Purification and Characterization of Polyhydroxyalkanoate Synthase from Extremely Halophilic Archaeon Haloferax mediterranei: Key Enzyme of Biodegradable Plastic Synthesis

The biosynthesis of polyhydroxyalkanoate (PHA) biopolymer is highly dependent on the activity of a key enzyme, PHA synthase (PhaC). The halophilic archaeon <i>Haloferax mediterranei</i> can accumulate large amounts of PHAs from different carbon sources under non-sterilized conditions. In this study, a PhaC enzyme from <i>H. mediterranei</i> was produced and subsequently partially purified by ion exchange chromatography. The protein was visualized by SDS-PAGE, with a subunit molecular mass of 56.4 kDa. The purified enzyme converts hydroxybutyryl CoA molecules into PHA, being optimally active at pH 10.0 and pH 8.0. The PhaC was thermoactive in the range of 30 °C to 70 °C, with maximum activity registered at 50 °C. The enzyme was confirmed to be haloalkaliphilic (active at pH > 7.0 and high salt concentration) and exhibit a degree of stability at 25 °C for 24 h.