Polyhydroxyl Butyrate Production Using Biogas Slurry

Polyhydroxybutyrate (PHB) is a type of polyhydroxyalkanoate (PHA), a biopolymer produced by various bacterial species as a means of carbon and energy storage. It has garnered significant interest in recent years due to its biodegradability and potential to replace conventional petrochemical-based plastics, which pose severe environmental challenges. Polyhydroxybutyrate (PHB) is a type of polyhydroxyalkanoate (PHA), a biopolymer produced by various bacterial species as a means of carbon and energy storage. It has garnered significant interest in recent years due to its biodegradability and potential to replace conventional petrochemical-based plastics, which pose severe environmental challenges. This Project investigates the isolation, screening, and characterization of polyhydroxybutyrate (PHB)-producing bacteria from biogas slurry samples collected at Chukwuemeka Odumegwu Ojukwu University (COOU), Uli. Samples were collected in sterile containers, refrigerated at 4°C, and processed in the laboratory. Serial dilution and streak plate methods were employed for bacterial isolation, followed by primary and secondary screening for PHB production using Sudan Black B and Nile Red staining methods. The positive PHB-producing strains were characterized through a series of biochemical tests including catalase, indole, motility, methyl red-Voges Proskauer, citrate, urease, gelatin liquefaction, nitrate reduction, hydrogen sulfide production, sugar fermentation, and oxidase tests.The selected strains were cultivated in HM-2 medium, and PHB was extracted using chloroform and purified through methanol precipitation. The extracted PHB was characterized using Fourier Transform Infrared (FTIR) spectroscopy, UV-visible spectrophotometry, and Thin Layer Chromatography (TLC). The study also quantified PHB production by measuring cell dry weight and converting PHB to crotonic acid, which was quantified spectrophotometrically at 235 nm. Results indicated that strains PHB 2, PHB 5, and a consortium of both demonstrated significant PHB production. The consortium exhibited enhanced growth (OD600 nm = 1.245), dry biomass (5.00 g/L), and PHB content (3.00 g/L) compared to individual strains. PHB yield as a percentage of dry biomass was highest in PHB 5 (50.97%), followed by the consortium (48.72%), highlighting the efficiency of combined metabolic pathways in PHB synthesis. This study underscores the potential of biogas slurry as a resource for isolating efficient PHB-producing bacteria, which could be pivotal in bioplastic production.