Effects of magnetic field exposure patterns on polyhydroxyalkanoates synthesis by Haloferax mediterranei at extreme hypersaline context: Carbon distribution and salt tolerance

The synthesis of polyhydroxyalkanoates (PHAs) by extremophiles presents a promising alternative to mitigate pollution originating from the use of petroleum-based plastics. This study focuses on the impact of different magnetic field (MF) exposure patterns on PHA production and carbon metabolism, aiming to enhance PHA productivity by Haloferax mediterranei within the extreme hypersaline environment and subsequently reducing production costs. Results indicated that under 300 g/L salinity, the highest PHA productivity (1.45 ± 0.06 g/(L d)) and PHA content (65.91 % PHA/cell dry weight) were achieved with 50 mT MF exposure throughout the fermentation period. Continuous exposure to 50 mT MF proved vital for maximizing cell biomass and PHA productivity. Continuous exposure to 50 mT MF enabled Haloferax mediterranei to channel acetyl-CoA towards the PHA synthesis pathway while maintaining growth and proliferation. Correlation analysis further proved the principal role of carbon flux on PHA accumulation. Due to the demand for balancing osmotic pressure, cellular substances were sacrificed to ensure PHA synthesis as anti-salinity substance. Meanwhile, the observed promotion of MF on PHA production, betaine aldehyde dehydrogenase activity, and K⁺ uptake contributed to sustaining cellular activity at 300 g/L salinity. This study provides a non-gene editing approach to enhance PHA productivity.