Phenotypic Screening and VITEK®2-Based Identification of Polyhydroxybutyrate (PHB)- Producing Bacteria isolated from Agro-Industrial Waste Sites in Iraq

Abstract The growing accumulation of non-biodegradable plastics has become a global environmental crisis, prompting the search for sustainable and biodegradable alternatives such as bioplastics. This study aimed to isolate and characterize novel bacteria capable of producing PHAs, a type of biodegradable bioplastic, from agro-industrial environment. In this study, forty environmental samples including soil, wastewater, and sludge were collected from the vicinity of the Union factory for Sugar and Oil production in province of Babylon in Iraq. Bacterial isolation was conducted using cellulose-enriched mineral salt medium (MSM) where 15 pure isolates were obtained. For preliminary qualitative detection of PHB accumulation, Sudan Black B staining was done which showed positivity with six isolates that had dark blue to black colonies suggesting they were PHB positive. Examination under microscope confirmed that these constituents have prominently visible granules filled with PHB inside the cell structure. The strains which produce PHB were identified using VITEK®2 compact system and it indicated the following species: Enterobacter cloacae, Escherichia coli, Kocuria kristinae. The industrial waste settings can serve as reservoirs for microorganisms that produce PHA, which can support the development of sustainable bioplastics and encourage the circular economy by valuing trash. This study emphasizes the significance of using low-cost substrates and native bacterial strains for the production of bioplastics in a scalable and ecologically responsible manner.