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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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Halomonas bluephagenesis has been engineered to produce flexible copolymers P34HB or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) from glucose and petrol-chemical precursor, γ-butyrolactone. Herein, gene cluster aldD-dhaT was constructed in recombinant H. bluephagenesis for catalyzing 1,4-butanediol (BDO) into 4-hydroxybutyrate, which could grow to 86 g L -1 dry cell mass (DCM) containing 77 wt% P(3HB-co-14 mol% 4HB) in 7-L bioreactor fed with glucose and bio-based BDO. Furthermore, 4HB monomer ratio could be increased to 16 mol% by engineered H. bluephagenesis TDH4-WZY254 with defected outer-membrane. Upon deletion of 4HB degradation pathway, followed by aldD-dhaT integration, the resulted H. bluephagenesis TDB141ΔAC was grown to 95 g L -1 DCM containing 79 wt% P(3HB-co-14 mol% 4HB) with a BDO conversion efficiency of 86% under fed-batch fermentation. Notably, 4HB molar ratio can be significantly improved to 21 mol% with negligible effects on cell growth and P34HB synthesis by adding 50% more BDO. This study successfully demonstrated a fully bio-based P34HB effectively produced by H. bluephagenesis., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Cadaverine, a derivative of l-lysine, has been used as a monomer for the synthesis of bio-based nylon-5,6. This study engineered Halomonas bluephagenesis TD1.0 by blocking the feedback inhibition, overexpressing the key l-lysine synthesis genes, strengthening the l-lysine export system and increasing the supply of oxaloacetate for production of l-lysine in the supernatant and PHB in the cells. Subsequently, cadaverine biosynthetic pathway was constructed in H. campaniensis LC-9 to improve the efficiency of de novo cadaverine biosynthesis which combines l-lysine producing H. bluephagenesis TDL8-68-259 and cadaverine producing H. campaniensis LC-9-ldcC-lysP. When H. campaniensis LC-9-ldcC-lysP was used as a whole cell catalysis for cadaverine production, the conversion efficiency of l-lysine to cadaverine reached 100% in the presence of 0.05% Triton X-100 for cell membrane permeability enhancement, resulting in 118 g L -1 cadaverine formed in the fermentor. Thus, Halomonas spp. have been successfully constructed for l-lysine and cadaverine production., (Copyright © 2022 Elsevier Ltd. All rights reserved.)