Downstream Processing

Downstream processing (i.e. the processing of biological products) has up till now been a self-contained expertise taught at very few universities and research institutions. Material recovery, however, has now become the most cost-intensive stage in the manufacture of many high-value products. Downstream processing is an interdisciplinary field which mostly involves the engineering sciences, as it is chiefly concerned with thermal or mechanical separation methods. The processing of products, however, requires more than a simple engineering approach concerned with maximising the yield and purity with the fewest possible resources. The safety and reproducibility of the production process must also be guaranteed. The topic of downstream processing is growing in importance for the whole manufacturing industry for biobased products. In the future, methods will be required which will go beyond classical processes (filtration, centrifugation, chromatography), for example electric separation methods, membranes etc. Here, the intelligent combination of different technologies, for example filtration with adsorption, can lead to success.

Supercritical fluids

In order to extract useful materials, supercritical fluids (SCFs) as applied at the Fraunhofer ICT have significant advantages. Under pressure (70 bar), and at a temperature of 35^oC, supercritical carbon dioxide becomes an excellent solvent for the extraction of natural materials from plants (astaxanthine and omega fatty acids from algae). The application of combustible or hazardous solvents is rendered unnecessary. Similar to liquid organic solvents, SCFs are capable of dissolving and extracting low-volatility materials at relatively low temperatures. At only slightly lower densities, SCFs have a diffusion coefficient that is an order of magnitude lower than that of liquids, as well as lower viscosity and therefore a more rapid mass transport behaviour. As a result of these properties, carbon dioxide is ideal for the decomposition of biomass and the extraction of useful substances. Compared to conventional solvents, scCO2 can be more easily and quantitatively separated. As a result it has no detrimental effect on the subsequent biotransformation process.

Application of supercritical fluids at the Fraunhofer ICT