Optimization of poly(3-hydroxybutyrate) extraction from Cupriavidus necator DSM 545 using sodium dodecyl sulfate and sodium hypochlorite

Abstract

Poly (3-hydroxybutyrate) (P(3HB)), a type of bioplastic, has been attractive as an alternative source to replace petroleum-based plastics. Generally, P(3HB) is produced from Cupriavidus necator DSM 545 under some nutrient-limiting and oxygen-limiting conditions. In this work, the batch production of P(3HB) was conducted in shake flask culture at 30 °C and 250 revolutions per minute. The results showed that the concentration of biomass, the P(3HB) yields from substrate and biomass, the volumetric production rate of P(3HB) and the concentration of P(3HB) were maximized at 40 hr of cultivation (5.845 ± 0.375 g/L, 0.128 ± 0.006 g/g, 0.229 ± 0.030 g/g, 0.031 ± 0.001 g/L hr and 1.335 ± 0.087 g/L, respectively). As P(3HB) is accumulated intracellularly in the bacterial cells, P(3HB) recovery is an essential process for industrial P(3HB) production. This work focused on the optimization of P(3HB) extraction using sodium dodecyl sulfate (SDS) and sodium hypochlorite (NaOCl) in an experiment designed using the Taguchi method. The results showed that the optimal conditions for the maximum P(3HB) recovery of 78.70% were 0.5% w/v SDS consecutively combined with 6% v/v NaOCl, while the concentration of sodium hypochlorite had a greater effect on P(3HB) recovery compared to SDS. The
P(3HB) optimally extracted was analyzed using Fourier-transform infrared spectrophotometry and differential scanning calorimetry to investigate structural and thermal properties, which were compared to those of commercial P(3HB). The findings could be useful for scaling-up industrial P(3HB) recovery.