BIOPLASTIC FROM NATURE: MICROBIAL PRODUCTION OF THE BIOPLASTIC POLYHYDROXYBUTYRATE (PHB) FROM SOIL-DWELLING ISOLATED STRAINS AND THE FABRICATION OF BIODEGRADABLE THIN FILMS

Background: The global dependency on synthetic plastics has resulted in significant environmental pollution due to their persistence and poor biodegradability. As an alternative, biodegradable bioplastics such as polyhydroxybutyrate (PHB) offer promising eco-friendly solutions. PHB, a bacterial polyester, can be synthesized and extracted from microbial sources using renewable substrates, providing a sustainable option to replace petroleum-derived plastics. Objective: The objective of this study was to isolate PHB-producing bacteria from soil and characterize the extracted PHB both chemically and physically. Methods: Soil samples were collected from the IBGE garden, and a total of 15 bacterial isolates were cultured on nutrient agar. PHB-producing strains were identified using 0.05% Sudan Black B staining, and five isolates showed positive results. These PHB-positive strains were cultivated in PHB production media containing glucose as the carbon source. PHB extraction was performed using sodium hypochlorite and chloroform, and the yield was calculated based on cell dry weight (CDW). Chemical characterization was conducted using Fourier Transform Infrared Spectroscopy (FTIR), and the physical morphology of electrospun PHB nanofibers was analyzed using Scanning Electron Microscopy (SEM). Results: Among all isolates, 5AR yielded the highest PHB production with 0.53 g/L PHB and 1.04 g/L CDW, resulting in a 51.96% yield. Other isolates showed PHB yields as follows: 17AR (31.70%), 27AR (15.09%), 29AR (21.21%), and 45AR (11.76%). FTIR analysis revealed strong absorption peaks at 1723 cm⁻¹, 1720 cm⁻¹, 2946 cm⁻¹, and 1242 cm⁻¹, confirming PHB presence. SEM analysis showed successful fabrication of nanofibers from extracted PHB. Conclusion: This study confirms the potential of soil bacteria in producing PHB and supports their use in bioplastic production. The extracted PHB showed comparable properties to standard PHB, indicating feasibility for eco-friendly applications.