Algae and blue-green algae (cyanobacteria) are often characterized by unusual metabolites. The algae oils in the lipid droplets contain a high concentration of polyunsaturated fatty acids (w-6, w-3). There is, therefore, interest in them as an alternative for fish oils, the quantity of which is falling and the price of which is rising owing to reduced catches. Algae are also a treasure trove of rare molecules. Blue-green algae in particular have fallen into disrepute due to their highly toxic molecules, which – although they are only formed in low concentrations – can pose a threat to humans and animals during algae blooms in bodies of water. They are associated with neurological deficits and sudden cardiovascular diseases. It is no surprise, then, that blue-green algae toxins have long been the focus of pharmaceutical research.
Algaculture is seen as a further strategy in the field of renewable raw materials. As part of a project funded by the EU (ZIEL-ETZ, Interreg) and coordinated by the Professorship for Organic-Analytical Chemistry, some controversial topics in blue-green algae research should therefore be considered from the perspective of mass cultivation, the value chain, the full use of all material produced and the carbon footprint along with some basic questions about genomes and ingredients. To that end, partners from the Czech Academy of Sciences at the Algatech algae research centre in Trebon, members of the University of Regensburg and the Technical University of Munich have been conducting research for three years at the joint location in Straubing.
Of the many topics investigated, only the areas that were worked on by HSWT working groups are presented in more detail here. The working groups of Pavel Hrouzek from Trebon and Herbert Riepl (organic-analytical chemistry) dealt with metabolites that can be used in medicine. The minutissamides, which are toxic to some pathogenic fungi, were isolated from the broth cultures of Cylindrospermum Spp. The ones that would be most suitable, however, are the ones that are present in the lowest concentration. It was suspected that a chemical change in the side chains of this cyclopeptide would produce molecules with such increased effectiveness that there was no longer any need to rely on isolation of the low-concentration substance. Consequently, various reactions that significantly increase the length of the fatty acid chain were applied to minutissamide A, a less active ketone, but one which can be isolated in larger quantities. A variant was found in which the toxicity to the pathogenic fungi was retained while the tolerance to human cells was considerably reduced.
The objective of the sustainability analysis was primarily to evaluate the environmental performance of a microalgae biorefinery compared to a vegetable oil and petroleum-based reference system. Two promising scenarios were identified in which the microalgae biorefinery could reduce global GHG emissions and dependence on fossil fuels: (A) a standalone set-up with a completely renewable fuel mix, woodchips as the heat source and CO2 exhaust gas as the carbon source, and (B) an integrated set-up in which microalgae cultivation was combined with sewage sludge fermentation. Both scenarios have aspects in common: (i) an additional carbon source (ii) renewable energy sources and (iii) technological improvements for drying, digestion and membrane filtration. The integrated scenario (B) produced better results in the target region of the Bavarian-Czech border than the standalone scenario owing to better availability of heating in the winter months.
The approach developed – backward analysis of environmental performance – opens up new possibilities for the development of new technologies to enable advance identification of key parameters and their desired value ranges for planned biorefineries.