Kefiran Production by Lactobacillus kefiranofaciens under the Culture Conditions Established by Mimicking the Existence and Activities of Yeast in Kefir Grains

Abstract

Kefiran production by Lactobacillus kefiranofaciens alone under the culture conditions established by mimicking the presence and activities of yeast cells in kefir grains was investigated. When the pH of the culture broth was controlled at pH 5.5 by adding a 4 N-NaOH solution during cultivation, cell growth and kefiran production were stimulated as compared with those in the cultivation without pH control. The addition of 5 g/l of yeast extract to the medium was essential for kefiran production. By sparging a mixed gas of N₂ and CO₂ at a volume ratio of 9:1 into the culture broth at 0.3 vvm throughout the cultivation, a slight increase in the amount (670 mg/l) of kefiran produced was observed as compared with that (650 mg/l) in the cultivation without aeration. When 10 g/l or 20 g/l of ethanol was added to the medium containing 50 g/l of lactose, the kefiran concentrations were about 930 mg/l or 840 mg/l at 8 days, respectively. The maximum concentration of kefiran obtained was about 1040 mg/l at 10 days, when 10 g/l of ethanol was added to the medium containing 75 g/l of lactose. These results showed that under the culture conditions established by mimicking the actions of yeast cells on L. kefiranofaciens in kefir grains the amount of kefiran produced was enhanced even when only the lactic acid bacterium was used.