Sustainable Poly(3-hydroxybutyrate) Bioplastic Production by Extremely Halophilic Haloarcula sp. PLQ Isolated from Qatari Extreme Environments

With the increase in Qatar’s population, the generation of plastic waste has grown, resulting in high levels of environmental pollution. Polyhydroxyalkanoates are sustainable bio-alternatives to petrochemical plastics. Despite their market potential, the industrial implementation of PHAs is still limited. This study aimed to develop sustainable processes for PHA accumulation by screening and isolating novel haloarchaeal strains from Qatari extreme environments with the ability to convert carbon sources to PHAs. In total, 24 positive haloarchaeal members, belonging to Natrinema, Haloarcula, and Halostagnicola genera, were identified for the first time in Qatari ecosystems through 16S rRNA and phaC/phaE gene sequence analyses. Among them, the promising PHA-producing archaeon Haloarcula sp. PLQ exhibited the highest production, reaching a PHB concentration of 496 ± 24 mg L−1 and a cell dry weight of 1109.8 ± 58.6 mg L−1, corresponding to a maximum yield of 44.69 wt % ± 2.13 under optimal conditions. Polymer characterization confirmed the production of poly(3-hydroxybutyrate). In addition, the thermal properties analyzed by TGA (Tonset = 250 °C; Td = 270 °C) and DSC (Tm = 169 °C) confirmed a PHB-like film with thermal behavior comparable to standard PHB. Therefore, future pilot-scale studies on the pure culture of a promising strain for PHA production from renewable feedstocks under non-sterile, batch, or continuous fermentation will be conducted.