Growth of Rhodospirillum rubrum on synthesis gas: Conversion of CO to H sub(2) and poly-[beta]-hydroxyalkanoate

• Published in: Biotechnology and bioengineering Vol. 97; no. 2; pp. 279 - 286
• Main Authors: Do, Young S, Smeenk, Jerod, Broer, Karl M, Kisting, Clint J, Brown, Robert, Heindel, Theodore J, Bobik, Thomas A, DiSpirito, Alan A
• Format: Journal Article
• Language: English
• Published: 01.01.2007
• Subjects: Rhodospirillum rubrum
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.21226

To examine the potential use of synthesis gas as a carbon and energy source in fermentation processes, Rhodospirillum rubrum was cultured on synthesis gas generated from discarded seed corn. The growth rates, growth and poly- [beta]-hydroxyalkanoates (PHA) yields, and CO oxidation/H sub(2) evolution rates were evaluated in comparison to the rates observed with an artificial synthesis gas mixture. Depending on the gas conditioning system used, synthesis gas either stimulated or inhibited CO-oxidation rates compared to the observations with the artificial synthesis gas mixture. Inhibitory and stimulatory compounds in synthesis gas could be removed by the addition of activated charcoal, char-tar, or char-ash filters (char, tar, and ash are gasification residues). In batch fermentations, approximately 1.4 mol CO was oxidized per day per g cell protein with the production of 0.75 mol H sub(2) and 340 mg PHA per day per g cell protein. The PHA produced from R. rubrum grown on synthesis gas was composed of 86% [beta]-hydroxybutyrate and 14% [beta]-hydroxyvalerate. Mass transfer of CO into the liquid phase was determined as the rate-limiting step in the fermentation. Biotechnol. Bioeng. 2007; 97: 279-286.