Growth of Rhodospirillum rubrum on synthesis gas: Conversion of CO to H 2 and poly‐β‐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: 01.06.2007
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.21226

Abstract 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‐β‐hydroxyalkanoates (PHA) yields, and CO oxidation/H 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 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% β‐hydroxybutyrate and 14% β‐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. © 2006 Wiley Periodicals, Inc.