Polyhydroxyalkanoates(PHAs): sustainable biopolyester production

Abstract

Microbial polyhydroxyalkanoate (PHA) reserve polymers are interesting polyesters that can be sustainably produced by biotechnological means from a variety of renewable substrates. By feeding cosubstrates to selected cultures of prokaryotic microorganisms composition, structure and therefore physical properties of the PHAs can be influenced during their biotechnological production. Cheap substrates stemming from agricultural waste and surplus streams have to be used in order reduce product costs to a level similar to that of conventional plastics. Continuous production in combinations of a stirred tank reactor for microbial growth and a tubular plug flow reactor for PHA accumulation in the microbial biomass form the ideal production system. PHA is accumulated within the producing cells and has to be extracted. A system of chloroform, ethanol and water allows reusing the extracting solvent chloroform without prior redistillation.