Influence of process parameters on growth of Clostridium ljungdahlii and Clostridium autoethanogenum on synthesis gas |
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Authors: | Jacqueline L Cotter Mari S Chinn Amy M Grunden |
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Institution: | 1. Department of Biological and Agricultural Engineering, North Carolina State University, Weaver Labs, Campus Box 7625, Raleigh, NC 27695-7625, United States;2. Department of Biological and Agricultural Engineering, North Carolina State University, 277 Weaver Labs, Campus Box 7625, Raleigh, NC 27695-7625, United States;3. Department of Microbiology, North Carolina State University, 4550A Gardner Hall, Campus Box 7615, Raleigh, NC 27695-7615, United States |
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Abstract: | Effects of initial medium pH and gas flow rate on Clostridium ljungdahlii and Clostridium autoethanogenum in liquid batch, continuous gas fermentations were investigated. Synthesis gas components were supplied at varying flow rates (5, 7.5 and 10 mL/min) for C. ljungdahlii (pH 6.8 and 5.5) and C. autoethanogenum (pH 6.0). Growth on synthesis gas was slower than growth on sugars. For C. ljungdahlii, higher cell densities were achieved at pH 6.8 (579 mg/L) compared to pH 5.5 (378 mg/L). The ethanol concentration at pH 6.8 was also 110% greater than that at pH 5.5. The interaction of flow rate and pH was statistically significant with the greatest acetate production in the 10 mL/min, pH 6.8 treatment. The ethanol to acetate ratios were smaller at lower pH levels and higher flow rates. In C. autoethanogenum fermentations, higher flow rates resulted in greater end product formation with no significant effect on product ratios. |
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