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Published on: October 24, 2016
Effects of propionic acid and pH on ethanol fermentation by Saccharomyces cerevisiae in cassava mash
Cheng-Ming Zhang1, Li Jiang, Zhong-Gui Mao
1The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China.
Abstract:
The effects of propionic acid on ethanol and glycerol production by Saccharomyces cerevisiae in cassava mash were examined along with the influence of pH (4.0, 5.0, and 6.0) and of dissolved solids content (22%, 25%, and 27%). Inhibition by propionic acid increased as solids content increased and medium pH declined. Complete inhibition of ethanol fermentation was observed in mashes at pH 4.0 (60 mM propionic acid for 22% solids and 45 mM for 25% and 27%). Glycerol production linearly decreased with increased undissociated propionic acid concentration in all mashes at all pH levels, which partly contributed to increased final ethanol production when propionic acid concentration in mashes was low (≤ 30 mM).
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