Kinetics study of biodegradation of polyethylene terephthalate by E. coli and S. aureus with enhancers lactic acid and glycolic acid

Hydrolase enzymes secreted from microorganisms as metabolic byproducts can hydrolyze polyethylene terephthalate (PET) to produce terephthalic acid and ethylene glycol. Two culture media of E. coli (BL21), S. aureus (UAMS-1) including a mixed culture medium of both were used with lactic acid and glycolic acid (LA/GA) as enhancers for the present investigation of (PET) biodegradation. The rate of degradation showed a linear relationship for the first 60 days and the values of specific surface degradation rate calculated from the slopes of the regression line of showed an average of 92% matching with experimental and theoretical values, satisfying the proposed mathematical model of kinetics. Optical Density, UV-visible, Mass, IR and DTA analytical techniques were performed to study the mode of biodegradation and it was found that the crystallinity of the PET samples after biodegradation increased indicating the amorphous phase attacking of PET sample firstly and after 60 days, the microbes attacked both the crystal and amorphous phases with a little amount of micro-plastic formation. Chemical hydrolysis proceeded (up-to 20%) in presence of enhancer as the mixture of LA/GA in slightly basic medium (pH=7.30). Both chemical and biological attacking of PET can be a new dimension of controlling PET plastic pollution.