증가하였으며, 유기산의 최대 생산성은 3.32 g total acids/L/h로서 13배가 향상된 것으로 나타났다. 따라서 이 발효공정을 scale-up한다면 유기산뿐만 아니라 바이오매스 자원으로서 세포량의 대량생산도 가능할 것으로 판단된다.
Fermentation studies were conducted in batch and continuous flow cell-recycle reactors with food by-products as substrates. The genus Propionibacterium acidipropionici ATCC 4965 was utilized in the production of organic acids. Good performance was achieved in the batch fermentation using hydrol as a carbon source and corn steep liquor (CSL) as nitrogen and vitamin sources. Product yields and productivity based on maximum values were 0.80 g total acids/g glucose and 0.26 g total acids/L/h, respectively, when $3\%$, (w/v) of hydrol and $2.5\%$, (w/v) of CSL were utilized. Continuous fermentation with cell-recycling system using the optimum amounts of substrates resulted in dramatic increase in cell concentration (X) and maximum productivity (P). Compared to the batch fermentation, X and P were increased by as much as 21 and 13 times, respectively, at the dilution ratio of $0.2;hr^{-1}$, indicating that cell recycling fermentation of food by-products provides valuable means for the mass production of organic acids as well as utilizing cell mass as good nutrient resources.
