UBC Theses and Dissertations
Yeast cultivation on natural starches Helbig, Nelia Bendana
This research project is concerned with the use of an amylolytic yeast, Endomycopsis sp., for simultaneous production of yeast protein and crude amylase preparations from natural starch materials. The Endomycopsis yeasts were cultivated alone and in combination with other yeasts which are unable to attack starch directly. The propagations were carried out in the presence of urea and phosphate, under aerobic conditions, with vigorous agitation, at pH 5.0 and 28°C. At daily intervals, the cultures were analyzed for protein yield, cell density, and amylase activity. The cell crop harvested after propagation of Endomycops is yeasts on 6.0% potato media contained 19% protein and the culture filtrate obtained after biomass separation had an activity of 1.5 units. Variations in activity and protein content were observed, depending on the starch substrate used, the concentration of urea added, and apparently, the amount of oxygen supplied. Mixed preparations using Candida utilis as ancillary yeast, gave higher protein yields and amylase activities compared to single propagations of Endomycopsis sp. and mixed propagations with Saccharomyces cerevisiae. Purple yam and cassava tubers were examined for protein enrichment and amylase production. It was observed that the protein content of the cell crops obtained from these substrates could be increased about ten-fold but that the amylase activities of the culture filtrates were very low .
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