Oxidative and Reductive Routes of Glycerol and Glucose Fermentation by Escherichia coli Batch Cultures and Their Regulation by Oxidizing and Reducing Reagents at Different pHs |
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Authors: | Anna Poladyan Arev Avagyan Anait Vassilian Armen Trchounian |
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Institution: | 1. Department of Biophysics, Biology Faculty, Yerevan State University, 1 A. Manoukian Street, 0025, Yerevan, Armenia 2. Department of Microbiology, Plants and Microbes Biotechnology, Biology Faculty, Yerevan State University, 1 A. Manoukian Street, 0025, Yerevan, Armenia 3. Department of Ecology and Nature Protection, Biology Faculty, Yerevan State University, 1 A. Manoukian Street, 0025, Yerevan, Armenia
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Abstract: | Glycerol and glucose fermentation redox routes by Escherichia coli and their regulation by oxidizing and reducing reagents were investigated at different pHs. Cell growth was followed by decrease of pH and redox potential (E h ). During glycerol utilization at pH 7.5 ?pH, the difference between initial and end pH, was lower compared with glucose fermentation. After 8 h growth, during glycerol utilization E h dropped down to negative values (?150 mV) but during glucose fermentation it was positive (+50 mV). In case of glycerol H2 was evolved at the middle log phase while during glucose fermentation H2 was produced during early log phase. Furthermore, upon glycerol utilization, oxidizer potassium ferricyanide (1 mM) inhibited both cell growth and H2 formation. Reducing reagents dl-dithiothreitol (3 mM) and dithionite (1 mM) inhibited growth but stimulated H2 production. The findings point out the importance of reductive conditions for glycerol fermentation and H2 production by E. coli. |
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