Halophyte biorefinery for polyhydroxyalkanoates production from Ulva sp. Hydrolysate with Haloferax mediterranei in pneumatically agitated bioreactors and ultrasound harvesting

The present study tested the outdoor cultivation of Haloferax mediterranei for PHA production from green macroalgae Ulva sp. in pneumatically agitated bioreactors and applied ultrasonic separation for enhanced settling of archaeal cells. Scaled-up cultivation (40 L) yielded maximum biomass productivity of 50.1 +/- 0.11 mg.L(-1)h(-1) with a PHA productivity of 27 +/- 0.01 mg.L(-1)h(-1) and conversion yield of 0.107 g PHA per gram U/va Dw . The maximum mass fraction of PHA achieved in biomass was calculated to be 56% w/w. Ultrasonic harvesting of Hfx. mediterranei cells approached 30% removal at energy inputs around 7.8 kWh.m(-3), and indicated no significant aggregation enhancement by Ca2+ addition. Molecular weight analysis showed an increase in Polydispersity Index (PDI) when the corresponding air velocities were increased suggesting that the polymer was more homogeneous at lower mixing velocities. The current study demonstrated scalable processes for PHA production using Ulva sp. feedstock providing new technologies for halophilic biorefinery.

Automated summary

The study successfully demonstrated the outdoor cultivation of Haloferax mediterranei for PHA production from green macroalgae Ulva sp. using pneumatically agitated bioreactors and ultrasonic separation. Results showed scalable processes with enhanced settling of archaeal cells, providing new technologies for halophilic biorefinery. The research highlighted the importance of optimizing cultivation conditions and harvest methods for efficient production of PHA from renewable sources.