Efficient polyhydroxybutyrate production using acetate by engineered Halomonas sp. JJY01 harboring acetyl-CoA acetyltransferase.

Polyhydroxybutyrate (PHB) is a well-known biodegradable bioplastic synthesized by microorganisms and can be produced from volatile fatty acids (VFAs). Among VFAs acetate can be utilized by Halomonas sp. YLGW01 for growth and PHB production. In this study, Halomonas sp. JJY01 was developed through introducing acetyl-CoA acetyltransferase (atoAD) with LacIq-Ptrc promoter into Halomonas sp. YLGW01. The effect of expression of atoAD on acetate was investigated by comparison with acetate consumption and PHB production. Shake-flask study showed that Halomonas sp. JJY01 increased acetate consumption rate, PHB yield and PHB production (0.27 g/L/h, 0.075 g/g, 0.72 g/L) compared to the wild type strain (0.17 g/L/h, 0.016 g/g, 0.11 g/L). In 10 L fermenter scale fed-batch fermentation, the growth of Halomonas sp. JJY01 resulted in higher acetate consumption rate, PHB yield and PHB titer (0.55 g/L/h, 0.091 g/g, 4.6 g/L) than wild type strain (0.35 g/L/h, 0.067 h/h, 2.9 g/L). These findings demonstrate enhanced acetate utilization and PHB production through the introduction of atoAD in Halomonas strains.

Optimization of polyhydroxyalkanoate production in Halomonas sp. YLGW01 using mixed volatile fatty acids: a study on mixture analysis and fed-batch strategy.

Polyhydroxyalkanoate (PHA) is one of the most promising materials for replacing petroleum-based plastics, and it can be produced from various renewable biomass sources. In this study, PHA production was conducted using Halomonas sp. YLGW01 utilizing mixed volatile fatty acids (VFAs) as carbon sources. The ratio and concentration of carbon and nitrogen sources were optimized through mixture analysis and organic nitrogen source screening, respectively. It was found that the highest cell dry weight (CDW) of 3.15 g/L and PHA production of 1.63 g/L were achieved when the ratio of acetate to lactate in the mixed VFAs was 0.45:0.55. Furthermore, supplementation of organic nitrogen sources such as soytone resulted in a ninefold increase in CDW (reaching 2.32 g/L) and a 22-fold increase in PHA production (reaching 1.60 g/L) compared to using inorganic nitrogen sources. Subsequently, DO-stat, VFAs consumption rate stat, and pH-stat fed-batch methods were applied to investigate and evaluate PHA productivity. The results showed that when pH-stat-based VFAs feeding was employed, a CDW of 7 g/L and PHA production of 5.1 g/L were achieved within 68 h, with a PHA content of 73%. Overall, the pH-stat fed-batch strategy proved to be effective in enhancing PHA production by Halomonas sp. YLGW01 utilizing VFAs.