NOVELTY - Microbial biomass composition is obtained by performing heterotrophic fermentation. The biomass has fatty acid profile in which the ratio of eicosapentaenoic acid (EPA) to arachidonic acid (ARA) is 11:1 or more, and ratio of EPA to total co-concentrating fatty acid is 8:1 or more.    USE - The microbial biomass composition is useful for producing enriched or purified fatty acid composition, and fatty acid composition. The enriched or purified fatty acid composition is useful for treating cardiovascular disorder or obesity related condition. The fatty acid composition is useful in product for human or animal consumption. The microbial biomass composition is useful for producing highly pure EPA composition comprising EPA at a concentration of 60%, 70%, 80%, 90%, 95% or 97% with respect to total weight of fatty acids (all claimed), and pharmaceutical. The pharmaceutical is in the form of tablet, capsule, liquid or solution for treating diseases including diabetes (type I, and type II), glycaemic disorders diabetes-associated hypertension, cancer, cardiovascular disorder, obesity related condition, and autoimmune diseases, preferably cardiovascular disorder, or obesity related condition.    ADVANTAGE - The microbial biomass composition produces EPA composition with high purity and high concentration at high yield cost-effectively, and does not require extraction and purification steps to recover fatty acids, thus suitable for industrial production. The produced EPA composition has high degree of EPA/ARA ratio, is free of physiochemically or structurally similar molecules, and comprises lower level of undesirable fatty acids (e.g. omega-3 and omega-6 fatty acids) capable of altering the beneficial health level of EPA.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) method (M1) for producing the above-mentioned microbial biomass, involves (a) heterotrophically culturing a microorganism, and (b) recovering the microbial biomass;    (2) microbial biomass obtained or obtainable by the above-mentioned method (M1);    (3) fatty acid composition obtained or obtainable by the above-mentioned method (M1);    (4) enriched or purified fatty acid composition obtained or obtainable by the above-mentioned method (M1);    (5) diatom grown heterotrophically comprising EPA and ARA in a ratio of at least 14:1, where EPA forms at least 1.5 weight/weight% of the dry weight of the diatom;    (6) lipid mixture derived from the above-mentioned diatom;    (7) fatty acid mixture derived from the above-mentioned diatom;    (8) method (M2) for producing the above-mentioned diatom, involves (a) culturing diatoms in heterotrophic culture containing a nutrient solution comprising (i) an organic carbon source at an initial concentration of at least 0.5 M carbon, (ii) a molar ratio of organic carbon to nitrogen not greater than 30:1, and (iii) a non-limiting source of bioavailable silicon, and (b) recovering the diatom from the heterotrophic culture;    (9) method (M3) for producing lipid material containing EPA, involves (a) culturing diatoms in a fermenter containing a nutrient solution having a molar ratio of available carbon to nitrogen of 1:1-30:1, and a source of bioavailable silicon, (b) maintaining the temperature of the nutrient solution at 12-35 degrees C, and the pH at 7-8.7, (c) harvesting diatoms from the fermenter, and (d) recovering lipid material containing EPA from the harvested diatoms; and    (10) method (M4) for producing the above-mentioned diatom, involves culturing heterotrophic diatoms under conditions designed to induce permanent phenotypic change, and (b) screening the resultant population of diatoms for isolates in which the ratio of EPA and ARA is at least 14:1.