Enhancement of biomass and fermentation activity of surplus brewers' yeast in a fed-batch process |
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Authors: | Biserka Strel Slobodan Grba Vladimir Maric |
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Institution: | (1) Ministry of Science and Technology, Industrial Property office of Republic of Slovenia, Slovenska 50, 61000, Ljubljana, Slovenia;(2) Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, 41000 Zagreb, Croatia |
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Abstract: | The growth of surplus brewers' yeast in a fed-batch process was studied with the aim of increasing the fermentation activity of the yeast cells and of optimizing the growth conditions: 20 h cultivation at 30° C and pH 5.0–5.5 using beet molasses as substrate, with a regulated feeding rate, showed satisfactory results. Under the chosen conditions, the final amount of biomass increased more than fivefold, achieving a specific growth rate of 0.1 h–1 and substrate yield coefficient of 0.54 g·g–1. The increase in fermentation activity of yeast cells during cultivation correlated very well with the concentration of reduced glutathione, which increased from 1.2 to 2.7 mg·g–1 (dry matter). At the same time the fermentation activity increased fivefold, which related to the nitrogen content of the yeast cells. Ethanol formation throughout the cultivation did not exceed 0.5 g·l–1.
Correspondence to: B. Strel |
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