The isolation of poly(3‐hydroxybutyrate) from recombinant Escherichia coli XL1‐blue using the digestion method

This study examines the isolation of poly(3‐hydroxybutyrate) (PHB) from recombinant Escherichia coli XL1‐blue pBHB2 OLD‐2 harbouring the PHB biosynthesis gene. Six types of commercial surfactants (Emal 10P, Emal AD‐25, Emal S PASTE, Neopelex S‐S, Triton X‐100 and cetyl trimethyl ammonium bromide (CTAB)) were screened for PHB isolation by solubilising non‐polymer cellular material (NPCM) in the cell. Emal 10P, Emal AD‐25, Emal S PASTE and Triton X‐100 are suitable surfactants for PHB isolation. Factors such as the reaction temperature, reaction time, ratio of NPCM/surfactant and pH were investigated to achieve optimum conditions. For 80% of the PHB content in dry cells, the purity and recovery of the obtained PHB was 98% and 99% when 0.67 of NPCM/Emal S PASTE was used at 70°C for 30 min. The cost of the used surfactant is below 0.5 USD/kg (PHB). The pretreatment and multistage digestion method must be combined when the PHB content is lower than 80%.