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Keywords:

  • PHB;
  • molecular weight;
  • digestion;
  • Escherichia coli;
  • fermentation

Abstract

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%. © 2011 Canadian Society for Chemical Engineering