Biodegradation of eugenol-loaded polyhydroxybutyrate films in different soil types

Polyhydroxybutyrate (PHB) has been considered as packaging material in many recent applications due to its high crystallinity, biodegradability, low interaction with food matrix and favorable barrier and mechanical properties. Although the incorporation of antimicrobial agents in its structure may control surface microbial contamination of foods, they can affect the film properties. In this study, eugenol-loaded PHB films were prepared using a solvent casting technique, which were subsequently exposed to a biodegradation study for 60 days in agricultural, sandy and landfill soil. Thermal analysis, X-ray diffraction, tensile tests and disk diffusion assay were performed to evaluate the physicochemical and microbiological changes. A concentration-dependent antimicrobial effect was observed. PHB films buried in agricultural soil presented a higher rate of biodegradation, which may be particularly associated with the high fungi load and higher soil-phosphorus availability. The soil acidity, phosphorus availability, moisture level and polymer crystallinity were key factors in explaining the differences in microbial growth and biodegradation rates. The addition of eugenol in PHB films enhanced the crystallinity of the polymer and reduced their mechanical properties. Overall, the incorporation of eugenol in PHB films was a successful approach to develop new active packaging for the food industry.