Selection and cultivation of high-protein thermotolerant yeasts in molasses alcohol slop
1990
Siriphan Soponsathien
In a study of conditions of SCP production of Hansenula polymorpha DB18 grown on 0.1 % ammonium sulphate, 0.1 % potassium dihydrogenphosphate and 1 % glucose with an optimum initial pH of 6 at 45 deg. Celsius the results after 36 hrs were as follows: 7.99 gram dry cell weight per liter, with the condition of 1.8 vvm. aeration and 500 rpm agitation. The maximum growth yield after 36 hrs was 7.86 gram dry cell weight per liter. The sugar consumed by yeast from molasses alcohol slopBas a reducing sugar was 1.367 % and the protein content from dry cell weigth was 30.67 % as crude protein and 29.89 % as true protein. The BOD and COD of molasses alcohol slop decreasing respectively from 37,500 ppm to 25,750 ppm or 3.130 % and 185,431.23 ppm to 129,931.74 ppm or 29.93 %. In an aerobic continuous fermentation, SCP production was operated in a l L-continuous fermenter; 285 ml of working volume, control temperature at 45 deg C and maintained pH at 6. The experiment resulted in the culture of yeast being subjected to changing of dilution rates, as a dilution rate was at 0.19 hr-1, the appearance of the steady-state of the culture took place 12 hrs after the culture started and at this dilution rate we found the maximum SCP productivity occurred; 0.678 g/1/hr. Dry cell weight was 33.24 % as crude protein, 32.49 % as true protein in the SCP production of aerobic continuous fermentation but decreasing in reducing sugar consumption; 0.352 %, BOD and COD of molasses alcohol slop decreasing respectively from 39,166.66 ppm to 29,041.32 ppm or 25.85 % and 185,514 ppm to 144,673.61 ppm or 22.01 % which is less than in batch culture.
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