Optimization of Culture Conditions for Growth and Docosahexaenoic Acid Production by a Marine Thraustochytrid, Aurantiochytrium limacinum mh0186 (original) (raw)

2009, Journal of Oleo Science

Long-chain polyunsaturated fatty acids such as arachidonic acid (C 20:4n-6), eicosapentaenoic acid (C 20:5n-3) and docosahexaenoic acid (DHA, C 22:6n-3) are structural components of cell membrane and play important roles in biological functions. DHA is essential for the normal functional development of the retina and brain 1,2) and therefore acceptance of the dietary importance of DHA in human health is increasing. The industrial source of DHA, so far, is from limited natural resources, primarily marine fish oils. As an alternative DHA source to fish oils, DHA derived from microbial production has attracted increasing interest in recent times. There are two commercially available marine microorganisms that produce DHA, a heterotrophic dinoflagellate, Crypthecodinium cohnii, and thraustochytrids. Thraustochytrids (Thraustochytriaceae, Labyrinthulomycetes) are heterotrophic protists that are ubiquitous and abundant in marine and estuarine waters 3,4). They have the ability to produce relatively high biomass and DHA yield, compared with C. cohnii, and several studies concerning DHA production by thraustochytrids have been reported 5). Among thraustochytrids, the genera Thraustochytrium and Schizochytrium are the most investigated groups. Particularly, S. limacinum is known as an excellent DHAproducer and many studies about optimization of DHA production by this strain have been conducted 6-9). Recently, the taxonomic status of the genus Schizochytrium was redefined, and the genus is now classified into three taxa, i.e., Schizochytrium sensu stricto, Aurantiochytrium and Oblongichytrium 10). S. limacinum was reassigned to the genus A. limacinum. In the present study, we determined optimum growth conditions (carbon source, seawater concentration and seawater component) for growth by a marine thraustochytrid strain mh0186, identified as A. limacinum based on the sequence information of the 18S ribosomal RNA gene and 623