Growth of Rhodospirillum rubrum on synthesis gas: conversion of CO to H2 and poly-beta-hydroxyalkanoate.
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(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% beta-hydroxybutyrate and 14% beta-hydroxyvalerate. Mass transfer of CO into the liquid phase was determined as the rate-limiting step in the fermentation.
Do
Young S
YS
Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA.
Smeenk
Jerod
J
Broer
Karl M
KM
Kisting
Clint J
CJ
Brown
Robert
R
Heindel
Theodore J
TJ
Bobik
Thomas A
TA
DiSpirito
Alan A
AA
D000445:Aldehyde Oxidoreductases / Q000378:metabolism; D001673:Biodegradation, Environmental; D019149:Bioreactors; D002248:Carbon Monoxide / Q000378:metabolism*; D005285:Fermentation; D006859:Hydrogen / Q000378:metabolism*; D006864:Hydrogenase / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism; D011108:Polymers / Q000378:metabolism*; D012247:Rhodospirillum rubrum / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism*
D009097:Multienzyme Complexes; D011108:Polymers; D002248:Carbon Monoxide; D006859:Hydrogen; D006864:Hydrogenase; D000445:Aldehyde Oxidoreductases; C019823:carbon monoxide dehydrogenase