Bio:technical production of poly-beta-hydroxy-butyric acid

摘要

Process for biotechnical production of poly- beta -hydroxy-butyric acid (PHB) or copolymers comprises cultivating a methanotrophic bacterial strain in aqueous nutrient medium with a methane containing gas as sole carbon source and a free oxygen-containing gas under non-sterile conditions, the growth process being carried out continuously and the product-forming process being carried out continuously or discontinuously, followed by extraction of the PHB or copolymer from the resulting biomass using conventional means. Preferably the methanotrophic bacterial strain is preferably Methylocytis spec. ZIMET B 502. The cultivation is carried out e.g. at 20-42 deg C, a pH of 5.2-6.8, a pressure of up to 0.6 MPa and a dissolved oxygen content of 0.5-90 % of the saturation value of air. The concentration of the biomass may be raised during the growth stage by returning part of the biomass after microfiltration into the fermentor. The growth and product forming processes may be carried out alternately. The gas mixture of methane-containing gas and oxygen-containing gas may be recirculated to the process. The methane-containing gas is e.g. pure methane, purified biogas, purified compost gas or natural gas with a content of homologues of methane of less than 15 %.