Biosynthesis of polyesters in bacteria and recombinant organisms

Abstract Many bacteria are able to synthesize polyesters of hydroxyalkanoic acids (PHA), which occur as insoluble cytoplasmic inclusions in the cell and can contribute significantly to the cellular dry matter. More than 100 different hydroxyalkanoic acids have been detected as constituents in PHA. This article summarizes strategies and possibilities to obtain these biodegradable and thermoplastic/elastomeric polymers by fermentation of wild-type bacteria as well as of mutants and recombinant strains from renewable resources, waste substrates or special precursor substrates. In addition, in vitro biosynthesis of PHA employing the purified polymerizing enzyme (PHA synthase) is described. Throughout analysis and cloning of the bacterial PHA biosynthesis genes enabled scientists to also establish this pathway in non-PHA producing eukaryotic organisms such as yeast, plants and animals. This will allow new processes for cheap and economic production of PHA.