Abstract: The invention relates to a method for enhancing levels of polyunsaturated fatty acid levels in thraustochytrid fungi, using media supplemented with polyvinyl pyrrolidone (PVP) to increase viscosity and which comprises: (a) providing a thraustochytrid fungus strain NIO-TH 21, corresponding to the species Ulkenia radiata Gaertner, being the culture with Accession No. AB22115 of the National Institute of Bioscience and Human-Technology, Japan; (b) inoculating the above said strain in a culture medium; (c) growing the culture for 2 days at a temperature ranging from 25 to 30° C.; (d) obtaining the cultures for use as innoculum using the above said medium to inoculate a medium with different concentrations of polyvinyl pyrrolidone (PVP); (e) growing the culture separately for 2 to 5 days at a temperature ranging from 25 to 30° C.; and (f) harvesting the cells from the above culture by centrifugation and extracting the enhanced amounts of docosahexaenoic acid (DHA) and eicosapentaenoic acids (EPA).