Modeling the Kinetics of Contaminant Biodegradation by a Mixed Microbial Consortium Based on Carbon Mass Balance

Abstract

The fate of contaminant carbon was monitored during aerobic biodegradation in the presence of a mixed indigenous microbial consortium in order to calibrate a microbial-growth-based biokinetic model. The methodology simultaneously monitored mineralization, substrate depletion and microbial population evolution in biomass extract spiked with14C-labeled hexadecane. Hexadecane depletion and hexadecane-degrader population were monitored using sacrificed microcosms by centrifuging the extract so that the supernatant and the residue contained residual hexadecane and microbial population, respectively. This methodology allowed verification of the carbon mass balance (average14C-carbon recovery of 90.33 ± 1.62% for biotic microcosms) and calibration of a biokinetic model. Four biokinetic parameters and three yield coefficients were identified (Haldane kinetic parameters:μS = 1.3639 d-1, Ks = 0.4295 mg-C, KI = 6.6457 mg-C; decay kinetic parameter:μd = 1.3.102 d-1; substrate/biomass, carbon dioxide/ biomass during growth and carbon dioxide/biomass during decay yield coefficients: Ys = 1.5948 mg-C/mg-C, YP g = 0.4554 mg-C/mg-C, YP d = 1.3263 mg-C/mg-C) and compared with the literature data. The methodology can facilitate the identification of biodegradation models by decoupling the intrinsic ability of microorganisms to degrade contaminant from restrictions imposed by limiting conditions.