Chloroform aerobic cometabolism by butane-growing Rhodococcus aetherovorans BCP1 in continuous-flow biofilm reactors

This work focuses on chloroform (CF) cometabolism by a butane-grown aerobic pure culture (Rhodococcus aetherovorans BCP1) in continuous-flow biofilm reactors. The goals were to obtain preliminary information on the feasibility of CF biodegradation by BCP1 in biofilm reactors and to evaluate the applicability of the pulsed injection of growth substrate and oxygen to biofilm reactors. The attached-cell tests were initially conducted in a 0.165 L bioreactor and, then, scaled-up to a 1.772 L bioreactor. Glass cylinders were utilized as biofilm carriers. The continuous supply of growth substrate (butane), which led to the attainment of the highest CF degradation rate (8.4 mgCF/day/m2 biofilm surface), was compared with 4 schedules of butane and oxygen pulsed feeding. The pulsed injection technique allowed the attainment of a ratio of CF mass degraded per unit mass of butane supplied equal to 0.16 mg CF / mg butane, a value 4.4 times higher than that obtained with the continuous substrate supply. A procedure based on the utilization of integral mass balances and of average concentrations along the bioreactors resulted in a satisfactory match between the predicted and the experimental CF degradation performances, and can therefore be utilized to provide a guideline for optimizing the substrate pulsed injection schedule.