Engineering of bacteria for Polyhydroxyalkanoates production from waste material containing lactose.

Polyhydroxyalkanoates [P(HA)s] are accumulated in a number of bacteria as intracellular carbon and energy storage materials under limited nutrient conditions. P(HA)s have generated significant commercial interest due to their application as biodegradable thermoplastics that can be produced using renewable resources. The use of cheap renewable carbon sources, specially originated from industrial or agricultural by-products, can provide a way to reduce the price. Cheese whey, a by-product of the dairy industry, is available in large amounts from cheese manufacture, also causing disposal problems in EU. We report here the construction of recombinant strains and data related to their growth and polyester accumulation in lactose, hydrolyzed whey and directly in whey permeate, the fraction containing concentrated lactose obtained by ultrafilatration. Cupravidus necator, a gram-negative, facultative chemolithototrophic bacterium, has been intensively investigated for almost 50 years and recently the genome sequence of strain H16 was published. Strain DSM 545, able to produce a range of interesting polymers including polyamides such as cyanophycin, was chosen as the model organism since it is especially known to accumulate high amounts of P(HA)s. However, this strain can not utilize lactose as carbon source, therefore we constructed a genetically modified strain able to use this disaccharide. We described here the introduction of the β-galactosidase gene from Escherichia coli using different plasmids and the insertion of this gene in the chromosome of DSM 545. All the modified strains were able to grow and produce poly-3-hydroxybutyrate directly from lactose, hydrolyzed whey and whey permeate.