The invention relates to an optimized method for cultivating
microorganisms of the genus Thraustochytriales, according to which the
microorganisms are cultivated in a low salt medium without adding sodium
salts and chloride salts, the total salt content being less than 3.5 g/L
(corresponding to less than 10 percent of sea water salt content),
whereupon the PUFAs are isolated from the microorganisms and/or the
medium. The invention especially relates to novel optimized media having
a substantially reduced total salt content, above all a particularly
reduced NaCl content. The production of PUFAs can be substantially
improved and significantly simplified by using a novel combination of
different salts as a media composition in which the overall weight ratios
of ions do not exceed 1.75 g/L. Furthermore, said medium preferably
contains no added sodium salt and chloride salt at all, which helps
prevent environmental damages caused by wastewaters containing salt.