Optimization of poly(-3-hydroxybutyrate-co-3-hydroxyvalerate) synthesis using sodium acetate as a carbon source by Rhodococcus sp. lz1 via response surface methodology.

This study examines Rhodococcus sp. lz1, a bacterium isolated from activated sludge in propylene oxide saponification wastewater, which can utilize diverse carbon sources to produce high yields of Poly(-3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Owing to the lack of lipopolysaccharides (LPS), this bacterium does not trigger significant immunogenic responses, increasing its application potential. Plackett-Burman and Box-Behnken design experiments were conducted, following initial optimization using single-factor conditions. The optimal conditions determined through response surface methodology was a carbon source concentration of 6.8 g/L, inoculum amount of 6.9 %, and seed age of 11 h. Under these conditions, strain lz1 achieved a PHBV yield of 41.87 %, representing an 8.78 % increase. Nuclear magnetic resonance analysis confirmed that the synthesized polyhydroxyalkanoates (PHA) was PHBV. Thermogravimetric analysis (TGA) showed a T of 270 °C, while gel permeation chromatography (GPC) indicated a polydispersity index (PDI) of 2.43, demonstrating good ductility and high thermal stability.