Co-biosynthesis of exopolysaccharide and poly-3-hydroxybutyrate using a versatile strain Paracoccus sp. TH21-44: Antioxidant potential and fermentation model

Abstract

The sole disadvantage of microbial fermentation products imposes a specific limitation on industrial production, secretion of extracellular exopolysaccharide (EPS) by synergy with intracellular accumulation of polyhydroxyalkanoates (PHAs) can maximize sustainable adaptability. In this study, a high-performing EPS-producing strain TH21-44 was isolated in conjunction with PHAs fermentation. The metabolically diverse bacterium TH21-44 was identified as Paracoccus sp. based on the taxonomic analysis. The genes and metabolic pathways involved in the synthesis of poly-3-hydroxybutyrate (PHB) and EPS were comprehensively characterized through draft genome sequencing. PHAs synthase is classified as class Ⅰ and glycosyl transferases involved in the EPS synthesis have been detected. Foremost, the combined fermentation capacity was further enhanced by adjusting the process parameters. The maximum concentrations of PHB (168.26 mg L⁻¹) and EPS (191.11 mg L⁻¹) were achieved when C/N ratio was established at 15:1, using 10 g L⁻¹ glucose as substrate after 48 h of cultivation. Accordingly, the purified EPS was evaluated for cytotoxicity and oxidative stress with a view to food fields, and obtained PHB properties were detected to fit the appropriate application scenarios. This study established a foundational process for the co-synthesis of EPS and PHB, and offered a novel perspective on leveraging the metabolic potential of functional microorganisms.