Microalgae as source of polyunsaturated fatty acids for aquaculture

The therapeutic significance of polyunsaturated fatty acid (PUFA) especially docosahexaenic acid (DHA), eicosapentaenoic acid (EPA) and arachidonic acid (AA) has been demonstrated by recent clinical and epidemiological studies. Fish oils are the major commercial source of long chained ?3 PUFA. Global production of farmed fish and shell fish has more than doubled in the past two decades, trends toward intensification and greater control over nutritional input resulting in increased demand for wild fish for feed. Feed is the largest production cost for commercial aquaculture (e.g. most farming of salmon, other marine finfish, and shrimp), and thus improving feed efficiency in industrial systems is already a priority. Moreover, fishmeal prices have risen in real terms in the past three decades and are likely to increase further with continued growth in demand. The possible decline of commercial fish stocks calls for research in alternative sources of PUFA. Considerable evidence has indicated that ?3 fatty acids in fish oils actually derive from zooplankton that consumes algae. Further the microalgae may have superior lipid stability compared to traditional PUFA because they are naturally rich in antioxidant carotenoids and vitamins and because lipids are microencapsulated by the algae cell wall.