Gamma-irradiation enhancement of polyhydroxyalkanoate production in <i>Halomonas mongoliensis</i> AL-ARS: toward sustainable biopolymer development

Polyhydroxyalkanoates (PHAs) are eco-friendly, biodegradable thermoplastics that have the potential to replace conventional plastics with sustainable biopolymers for several applications. This study aimed to isolate and identify halotolerant strains and to optimise the parameters influencing PHA production using response surface methodology. Furthermore, enhancing PHA production and evaluating the effects of low-dose gamma irradiation on <i>Halomonas mongoliensis</i> AL-ARS. Fifteen bacterial isolates were screened using Sudan Black B for PHA production. The most efficient isolate was <i>Halomonas mongoliensis</i> AL-ARS, identified through morphological, biochemical, and molecular techniques. Response surface methodology using Plackett-Burman and central composite design models is used to optimise factors influencing PHA synthesising. Additionally, the effect of low-dose gamma irradiation was examined. The purified PHA polymer was structurally characterised using FTIR, XRD, and ¹H-NMR. Glucose was the optimal carbon source, while minimal salt media was the most suitable media for PHA production. The best production conditions (10 g/L glucose, 40.5°C, 6.5 days, 2.5% inoculum) yielded 0.0960 g/L of PHA. Remarkably, gamma irradiation at 0.5 kGy significantly increased PHA production by 76%, confirming its role as a stress-inducing factor and highlighting irradiation's potential to overcome production bottlenecks. Structural analyses confirmed the purified polymer as a standard PHA. This work is the first study highlighting the integration of gamma irradiation with a statistical optimisation to boost PHA biosynthesis using <i>Halomonas mongoliensis</i> AL-ARS, a halophilic strain with no previous study on PHA improvement, presenting a scalable strategy for sustainable, eco-friendly, cost-effective bioplastic production, and bridging the gap between lab-scale and industrial application.