En route to economical eco-friendly solvent system in enhancing sustainable recovery of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer

Separation of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] from bacterial cell matter is a critical step in the downstream process with respect to material quality and eco-balance as P(3HB-co-4HB) is widely used for biomedical applications. Therefore, an efficient and eco-based extraction of P(3HB-co-4HB) using a combination of NaOH and Lysol in digesting the non-polymeric cell material (NPCM) digestion is developed. The NaOH and Lysol show synergistic influence on the copolymer extraction at a high purity and recovery of 97 and 98 wt% respectively. The optimized cell digestion method was found applicable to a vast batch of cells containing copolymers from various 4HB monomer compositions. At the largest extraction volume of 100 L, P(3HB-co-4HB) with a purity of 89 wt% was extracted with a maximum recovery of 90 wt%. The method developed has also eliminated the cell pretreatment step. The extraction method developed in this research has not only produced an economic and efficient copolymer recovery but has also retained the copolymer quality, in term of its molecular weight and thermal properties. It demonstrates a practical and promising downstream processing method in recovering the copolymer effectively from the bacterial biomass.