Bioenergetic analysis of the growth of the binary mixed culture (Pseudomonas aeruginosa and Pseudomonas fluorescence) on phenol chemostat culture was carried out. The data were checked for consistency using carbon and available electron balances. When more than the minimum number of variables are measured, and measurement errors are taken into account, the results of parameter estimation depend on which of the measured variables are chosen for this purpose. Similar parameter estimates were obtained using Pirt’s model based on the Monod equation approach and a modified model based on substrate consumption  being rate limiting. Coupled with the covariate adjustment estimation technique, the best estimates were the maximum likelihood estimates (MLE) based on when all the measured data were used. For the aerobic growth of the mixed culture on phenol,   phenol, ηmax = 0.396.0  and me=-0. 020.0h-1. From the 95% confidence intervals, a maximum of about 38 – 41.3% of the energy contained in phenol is incorporated into the mixed culture biomass. The balance (58.7 – 62%) is evolved as heat with little or no energy needed for the maintenance of organisms.

Key words: Binary mixed culture, biomass energetic yield, chemostat culture, energetic analysis, maintenance coefficient, Pirt’s model.