Enhancing the biodegradation rate of poly(lactic acid) films and PLA bio-nanocomposites in simulated composting through bioaugmentation

Biodegradable polymers provide an opportunity to divert plastic waste from landfills, with composting as an alternative disposal route. However, some biodegradable polymers, such as poly (lactic acid) (PLA), do not biodegrade as fast as other organic wastes during composting, affecting their general acceptance in industrial composting facilities. Bioaugmentation, the addition of specific microbial strains, is a promising technique to accelerate the biodegradation of compostable plastics, so that they biodegrade in comparable time frames with other organic materials. In this study, we evaluated the effect of bioaugmentation on the biodegradation of PLA and PLA bio-nanocomposites (BNCs) in simulated corn posting conditions. PIA, PLA with 5% organo-modified montmorillonite (PLA-OMMT5), and PIA with 0.4% surfactant (PLA-QACO.4) films were produced and fully characterized. PLA-degrading bacteria were isolated through an enrichment technique with PLA as the sole carbon source at 58 degrees C. Isolates were identified as Geobacillus using 16 S rRNA gene sequencing and the NCBI database, and further used to study the effect of bioaugmentation on the biodegradation rate of PLA and BNCs in solid environments. The biotic and abiotic degradation was assessed in compost, inoculated vermiculite, and uninoculated vermiculite at 58 degrees C by analysis of evolved CO2 using an in-house built direct measurement respirometer. Size exclusion chromatography was also used to measure and to monitor the change in molecular weight of the film samples retrieved every week during the biodegradation test. The microbial attachment on the surface of PLA of the isolated microbial strain and other microorganisms present in the compost was evaluated by a biofilm forming assay in wells incubated at 58 degrees C. Bioaugmentation with Geobacillus increased the evolution of CO2 and accelerated the biodegradation phase of PLA and BNCs when tested in compost and inoculated vermiculite with compost mixed culture. Bioaugmentation could commercially be used to accelerate the biodegradation of PLA in compost environments. (C) 2018 Elsevier Ltd. All rights reserved.