Recovery of high-value compounds

Fraunhofer IGB develops processes for the production of miscellaneous algal products:

• Natural pigments and highly unsaturated fatty acids (omega-3 fatty acids) from microalgae as food supplements
  
• Triacylglycerides for biodiesel or as feedstock for biobased chemical compounds
• Starch as substitution of agricultural sourced feedstocks for conversion of carbohydrates to bioethanol
• Algae with repellent and antifungal effects useful in organic farming
  

The extracts obtained provide the food, feed and cosmetics industries with natural extracts that have health-promoting and coloring properties, which can then be converted into the corresponding products.

On behalf of interested companies, we will be glad to investigate how you can use the extracts or provide sample quantities.

To obtain valuable products from microalgal biomass and further use of residual biomass, notably employing a cascade, there are some clearly defined requirements. Principally the extraction and separation methods are determined by the chemical character and the market specification such as the required purity of the product.

Additional requirements are:

• Use of wet biomass avoiding energy intensive drying
• Localization of the desired component in the cell and application of specific disruption methods, thereby preserving the functionality of the desired product (i.e. avoiding harmful high temperatures)
• Mild extraction which allows separation of additional components
  

Supercritical fluid extraction for lipophilic compounds

Supercritical fluid extraction, a “natural and green” way of achieving product extraction, has received increasing attention as an important alternative to conventional separation methods because it is simpler, faster, more efficient and avoids the consumption of large amounts of organic solvents, which are often expensive and potentially harmful. The separated product can be converted directly and supplied to the market as a nutraceutical or food ingredient.

Further fractionation

Residual biomass from such processes can be fractionated into additional products like proteins or carbohydrates from microalgal cell walls. To increase polarity of supercritical fluids like scCO₂ ethanol is added, enabling selective extraction of polar glyco- and phospholipids which contain omega-3 fatty acids like EPA. This difference in extraction properties with and without ethanol can even be used for consecutive extraction of unpolar triacylglycerides or carotenoids and polar lipids like omega-3 fatty acids.

Laminarin from microalgae in plant production and human and animal nutrition

Diatoms (rock algae) use (chryso-)laminarin as energy and carbon reservoirs. The polysaccharide is a 1,3/1,6-b-d-glucan that can be used in the food, animal feed and agricultural sectors. Laminarin can also be found in the cell wall of many fungi, including pathogenic species. Since contact with laminarin induces the immune system of vascular plants, the polysaccharide is suitable as plant strengthener. According to the literature, the application of laminarin can reduce infections with Botrytis cinerea or Plasmopara viticola in grapevines by 55 or 75 percent [1]. Laminarin also has an immunomodulatory effect in vertebrates. The immune system in the digestive tract in particular reacts to the contact with laminarin [2].

The MIATEST project is examining the use of laminarin as a biostimulant in viticulture in collaboration with the Landesversuchsanstalt für Wein- und Obstbau Baden-Württemberg and its application in nutrition at the Hohenheim University. To this end, Fraunhofer IGB is examining laminarin production strains, developing a two-step production process and producing laminarin-rich algae biomasses for test purposes.

In addition, laminarin is the subject of the EU-funded MAGNIFICENT BBI project, which is examining the provision of ingredients from microalgae for food, feed and cosmetics. The use of laminarin in juvenile fish rearing is currently being investigated.

Literature

[1] Aziz, A. et al. (2003) Laminarin elicits defense responses in grapevine and induces protection against Botrytis cinerea and Plasmopara viticola. Molecular plant-microbe interactions : MPMI 16, 1118–1128

[2] Stuyven E. et al. (2009) Effect of β-glucans on an ETEC infection in piglets. Spec. Issue 8th Int. Vet. Immunol. Symp. 128 (1–3), 60–66

Eicosapentaenoic acid (EPA) and fucoxanthin

Tailored production of the diatom Phaeodactylum tricornutum results in algae biomass with a high content of polyunsaturated fatty acids such as the omega-3 fatty acid eicosapentaenoic acid (EPA, 20:5 ω-3) and accessory pigments such as fucoxanthin. These ingredients have various health-promoting and anti-oxidative properties, which is why the recovery of the relevant extracts is of great interest to the food, feed and cosmetics industries. EPA for example plays an important role in human cardiovascular and inflammatory diseases like rheumatoid arthritis and multiple sclerosis.

As part of the Bioeconomy Baden-Württemberg project, the diatom P. tricornutum was cultivated in flat-panel airlift reactors (FPA reactors) in semi-continuous operation at different light intensities. The influence of light availability on the composition of biomass with regard to EPA and fucoxanthin content was investigated. In particular, the fucoxanthin content showed a significant dependence on the relative light availability, i.e. the ratio of photon flux (on the reactor surface) to total biomass in the reactor and time (in µmol photons g^-1 of dry mass s^-1). In combination with an optimized and controlled supply of nutrients, we were able to achieve fucoxanthin contents of more than 2 percent (w/w) in terms of dry weight using the FPA photobioreactor. After mechanical cell disruption, both EPA and fucoxanthin can be recovered by means of pressurized liquid extraction (PLE) using suitable organic extraction solvents with yields of over 90 percent. At the Institute of Clinical Nutrition at the University of Hohenheim the extracts were investigated with regard to their nutritional properties: they have a high anti-oxidative and anti-inflammatory capacity.