Method for the preparation of polyhydroxybutyrate

A method for preparing polyhydroxybutyrate (PHB) or a salt thereof, comprising:

• incubating Bacillus megaterium QM B1551 in a culture medium comprising a mixture of agri-food wastes, said Bacillus megaterium QM B1551 producing polyhydroxybutyrate;
• separating or collecting the polyhydroxybutyrate from the culture medium,
• wherein the mixture of agri-food wastes comprises solid agri-food wastes including orange peels, wheat bran, and rice husks and liquid agri-food wastes including olive oil vegetation waters and pomace, and
• wherein said solid agri-food wastes and liquid agri-food wastes are present in a weight ratio of 35:65, based on the total weight of the mixture,
• wherein said separated or collected polyhydroxybutyrate has a molecular weight between 7.6 and 9.2 MDa, and
• wherein said separated or collected polyhydroxybutyrate is obtained with a yield of not less than 83% by weight based on a dry cell mass weight of the mixture.