RESUMO
To be competitive with common plastics, the production costs of polyhydroxyalkanoates (PHAs) have to be minimized. Biotechnological polymer production occurs in aerobic processes; therefore, only about 50% of the main carbon sources and even a lower percentage of the precursors used for production of co-polyesters end up in the products wanted. A second cost factor in normally phosphate-limited production processes for PHAs is the costs for complex nitrogen sources. Both cheap carbon sources and cheap nitrogen sources are available from agricultural waste and surplus materials and make a substantial contribution for minimizing PHA production costs. In this study, fermentations for PHA production were carried out in laboratory-scale bioreactors on hydrolyzed whey permeate and glycerol liquid phase from the biodiesel production using a highly osmophilic organism. Without any precursor, the organism produced a poly[3(hydroxybutyrate-co-hydroxyvalerate)] copolyester on both carbon sources. During the accumulation phases, a constant 3-hydroxyvalerate content of 8-10% was obtained at a total PHA concentration of 5.5 g/L (on hydrolyzed whey permeate) and 16.2 g/L (glycerol liquid phase). In an additional fermentation, an expensive nitrogen source was substituted by meat and bone meal beside the glycerol liquid phase as a carbon source, resulting in a final PHA concentration of 5.9 g/L.
