Engineered Halomonas for production of gamma-aminobutyric acid and 2-pyrrolidone

[Display omitted] •Recombinant Halomonas bluephagenesis produced GABA and 2-pyrrolidone.•It also synthesized intracellular PHA as a co-product.•Self-flocculating H. bluephagenesis allowed separation and recycle of the cells.•The above efforts produced the highest reported 880 g/L GABA. Gamma-Aminobutyric acid (GABA) is a derivative of L-glutamate, also a precursor for the synthesis of 2-pyrrolidone, which is a monomer of nylon-4. This study achieved a one-step biosynthesis of GABA and 2-pyrrolidone by Halomonas bluephagenesis overexpressing key genes involved in GABA and 2-pyrrolidone synthesis and deleting GABA degradation genes combined with reducing the degradation of 2-pyrrolidone precursor. The resulting H. bluephagenesis strain WLp07 was employed in whole-cell catalysis, producing 357 g/L of GABA and 72 wt% of PHA. Furthermore, a self-flocculating H. bluephagenesis allowed rapid, convenient recycling of the cells, achieving 880 g/L of GABA over three cycles. Shake flask studies showed that engineered H. bluephagenesis harboring β-alanine CoA transferase was able to synthesized 2-pyrrolidone from GABA. H. bluephagenesis as a chassis of next generation industrial biotechnology (NGIB), demonstrated its diverse ability to produce GABA and 2-pyrrolidone in addition to intracellular PHA.