Poly(3-hydroxybutyrate) biosynthesis under non-sterile conditions: Piperazine as nitrogen substrate control switch.

Poly(3-hydroxybutyrate) (PHB), as a kind of bioplastics for sustainable development, can be synthesized by various microorganisms, however, the high cost of its microbial fermentation is a challenge for its large-scale application. In this study, piperazine degrading strain, Paracoccus sp. TOH, was developed as an excellent chassis for open PHB fermentation with piperazine as controlling element. Whole-genome analysis showed that TOH possesses multi-substrate metabolic pathways to synthesize PHB. Next, TOH could achieve a maximum PHB concentration of 2.42 g L−1, representing a yield of 0.36 g-PHB g−1-glycerol when C/N ratio was set as 60:1 with 10 g L−1 glycerol as substrate. Furthermore, TOH could even synthesize 0.39 g-PHB g−1-glycerol under non-sterile conditions when piperazine was fed with a suitable rate of 1 mg L−1 h−1. 16S rRNA gene sequencing analysis showed that microbial contamination could be effectively inhibited through the regulation of piperazine under non-sterile conditions and TOH dominated the microbial community with a relative abundance of 72.3% at the end of the operational period. This study offers an inspired open PHB fermentation system with piperazine as the control switch, which will realize the goal of efficient industrial biotechnology as well as industrial wastewater treatment. • Poly(3-hydroxybutyrate) synthesis capability was identified in Paracoccus sp. TOH. • TOH could utilize various carbon sources for PHB biosynthesis. • A PHB yield of 0.36 g-PHB g−1-glycerol with PHB titer of 2.42 g L−1 were observed. • Piperazine acts as controlling element for the open PHB fermentation system. • Microbial contamination was effectively inhibited under non-sterile conditions. [ABSTRACT FROM AUTHOR]