Production of environmentally benign poly(hydroxybutyrate)/silver bionanocomposites reinforced with ZnO for active packaging of bread

The aim of the present work was to prepare poly(hydroxybutyrate) (PHB)-based active food packaging film with antimicrobial potential. For the sake of developing such film, PHB silver nanocomposites (PHB/Ag) were synthesized biologically using rice-washed water as substrate for Cupriavidus necator. These nanocomposites were further incorporated with varying concentrations of zinc oxide (ZnO) nanoparticles (1, 2, 3 and 4%), and thin films were obtained by solvent casting. Their morphological, thermal, mechanical, water barrier and antimicrobial properties were examined by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), tensile testing, water vapor permeability (WVP), and agar well diffusion assay, respectively. After the overall analysis, PHB/Ag-ZnO at 3% was designated as the optimized film. This film showed remarkable antimicrobial potential against tested food-borne pathogens i.e., Escherichia coli (E. coli, Gram-negative bacterium), Staphylococcus aureus (S. aureus, Gram-positive bacterium), and Aspergillus niger (A. niger, fungal strain). With this context, the above-selected film was used to check the shelf-life of a bread sample for 10 days of storage. The findings of the study evidenced that PHB/Ag-ZnO 3% extended the shelf-life of packaged bread up to 5–8 days. Thus, the present research work demonstrates that our prepared film has prolonged the shelf-life of packaged food and carries significant potential for active food packaging.

Graphical Abstract