Continuous Production of Lactic Acid from Molasses by Perfusion Culture of Lactococcus lactis Using a Stirred Ceramic Membrane Reactor

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A perfusion culture system was used for continuous production of lactic acid by retaining cells at a high density of Lactococcus lactis in a stirred ceramic membrane reactor(SCMR). After the cell concentration increased to 248 g/l, half of the culture broth volume was replaced with the fermentation medium. Subsequently, a substrate solution containing glucose(run 1)or molasses(run 2)was continuously supplied to the cells retained in the SCMR. Simultaneously, the culture supernatant was extracted using a ceramic filter with a pore size of 0.2 μm. The dilution rate was initially set at 0.4h^<-1> and gradually decreased to 0.2h^<-1> due to reduction in the permeability of the filter. The concentration of glucose in the substrate solution was adjusted to 60 g/l for the transition and the first period until 240h, 90 g/l for the second period from 240h to 440h, and 70 g/l for the third period from 440h to 643h. The average concentration of lactic acid in the filtrate reached 46 g/l in the first period, 43 g/l in the second period, and 33 g/l for the third period. The productivity obtained for the first period reached 15.8 g・l^<-1>・h^<-1> twice as much as that achieved in repeated batch fermentations. Based on the results obtained in run 1, the substrate solution containing 120 g/l of molasses was continuously supplied for 240h in run 2. The concentration and productivity of lactic acid reached 40 g/l and 10.6 g・l^<-1>・h^<-1> respectively, by continuously replenishing the culture medium at a dilution rete of 0.26h^<-1>. These results demonstrated that the filtration capacity of the SCMR was sufficient for a continuous and rapid replenishment of molasses solution from the dense cell culture and, therefore, the perfusion culture system is considered to provide a low-cost process for continuous production of lactic acid from cheap resources.
公益社団法人日本生物工学会の論文
1999-05-25

Continuous Production of Lactic Acid from Molasses by Perfusion Culture of Lactococcus lactis Using a Stirred Ceramic Membrane Reactor

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