Natural substances from blue-green algae
Unusual metabolic products often characterise algae and blue-green algae (cyanobacteria). For example, the algae oils of the fat droplets contain high concentrations of polyunsaturated fatty acids (w-6, w-3). Therefore, they are of interest as a substitute for fish oils with decreasing quantity and increasing price due to reduced catches. Algae are also a hoard of rare molecules. Blue-green algae, in particular, have also fallen into disrepute due to very toxic molecules that - although only formed in low concentrations - can become a danger to humans and animals during algal blooms in bodies of water. Neurological deficits and sudden cardiovascular diseases are associated with them. So it is anticipated that blue-green algae toxins have long been in the sights of pharmaceutical research.
Cultivation of algae is regarded as another strategy in the Renewable Resources field. Within the framework of a project funded by the EU (ZIEL-ETZ , Interreg) and coordinated by the Chair of Organic-Analytical Chemistry, under the aspect of mass cultivation, the value-added chain, the complete utilisation of all produced material, theCO2 balance, as well as some basic questions about genome and ingredients, some explosive topics of blue-green algae research should, therefore, be taken up and considered. To this end, partners from the Czech Academy of Sciences at the Algae Research Centre Algatech in Trebon, members of the University of Regensburg, and the Technical University of Munich at the joint location in Straubing have been conducting research for three years.
Of the numerous topics, only the areas that working groups of the HSWT worked on are presented here in more detail. The working groups Pavel Hrouzek from Trebon and Herbert Riepl (organic-analytical chemistry) dealt with medically usable metabolic products. Minutissamides, which are toxic against some pathogenic fungi, were isolated from the cultivation broths of Cylindrospermum Spp. However, the very ones that would be most suitable are present in the lowest concentrations. It was suspected that by chemically altering the side chains of this cyclopeptide, molecules could be obtained which are so much more effective that it is no longer necessary to isolate the low concentration substance. Consequently, various reactions were applied to minutissamide A, a ketone with little activity but which can be isolated in larger quantities, considerably lengthen the fatty acid chain. And indeed, it was possible to find a variant with a maintained toxicity towards the pathogenic fungi, and concurrently the tolerance towards human cells decreased considerably.
The primary aim of the sustainability analysis was to evaluate the life cycle assessment of a microalgae biorefinery compared to a plant- and petroleum-based reference system. Two promising scenarios in which the microalgae biorefinery could reduce global GHG emissions and dependence on fossil fuels were identified: (A) stand-alone scenario with fully renewable electricity mix, woodchips as heat source and CO2 waste gas as carbon source, and (B) integrated scenario in which microalgae cultivation was combined with sewage sludge fermentation. Both scenarios have correspondent features: (i) an additional carbon source, (ii) renewable energy sources, and (iii) technological improvements for drying, digestion and membrane filtration. The integrated scenario (B) showed better results in the target region of the Bavarian-Czech border area than the stand-alone scenario due to a better availability of heating in the winter months.
The developed approach of backward LCA analysis opens up new possibilities for developing new technologies, allowing to identify main parameters and their desired value ranges for planned biorefineries in advance.
