Development of Strategy for Fermentative Production Based on Symbiosis of Microorganisms

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In a batch mixed culture of L.kefiranofaciens and S.cerevisiae, which could assimilate lactic acid, cell growth and kefiran production rates of L.kefiranofaciens significantly increased, compared with those in pure cultures. The kefiran production rate was 36 mg ・l^<-1> ・h^<-1> in the mixed culture under the anaerobic condition, which was greater than that in the pure culture (24 mg ・l^<-1> ・h^<-1>). Kefiran production was further enhanced by an addition of fresh medium in the fed-batch mixed culture. In the fed-batch mixed culture, a final kefiran concentration of 5.41 g ・l^<-1> was achieved at 87 h. Simulation study considered the reduction of lactic acid in pure culture suggested that coculture of L.kefiranofaciens and S.cerevisiae not only reduced the lactic acid concentration by consumption but also stimulated cell growth and kefiran production of L.kefiranofaciens. R eduction of hydrogen peroxide did not concern in stimulation of kefiran production of L.kefiranofaciens in mixed culture. It was also found that the addition of spent medium of yeast was not the main effect for increasing in capsular kefiran in the mixed culture. And in a non-contact mixed culture, there was also no increase in capsular kefiran production of L.kefiranofaciens as much as ii was found in mixed culture. Increase in capsular kefiran in the mixed culture with inactivated S.cerevisiae agreed well to that in anaerobic and aerobic mixed culture. In the mixed culture with inactivated S.cerevisiae by glass beads disruption, the increase of capsular kefiran was less than that in mixed culture with inactivated S.cerevisiae by heat treatment. From these fermentation results, it was concluded that the physical contact interaction with S.cerevisiae enhanced the capsular kefiran production of L.kefiranofaciens in mixed culture.