Differentiation in fatty acid profiles of pigmented and nonpigmented Aurantiochytrium isolated from Hong Kong mangroves

Twenty-five thraustochytrids that belong to the genus Aurantlochytrlum were isolated from subtropical mangroves in Hong Kong. Although they have similar morphological and physiological characteristics, they have different colors on a yeast extract-glucose agar plate, which were largely ignored before. On the basis of the differences in their colony color, 25 Aurantlochytrlum strains were further classified into pigmented and nonpigmented subgroups and their fatty acid profiles were analyzed and compared. In general, nonpigmented Aurantlochytrlum strains were found to contain biomass concentrations and growth yield coefficients statistically higher than pigmented Aurantlochytrlum strains (p< 0.01). Among all isolates, a significantly higher content of polyunsaturated fatty acid (PUFA, 123.41-179.64 mg/g) was found in the nonpigmented Aurantlochytrlum (p<0.01), whereas the pigmented strains contained a higher amount of saturated fatty acids. Docosahexaenoic acid (DHA) was identified as the most abundant PUFA in both nonpigmented and pigmented Aurantlochytrlum. According to the result of principal component analysis, the contents and composition of saturated fatty acids and PUFAs are the major varieties to distinguish these two Aurantlochytrlum groups, especially the contents of C15:0, C13:0, C16:0, C17:0, and DHA. With a rapid growth rate and high DHA yield, the strain from the nonpigmented Aurantlochytrlum group was regarded as the ideal candidate for PUFA production.