The use of direct transesterification methods and autoclaving for determining fatty acid yields from dried Philippine thraustochytrids, a potential source of docosahexaenoic acid

Docosahexaenoic acid (22:6n-3, DHA) is a structural fatty acid in biomembranes that is implicated in various aspects of human health. The intake of preformed dietary DHA by humans is largely dependent on marine sources such as fish which are subject to issues regarding sustainability and environmental contamination. Thraustochytrids have gained attention as a potential source of DHA for agricultural and aquacultural feedstocks, and human functional foods and nutraceuticals. In the present study, a dried and powdered strain of cultured Philippine thraustochytrids was examined for nutrient and fatty acid composition before and after sterilization by autoclave. Fatty acid determinations were completed by a conventional extraction plus transesterification method, direct transesterification using convectional heat and direct transesterification using microwave energy with DHA content ranging from 5.2 to 7.4 mg/g dried thraustochytrids. Fatty acid yields by extraction plus transesterification were 77–79% of the yields by direct transesterification. Interestingly, autoclaving had no effect on fatty acid estimates by extraction plus transesterification, but losses in long chain polyunsaturated fatty acids including DHA were observed with autoclaving and direct transesterification analyses. Thraustochytrids are a promising source of DHA, however, quantitation of fatty acids in microalgae is susceptible to sample processing and choice of analytical technique.

► Philippine thraustochytrids were cultured, harvested, dried and powdered.
► Macronutrient and fatty acid composition was determined.
► Fatty acid yields were higher with direct transesterification methods.
► Autoclaving thraustochytrids may decrease polyunsaturated fatty acid levels.