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ePaper created 2016-03-17, 15:06:18 | version 1.45.01
10 8 CASCADE USE OF MICROALGAE BIOMASS Felix Derwenskus, Ulrike Schmid-Staiger Microalgae – Integrated Use for Food and Feed The fundamental idea of biorefinery concepts is the complete reutilization of biomass by means of fractionation and the ex- traction of various products. Microalgae can produce a large number of substances that are of interest to the food and feed sector. Depending on the species used and the cultiva- tion conditions, they produce large quantities of fatty acids in the form of triacylglycerides (up to 70 percent of dry weight) or proteins (up to 50 percent of dry weight), polar membrane lipids with omega-3 fatty acids (up to 7 percent of dry weight) as well as various carotenoids and phytosterols. The aim is to use these fractions in food production while preserving their technofunctional, nutritional and physiological properties. Due to the great diversity of ingredients and the different cell wall characteristics of various species of microalgae, it is necessary to carry out selective processing of the biomass in order to effectively extract the high-quality nutrients. The objective of the joint research network “Microalgae – Inte- grated Use for Food and Feed” in the Baden-Württemberg Bioeconomy Research Program is to utilize various fractions as completely as possible, in interconnected and cascade use, in order to develop sustainable processes for the bioeconomy. Processing of algae constituents Special requirements apply to processing in the extraction of valuable compounds from algae biomass and the further use of the residual biomass, especially in cascade utilization. Basically the chemical character and the market specifications, for example the required degree of product purity, determine the processing technique. Further requirements are avoiding, as far as possible, an energy-intensive drying step as well as ensuring gentle extraction that both maintains the functional- ity and permits the extraction of further cell components. Working together with the partners in the research network, three strains of microalgae (Phaeodactylum tricornutum, Chlorella vulgaris and Nannochloropsis spec.) were selected that differ fundamentally in cell size, formation of the cell wall and biomass composition. By combining successive extraction processes in various sequences, the objective is to obtain in particular the principal fractions consisting of proteins, polar membrane lipids with omega-3 fatty acids as well as nonpolar triglycerides sequentially from the microalgae biomass – in ad- dition to the high-value components such as carotenoids. Selective and targeted extraction The technique called “Pressurized Liquid Extraction” is mainly employed here; this also permits extraction using wet biomass, as well as e traction by means of supercritical fluids In order to increase the polarity of supercritical fluids, cosolvents such as ethanol can be employed. This results in a selective extraction of polar glycolipids containing eicosapen- taenoic acid EPA; 20:5 ω-3. The different extraction behavior without and with a cosolvent was also used specifically for the sequential, selective extraction of nonpolar triglycerides, carotenoids and polar glycolipids. Currently the process parameters are being optimized with the aim of obtaining fractions that are then examined by the research partners in regard to an application in the food sector. After extraction of the lipophilic valuable compounds the aim is to separate the proteins from the residual biomass, so as to make them avail- able for the production of novel foods by project partners. The residual biomass is suitable for animal feed production. 1 CHEMISTRY 2 triacyl- glycerides carotenoids glycolipids (EPA) proteins high polarity water, organic solventsmedium polarity scCO2 + polar cosolvents (e.g. ethanol) low polarity scCO2 108