In order to obtain the basic informations on the production of single cell protein from ethanol, 145 yeast strains utilizing ethanol as a sole carbon source were isolated from 32 soil samples in Korea.
A yeast strain showing the highest cell yield among the isolated strains was selected and identified.
The optimum culture condition, utilization of other carbon sources and the cultural characteristics for the selected yeast, and the chemical analysis of the yeast cell composition, and utilization of ethanol by the selected yeast were investigated. All the culture was carried out in the shaking flasks.
The results obtained were as follows:
1. The selected yeast strain was identified as Debaryomyces nicotianae-SNU 72.
2. The optimum composition of the medium for the selected yeast is : Ethanol 40 ㎖, Urea 0.5 g, Potassium phosphate (dibasic) 0.5 g, Ammoium phosphate (monobasic) 0.15 g, Magnesium sulfate 0.05 g, Calcium chloride 0.018. Yeast extract 0. 005 g, Tap water 1000 ㎖.
3. The optimum pH was 5.0-5.5, the optimum temperature 30-33℃ and the aerobic state was unimportant.
4. Utilization of methanol, n-propanol, iso-proparol, n-butanol, iso-butanol, tert-amyl alcohol and acetic acid by the selected yeast was very weak. So substitution of the subtrate was thought to be impossible.
5. Studies on the propagation of the yeast cells showed that the lag phase of the yeast cells lasted 16 hours, and the logarithmic growth phase extended 16 to 28 hours. The specific growth rate was about 0.19 hr^(-1) and the doubling time was 3. 6 hours during. the logarithmic growth phase.
6. As the result of the chemical analysis of the dry yeast cells, the content rate of the crude protein was 55.19 %, the content of others was similar to the average content of the yeast component.
7. After 34 hours cultivation, under the optimum culture condition investigated, the dry cell yield against the amount of the added ethanol was 53.4 % (W/V%), the dry cell yield against the amount of the utilized ethanol was 73.6 % (W/V%), the evaporation rate of ethanol was about 19.1 %.
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