ISSN:
0006-3592
Keywords:
Chemistry
;
Biochemistry and Biotechnology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Energetic and reaction-rate interactions between hydrogenic (hydrogen-producing) and hydrogenotrophic (hydrogen-consuming) bacteria were investigated in five perturbation experiments performed on steady-state, mixed-culture methanogenic CSTRs receiving ethanol, propionate, or both hydrogenic substrates. When a large quantity of propionate was suddenly added to a propionatefed CSTR, PH2 increased to 10-4 atm and propionate oxidation remained energetically favorable. When ethanol was added to a CSTR receiving ethanol, PH2 rose to 6.3 × 10-3 atm within 5 h. In both perturbations, PH2 remained at levels such that oxidation of the hydrogenic substrate remained energetically favorable throughout the transient. Sudden increase in ethanol concentration in the ethanol- and propionate-fed CSTR resulted in an increase in PH2 such that propionate oxidation became energetically unfavorable and was blocked. Propionate utilization resumed when the added ethanol was depleted and PH2 returned to its previous steady-state levels. Ethanol perturbation of ethanol- and propionate-fed CSTRs led to the formation of reduced products, including n-propanol and four-through seven-carbon n-carboxylic acids, when PH2 was elevated; these products disappeared after PH2 returned to previous, steady-state levels. The transformations were consistent with reaction energetics. Reduced product formation may have been a sink for reducing equivalents, as an alternative to oxidation for propionate utilization, as indicated by an electron equivalents balance over the time course of experiments.
Additional Material:
13 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bit.260340106
