Biodegradation kinetics of dibenzoate plasticizers and their metabolites
The kinetics of the biodegradation of two commercial plasticizers, diethylene glycol dibenzoate (D(EG)DB) and dipropylene glycol dibenzoate (D(PG)DB), as well as two alternative plasticizers, 1,3-propanediol dibenzoate and 2,2-methyl-propyl-1,3-propanediol dibenzoate, were investigated in an aerated bioreactor. The experiments were conducted with resting cells of Rhodococcus rhodochrous, which had been grown with hexadecane as the substrate. The first step in the biodegradation was always the hydrolysis of an ester bond, releasing the corresponding monobenzoate and benzoic acid. Biodegradation of plasticizers and their associated metabolites were modeled using a Monod-type kinetic model. Significant differences between the biodegradation of commercial and alternative plasticizers were observed both in the biodegradation pathway and the biodegradation rates of monobenzoate metabolites. At a selected concentration of 0.4 g/L, the monobenzoates released from the biodegradation of 1,3-propanediol dibenzoate and 2,2-methyl-propyl-1,3-propanediol dibenzoate were degraded approximately 13 and 4 times more quickly, respectively, than the monobenzoate released from the biodegradation of D(PG)DB. The rapid biodegradation of monobenzoates released from microbial hydrolysis of alternative dibenzoate plasticizers was attributed to the lack of an ether bond in these compounds.
► Biodegradation kinetics of dibenzoate plasticizers was investigated. ► The effect of alkyl branches and ether function on biodegradation rate was studied. ► Dibenzoates were degraded to the monobenzoates as result of microbial hydrolysis. ► Removing the ether bond enhanced the biodegradation of the monobenzoates.
Journal: Biochemical Engineering Journal - Volume 70, 15 January 2013, Pages 35–45