Production of Polyhydroxyalkanoates (PHAs) by Pseudomonas reptilivora B-6bs Using Glucose as a Carbon Source

Abstract

Plastics are a serious environmental problem because of their recalcitrant and environmentally toxic physicochemical properties. Biopolymers are efficient and environmentally friendly alternatives to petrochemical plastics. Polyhydroxyalkanoates (PHA) are biopolymers produced by some microorganisms (Cupriavidus necator, Pseudomonas putida, etc.) under stress and excessive sources of carbon. PHA is a viable alternative to plastics; however, it has a high production cost that is ten times greater than that of petroleum-derived plastics. This research aimed to evaluate the effects of glucose concentration as a carbon source and ammonium sulfate as a nitrogen source on the PHA produced by Pseudomonas reptilivora. After fermentation, the best treatment consisted of six treatments (20 g/L glucose and 1 g/L ammonium sulfate), and the specific growth rate (µ = 0.0546 h⁻¹), productivity rate (rPHA = 0.0257 g/L·h), product/substrate yield (Y_P/S = 0.1305 g/g) and average partitioning rate (δ = 0.0787 h⁻¹) were determined. In treatment 3 (10 g/L glucose and 1 g/L ammonium sulfate), the best biomass/substrate yield (Y_X/S) was 0.2815 g/g. The highest PHA production was 1.544 ± 0.0331 g/L when 20 g/L glucose and 1 g/L ammonium sulfate were used, which was statistically significant, with P-values of 0.0005 and 0.0037, respectively, at the 95% confidence level, suggesting that higher glucose concentrations and higher ammonium sulfate concentrations that increase cell growth are the best conditions for PHA production.