Utilization of short chain monocarboxylic acids in an effluent of a petrochemical industry by Acinetobacter calcoaceticus.

The aqueous effluent generated by the Fischer--Tropsch process, containing a total of 13 g/L C(2)-C(5) monocarboxylic acids, was investigated as a potential substrate for the production of single-cell protein (SCP). A bacterial isolate, Acinetobacter calcoaceticus, could utilize all the acids in the effluent simultaneously in chemostat cultures, and no residual acids were detected in the culture below a dilution rate of 0.78 h(-1). The critical dilution rate was 1.04 h(-1). The maintenance energy requirement of the cells growing on the monocarboxylic acid mixture was considerably lower than that of cells growing on acetate as the sole carbon source. Enrichment of the effluent with ethanol to increase the biomass concentration was successful and still allowed the simultaneous and efficient utilization of all the carbon sources, but resulted in a decrease of the critical dilution rate by ca. 20%.