Polyhydroxyalkanoates production from waste material containing lactose

With the aim of polyhydroxyalkanoates (PHA) production, a study of the growth and polymer accumulation of a modified Wautersia eutropha DSM 545 (ex Ralstonia eutropha) in lactose-containing waste material was carried out. Since the wild type strain is a good PHA producer, but is not able to hydrolize lactose, a mutant was obtained (mRePT), able to grow on lactose and to produce PHA. The mutation was obtained by the introduction of the lacZ operon directly into the chromosome. Due to the fact that a gene has to be knocked-out for the introduction of the operon, one of the three intracellular PHA depolymerases (phaZ1) of W. eutropha was chosen. A lower consumption of the polymer and a higher yield of PHA were therefore expected. Knock-out of phaZ1 was achieved by isolating a fragment of this gene and interrupting it with a cartridge containing the lacZ, lacI and lacO genes and a synthetic promoter (costructed based on the consensus of a number of naturally occurring promoters). The modified gene was transferred into W. eutropha by gene replacement. Studies of growth and polymer production of the GM strain in lactose as carbon source will be presented.