Lipids and lipid metabolism in eukaryotic algae

Importance of algae oil as a source of biodiesel

The biochemistry and molecular biology of lipid accumulation in oleaginous microorganisms

Evaluation of extraction methods for recovery of fatty acids from lipid-producing microheterotrophs

Nowadays, a wide variety of compounds such as polyphenols, polyunsaturated fatty acids (PUFA), or phytosterols obtained, for example, from wine, fish byproducts, or plants are employed to prepare new functional foods. However, unexplored natural sources of bioactive ingredients are gaining much attention since they can lead to the discovery of new compounds or bioactivities. Microalgae have been proposed as an interesting, almost unlimited, natural source in the search for novel natural functional ingredients, and several works have shown the possibility to find bioactive compounds in these organisms. Some advantages can be associated with the study of microalgae such as their huge diversity, the possibility of being used as natural reactors at controlled conditions, and their ability to produce active secondary metabolites to defend themselves from adverse or extreme conditions. In this contribution, an exhaustive revision is presented involving the research for innovative functional food ingredients from microalgae. The most interesting results in this promising field are discussed including new species composition and bioactivity and new processing and extraction methods. Moreover, the future research trends are critically commented.

Innovative Natural Functional Ingredients from Microalgae

A marine microbe (strain SR21) from the coral reef area of the Yap Islands was isolated by a screening test for polyunsaturated fatty acids and was found to accumulate lipid that contained 22:5n-6 docosapentaenoic acid (DPA) as well as 22:6n-3 docosahexaenoic acid (DHA). Strain SR21 was identified as genusSchizochytrium in Labyrinthulomycota, owing to its ultrastructural character and life cycle, which is composed of vegetative cell, zoosporangium, and zoospore stages. After cultural optimization, both in flask and fermenter, the highest DHA and DPA productivities of 2.0 and 0.44 g/L per day, respectively, were obtained in a medium of 60 g/L glucose and corn steep liquor/ammonium sulfate in a half salt concentration of seawater in fermenter culture at 28°C and pH 4. This productivity was almost twice that obtained with flask culture, indicating its high resistance to mechanical stirring. The lipid extracted from the cell was about 50% of the dry cell weight and was composed of 93% triacylglycerol (TG). DHA content of the lipid was 34% of total fatty acids. The TG profile was simple, and the content of the most dominant TG, 1,3-dipalmitoyl-2-DHA-TG, was 27%. TG that contained DHA and n-6-DPA amounted to 57 and 17%, respectively, of total TG molecules. Strain SR21 was revealed to be an excellent source of microbial DHA and n-6 DPA.

Production of docosahexaenoic and docosapentaenoic acids bySchizochytrium sp. isolated from Yap Islands

The culture conditions for high-yield production of docosahexaenoic acid (DHA) by Schizochytrium sp. strain SR21 were investigated in a fermenter. With increasing carbon (glucose) and nitrogen (corn steep liquor and ammonium sulfate) sources (up to 12% glucose) in the medium, DHA productivity increased without a decrease in growth rate, i.e., 2.0, 2.7, and 3.3 g DHA/L/d with 6, 10, and 12% glucose, respectively. Eventually, 48.1 g dry cells/L and 13.3 g DHA/L were produced in 4 d with 12% glucose. DHA productivity was decreased with 15% glucose, i.e., 3.1 g/L/d. With 12% glucose, the lipid content was 77.5% of dry cells, and DHA content was 35.6% of total fatty acids. The lipid was composed of about 95% neutral lipid and 5% polar lipid. In polar lipids, the contents of phosphatidylcholine (PC), phosphatidylethanolamine, and phosphatidylinositol were 74, 11, and 5%, respectively. The PC profile was simple, 70% of PC molecules were 1-palmitoyl-2-DHA-PC and 1.2-di-DHA-PC. These results indicate that Schizochytrium sp. strain 21 is an excellent source for microbial DHA production, including not only the acid form of DHA but also 2-DHA-PC.

Production of high yields of docosahexaenoic acid by Schizochytrium sp. strain SR21

A process for preparing lipids which contain docosahexaenoic acid (DHA) and/or docosapentaenoic acid (DPA) is disclosed. The process includes the steps of cultivating in a medium a microorganism which belongs to the genus Ulkenia having the ability to produce DHA and/or DPA and recovering the lipids from the culture. The process may further include the step of separating DHA and/or DPA from the lipids.

Process for preparing docosahexaenoic acid and docosapentaenoic acid with ulkenia

The effect of mineral addition on arachidonic acid (AA) production by Mortierella alpina 1S-4 was evaluated. At first, the addition of minerals such as sodium, potassium, calcium, and magnesium was examined in flask cultures, and then the addition of phosphorus with the optimal amounts of the minerals was investigated in a 10-L jar-fermenter. As a result, 1.5% soy flour medium with the addition of 0.3% KH2PO4, 0.1% Na2SO4, 0.05% CaCl2·2H2O, and 0.05% MgCl2·6H2O was found to enhance the AA yield 1.7-fold over that without mineral addition. When 1% yeast extract with the above mineral mixture was used, the AA yield was enhanced 1.35-fold over that without minerals. We also verified that an increase in the polar lipid content occurred in the case of only KH2PO4 addition, and that the above-mentioned increase in the AA yield was due to the minerals themselves, not a pH buffer effect.

http://lib3.dss.go.th/fulltext/journal/j.aocs/j.aocs/1998/no.11/nov998,vol75,no11,p1501-1505.pdf

Enhancement of Arachidonic Acid Production by Mortierella alpina 1S-4

A novel technique for relieving arachidonic acid deficient conditions and maintaining a good fatty acid balance in vivo. Utilizaiton of a DPA-containing material for relieving arachidonic acid deficient conditions and maintaining a good fatty acid balance in vivo; and compositions for relieving arachidonic acid deficient conditions and maintaining a good fatty acid balance in vivo which contain a DPA-containing material in an amount efficacious in relieving arachidonic acid deficient conditions and maintaining a good fatty acid balance in vivo per unit dose.

Toshiaki Yaguchi

Papers

Production of docosahexaenoic and docosapentaenoic acids bySchizochytrium sp. isolated from Yap Islands

Production of high yields of docosahexaenoic acid by Schizochytrium sp. strain SR21

Process for preparing docosahexaenoic acid and docosapentaenoic acid with ulkenia

Enhancement of Arachidonic Acid Production by Mortierella alpina 1S-4

Utilization of material containing docosapentaenoic acid