Biodegradation of polystyrene (PS)-poly(lactic acid) (PLA) nanocomposites using Pseudomonas aeruginosa

Poly(lactic acid) (PLA) was synthesized using condensation polymerization of L-lactic acid using a controlled ultrasonic cavitation technique. Polystyrene (PS) was used to prepare the PS:PLA and PS:PLA:organically modified montmorillonite (OMMT) composites. PS was dissolved in benzene (10:90) and kept overnight for dissolution. Meanwhile, surface modification of montmorillonite was done using a column chromatography technique and referred to as OMMT. The d-spacing was found to be 22 after modification due to sufficient column length and diameter with good retention time during ion exchange. PLA and OMMT were kept in hot air oven at 100 oC for 30 min to remove the moisture. The mixtures of 10%, 15%, 20%, 25%, and 30% of PS:PLA:OMMT were subjected to ultrasonic irradiation (50 Hz) for homogenization and to form a biodegradable polymer nanocomposite sheet (5 x 5 cm(2)). The amount of OMMT loading was from 0.5-5 mass%. These composites were subjected to degradation in minimal medium using Pseudomonas aeruginosa bacteria at controlled conditions, and the polymer is a major source of carbon. The degradation was confirmed using scanning electron microscopy, extracellular protein content change, biomass production, and % degradation with respect to time (up to 28 days) after incubation.