Dead Sea water as a sustainable source for the production of microbial bioplastics polyhydroxyalkanoates by halophiles

The Dead Sea is a unique salt-saturated water body. This work utilized the Dead Sea water (DSW) as a medium instead of fresh water for the biosynthesis of polyhydroxyalkanoates (PHAs) by Haloferax mediterranei. The intracellular content of PHAs reached a maximum (6.35 %) at 40 % DSW. An artificial DSW media that mimics the DSW composition was prepared and used for PHAs production by H. mediterranei. The cell dry mass (CDM) and PHAs comcentration (32.61 g L⁻¹ and 4.56 g L⁻¹, respectively) were significantly higher than the results obtained from the reported H. mediterranei highly saline medium. The PHAs production was scaled-up to fed-batch utilizing no-cost date fruit waste and resulted in CDM and PHA concentration of 46.89 g L⁻¹ and 12.77 g L⁻¹, respectively under non-sterile conditions. H. mediterranei accumulated poly-3-(hydroxybutyrate-co-9 %-hydroxyvalerate) with molar mass 916.0 kDa and melting point at 143.2 °C. These results indicate the production of a high-quality biopolymer.