KINETIC CHARACTERIZATION OF MASS-TRANSFER LIMITED BIODEGRADATION OF ALOW WATER-SOLUBLE GAS IN BATCH EXPERIMENTS - NECESSITY FOR MULTIRESPONSE FITTING

A method was developed to characterize the kinetics of biodegradation of low water soluble gaseous compounds in batch experiments. The degra dation of ethene by resting Mycobacterium E3 cells was used as a model system. The batch degradation data were recorded as the progress curv e (i.e., the time course of the ethene concentration in the headspace of the batch vessel). The recorded progress curves, however, suffered gas:liquid mass transfer limitation. A new multiresponse fitting metho d had to be developed to allow unequivocal identification of both the affinity coefficient, K-aff, and the gas:liquid mass transfer coeffici ent, Kja, in the batch vessel from the mass transfer limited data. Sim ulation showed that the K-aff estimate obtained is influenced by the d imensionless (volumetric basis) ethene gas:liquid partitioning coeffic ient (H). In the fitting procedure, Monod, Teissier, and Blackman biok inetics were evaluated for characterization of the ethene biodegradati on process. The fits obtained reflected the superiority of the Blackma n biokinetic function. Overall, it appears that resting Mycobacterium E3 cells metabolizing ethene at 24 degrees/C have, using Blackman biok inetics, a maximum specific degradation rate, V-max, of 10.2 nmol C2H4 mg(-1) CDW min(-1), and an affinity coefficient, K-aff.gr expressed i n equilibrium gas concentration units, of 61.9 ppm, when H is assumed equal to 8.309. (C) 1997 John Wiley & Sons, Inc.