G. Braunegg*, R. Bona, C. Hermann, P. Horvat, M. Koller, M. Kroutil,
J. Martinz, J. Neto, L. Pereira, and P. Varila
Graz University of Technology, Institute of Biotechnology and Bioprocess Engineering, A-8010 Graz, Petersgasse 12, Austria
Keywords: glycerol liquid phase, meat & bone meal, polyhydroxyalkanoates, whey
Ongoing studies do not only aim at sustainable aspects of polyhydroxyalkanoates (PHAs), but also consider economic factors that until today are the major disadvantages in replacing common materials [1, 2]. In order 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 are 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 southern countries a variety of different surplus carbon sources are available (e.g. molasses, starch, cellulose) in high quantities for sustainable process development. For biopolymer production in Europe the situation differs, the availability of defined cheap carbon is rather restricted. Here substrates like cheese-whey or glycerol from biodiesel production are of interest.
According to the results of this work, the biotechnological utilization of both agricultural surplus products, whey and GLP, as cheap carbon sources for production of the high price product PHA is possible. Together with the application of hydrolyzed meat and bone meal that has been proved by the authors to be a suitable complex nitrogen- and phosphorus source, production costs can be minimized considerably. Because of totally different molecular masses depending on the substrate (high Mw on whey hexoses, low Mw on GLP), a broad spectrum of biopolyesters with different properties are available starting from surplus products as raw materials. The production of 3-hydroxyvalerate 3-HV in a constant amount from both cheap substrates makes the process economically even more interesting and improve the product qualities.
