Co-production of biofuel, bioplastics and biochemicals during extended fermentation of Halomonas bluephagenesis

Halomonas bluephagenesis TD1.0 was engineered to produce the biofuel propane, bioplastic poly-3-hydroxybutyrate (PHB), and biochemicals mandelate and hydroxymandelate in a single, semi-continuous batch fermentation under non-sterile conditions. Multi-product separation was achieved by segregation of the headspace gas (propane), fermentation broth ([hydroxy]mandelate) and cellular biomass (PHB). Engineering was performed by incorporating the genes encoding fatty acid photodecarboxylase (CvFAP) and hydroxymandelic acid synthase (SyHMAS) into a H. bluephagenesis hmgCAB cassette knockout to channel flux towards (hydroxy)mandelate. Design of Experiment strategies were coupled with fermentation trials to simultaneously optimize each product. Propane and mandelate titres were the highest reported for H. bluephagenesis (62 g/gDCW and 71 ± 10 mg/L respectively) with PHB titres (69% g/gDCW) comparable to other published studies. This proof-of-concept achievement of four easily separated products within one fermentation is a novel achievement probing the versatility of biotechnology, further elevating H. bluephagenesis as a Next Generation Industrial Biotechnology (NGIB) chassis by producing highly valued products at a reduced cost.