Abstract
© The Author(s), under exclusive licence to Springer Nature B.V. 2025.Agri-food waste valorization for polyhydroxybutyrate (PHB) production is a sensible approach to decrease the cost of the production process of this biopolymer. The purpose of this project was to produce cost-effective PHB bioplastic from white grape pomace using a novel Bacillus strain. Twelve bacterial isolates were obtained from the soil of a municipal solid waste landfill; five isolates were PHB producers. Sudan Black-B staining and submerged fermentation technique were used to screen PHB-producing bacteria. Isolate MUN4 was the most potent PHB-accumulating bacterium that produced 2.5 ± 0.27 g/L of PHB and was recognized as Bacillus sp. MUN4 via 16S rRNA gene sequencing and phenotypic analysis. 16S rRNA nucleotide sequence of the bacterium was assigned accession number OR999895.1 in the NCBI database. The fermentation medium that contained 2% white grape pomace extract and ammonium sulfate exhibited the highest PHB production (4.63 ± 0.01 g/L). The XRD analysis indicated the PHB’s partial crystalline nature. The bioplastic structure of the PHB that was extracted was verified using FTIR, 1H NMR, 13C NMR, and GC-MS technology. The bioplastic was identified as PHB by considering hydroxyl, methylene, methine, methyl, and ester carbonyl groups, as well as three derivative products of butenoic acid at retention times of 14.96, 17.55, and 19.94 min. Bacillus sp. MUN4 may be an appropriate option for the environmentally benign and cost-effective industrial PHB production from white grape pomace.
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