Method for separating, extracting and purifying poly-β-hydroxyalkanoates (PHAs) directly from bacterial fermentation broth

A method for directly separating and purifying polyhydroxyalkanoates in cells from a bacterial fermentation liquid, which comprises the steps of:

• a) physically pretreating a fermentation liquid containing cells to cause the walls of the cells to break;
• b) adjusting the pH value of the pretreated fermentation liquid from step a) to an alkaline condition;
• c) adding anionic surfactant to the solution of step b) and subjecting the solution to agitation;
• d) separating and extracting coagulated precipitate from the solution in step c);
• and
• e) washing and drying the coagulated precipitate,
• wherein the physical pretreatment includes mechanically breaking the cell walls or ultrasonically breaking the cell walls, and wherein steps b) and c) are interchangeable;
• wherein a coagulating agent is added in the step c) and wherein the coagulating agent comprises at least one of sodium polyacrylate, modified starch or polyamine.