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Optimum alcohol concentration for chain elongation in mixed‐culture fermentation of cellulosic substrate
Author(s) -
Lonkar Sagar,
Fu Zhihong,
Holtzapple Mark
Publication year - 2016
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.26024
Subject(s) - fermentation , ethanol , chemistry , caprylic acid , food science , acetic acid , valeric acid , elongation , butyric acid , biochemistry , alcohol , butyrate , fatty acid , materials science , metallurgy , ultimate tensile strength
Medium‐chain fatty acids (MCFA, e.g., caproic, heptanoic, caprylic acid) are more valuable than short‐chain fatty acids (SCFA, e.g., acetic, propionic, butyric, valeric acid). SCFAs are major products in methane‐inhibited mixed‐culture anaerobic fermentation. By feeding ethanol to the fermentor, MCFA formation is enhanced through chain elongation. Microorganisms such as Clostridium kluyveri elongate short‐chain acids by combining them with alcohol. Very low ethanol concentration reduces chain elongation rates, whereas very high ethanol concentrations inhibit microorganisms. To maximize MCFA production, different ethanol concentrations were investigated in the mixed‐culture fermentation of office paper and chicken manure. At 10 g/L ethanol concentration, 10 g/L MCFA was formed. High ethanol concentrations (above 40 g/L) inhibit microorganisms resulting in no chain elongation. For chain elongation, propanol was found to be more inhibitory than ethanol. The data suggest that MCFA production will increase by continuously extracting MCFA and maintaining 5–10 g/L ethanol concentration by periodic addition. Biotechnol. Bioeng. 2016;113: 2597–2604. © 2016 Wiley Periodicals, Inc.