Clint Kisting

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/H2 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… Show more

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/H2 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 H2 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 Show less

To examine the potential role of methanobactin (mb) as the extracellular component of a
copper acquisition system in Methylosinus trichosporium OB3b, the metal binding properties of mb were
examined. Spectral (UV-visible, fluorescence, and circular dichroism), kinetic, and thermodynamic data
suggested copper coordination changes at different Cu(II):mb ratios. Mb appeared to initially bind Cu(II)
as a homodimer with a comparatively high copper affinity at Cu(II):mb ratios below 0.2… Show more

To examine the potential role of methanobactin (mb) as the extracellular component of a
copper acquisition system in Methylosinus trichosporium OB3b, the metal binding properties of mb were
examined. Spectral (UV-visible, fluorescence, and circular dichroism), kinetic, and thermodynamic data
suggested copper coordination changes at different Cu(II):mb ratios. Mb appeared to initially bind Cu(II)
as a homodimer with a comparatively high copper affinity at Cu(II):mb ratios below 0.2, with a binding
constant (K) greater than that of EDTA (log K ) 18.8) and an approximate !G° of -47 kcal/mol. At
Cu(II):mb ratios between 0.2 and 0.45, the K dropped to (2.6 ( 0.46) × 108 with a !G° of -11.46
kcal/mol followed by another K of (1.40 ( 0.21) × 106 and a !G° of -8.38 kcal/mol at Cu(II):mb ratios
of 0.45-0.85. The kinetic and spectral changes also suggested Cu(II) was initially coordinated to the
4-thiocarbonyl-5-hydroxy imidazolate (THI) and possibly Tyr, followed by reduction to Cu(I), and then
coordination of Cu(I) to 4-hydroxy-5-thiocarbonyl imidazolate (HTI) resulting in the final coordination
of Cu(I) by THI and HTI. The rate constant (kobsI) of binding of Cu(II) to THI exceeded that of the
stopped flow apparatus that was used, i.e., >640 s-1, whereas the coordination of copper to HTI showed
a 6-8 ms lag time followed by a kobsII of 121 ( 9 s-1. Mb also solubilized and bound Cu(I) with a kobsI
to THI of >640 s-1, but with a slower rate constant to HTI (kobsII ) 8.27 ( 0.16 s-1), and appeared to
initially bind Cu(I) as a monomer. Show less