Optimization and characterization of polyhydroxybutyrate produced by Halomonas meridiana using orange peel waste

The production of bioplastics from marine microorganisms is significantly relevant in the field of biotechnological applications for sustainable ecological management. Nevertheless, the expense associated with PHB production is substantial and regarded as the primary obstacle to its industrialization. In this study, orange peel waste served as a carbon source to enhance PHB production efficiency. Among the 15 strains evaluated, MH 96 was selected for PHB production due to its high salt tolerance and efficient utilization of orange peel as a substrate. The highest producing PHB strain MH96 was genetically identified using 16S rRNA sequencing as Halomonas meridiana and submitted in the GenBank under accession numbers PP826284. The optimal fermentation conditions were evaluated through single-factor optimization. Upon completion of the response surface optimization, the Plackett-Burman and Box-Behnken design experiments were conducted utilizing the outcomes of the single-factor optimization. The final parameters were the inoculum size of 1.74, (NH₄)₂HPO₄ concentration of 1.0 and pH 6.37, and PHB yield of 5.94 g/L. The characterization of the extracted biopolymer by NMR, FTIR, XRD, and thermal properties was used to examine the properties of the extracted PHB, and gas chromatography-mass spectrometry (GC-MS) proves the presence of 2-butenoic acid, 1-methyl ethyl ester, tetradecane, hexadecanoic acid, methyl ester, and docosanoic acid, 8,9,13-trihydroxy-. Methyl ester, which confirmed the structure of the polymer as PHB.