Clean Technology 2008
L.S. Serafim, P.C. Lemos, M.A. Prieto, M.A.M. Reis
cheese whey, polyhydroxyalkanoates, recombinant Escherichia coli, Haloferax mediterranei
The replacement of synthetic plastics by biodegradable polymers such as polyhydroxyalkanoates (PHA) is urgent. The final price of these polyesters is higher and the production costs should be decreased. Whey, which is the major by-product of cheese industry and rich in lactose, can serve as a raw material for industrial production of PHA. Some microbial strains can utilize whey for PHA production. Only few microorganisms are able to convert directly lactose into PHA, e.g. recombinant Escherichia coli harbouring PHA biosynthesis genes. This bacterium presents high PHB storage contents (near 90% of cell dry weight). Other bacteria, like Haloferax mediterraneionly use the products of lactose hydrolysis (glucose and galactose) to produce P(HB/HV). These bacteria can also contribute for the reduction of the downstream process costs and complexity since both can disrupt and release the internal PHA granules when the PHA content is very high (E. coli) or the external salinity decreases (H. mediterranei). The results obtained showed that recombinant E. coli has a good potential for PHA producing from cheese whey. On going research is focused on the optimization of PHA production by the selected E.coli strains and on the possibility of H. mediterranei to use lactose for growth.