Polyhydroxybutyrate (PHB) has gained attention as an excellent packaging material due to its high crystallinity, biodegradability, low interaction with food matrices, and favorable mechanical properties. This study explores the development of PHB films incorporated with potassium sorbate (KS) and gallic acid (GA) via solvent casting, followed by a 30-day biodegradation test in soil. The films are analyzed for physicochemical and microbiological properties using X-ray diffraction, tensile testing, and disk diffusion assays. The soil-buried PHB films demonstrate accelerated biodegradation, likely driven by increased microbial and fungal activity, as well as moisture absorption. Incorporating KS and GA significantly enhances the antimicrobial efficacy of the films against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, with greater inhibition observed against S. aureus. This difference may stem from the additional lipopolysaccharide membrane in E. coli. Field emission scanning electron microscopy (FESEM) of the films, both pre- and post-biodegradation, provides further insights into their structural changes. These findings underscore the potential of PHB antimicrobial films in advancing sustainable food packaging applications.

Escalating usage of non-degradable plastics is raising significant concern. The search for bio-based degradable alternatives commenced far back, and the burgeoning progress in the development of bioplastics is featured as a critical solution to ongoing plastic pollution. Bioplastics are becoming a promising substitute for petroleum-based plastics, depending on the production source and post-use disposal management. Among all the promising materials, microbially produced polyester and polyhydroxybutyrate (PHB) belong to the polyhydroxyalkanoate (PHA) family and are biocompatible and non-toxic. PHB has remarkable thermal and mechanical properties, making it a potential replacement for ubiquitous plastics. In this study, PHB-producing bacteria were isolated from mangrove soil and checked for PHB accumulation using preliminary and confirmatory staining. Out of a total 25 isolates, 13 were found positive for PHB accumulation. Dairy wastewater was used as a cultivation medium for PHB production; the potential PHB-producing strain was selected for morphological and biochemical characterization up to the genus level and was found to be Bacillus sp (3.6 +/- 0.15g/L). Extracted PHB was characterized using FTIR, XRD, and TGA; in FTIR, the characteristic peak was recorded at 1724 cm-1, and XRD showed the crystallinity of PHB. outcome of the present study shows that dairy wastewater is an indispensable medium for PHB production in an eco-friendly way.

This study targets explicitly finding an alternative to petroleum-based plastic films that burden the environment, which is a high priority. Hence, polymeric films were prepared with carboxymethyl cellulose (CMC) (4%), pectin (2%), and polyhydroxybutyrate (PHB) (0.5%) with different concentrations of thymol (0.3%, 0.9%, 1.8%, 3%, and 5%) and glycerol as a plasticizer by solution casting technique. The prepared films were tested for mechanical, optical, antimicrobial, and antioxidant properties. Film F5 (CMC + P + PHB + 0.9%thymol) showed an excellent tensile strength of 15 MPa, Young's modulus of 395 MPa, antioxidant activity (AA) (92%), rapid soil biodegradation (21 days), and strong antimicrobial activity against bacterial and fungal cultures such as Klebsiella pneumoniae, Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Aspergillus flavus. The thymol content increase in films F6 (1.8%), F7 (3%), and F8 (5%) displayed a decrease in mechanical properties due to thymol's hydrophobicity. For shelf life studies on tomatoes, F2, a film without thymol (poor antimicrobial and antioxidant activities), F5 (film with superior mechanical, optical, antimicrobial, and antioxidant properties), and F7 (film with low mechanical properties) were selected. Film F5 coatings on tomato fruit enhanced the shelf life of up to 15 days by preventing weight loss, preserving firmness, and delaying changes in biochemical constituents like lycopene, phenols, and AA. Based on the mechanical, optical, antimicrobial, antioxidant, and shelf life results, the film F5 is suitable for active food packaging and preservation.