Microbial oil, production method for microbial oil, concentrated microbial oil, and production method for concentrated microbial oil

A microbial oil comprising:

• arachidonic acid (ARA) or Mead acid in a fatty acid alkyl ester form or in a free fatty acid form at a content of at least 50% by weight of the total weight of fatty acids in the microbial oil;
• and
• one or more trans isomers of ARA or Mead acid at a total content of 0.0001% to 3.0% by weight of the total weight of fatty acids in the microbial oil,
• wherein the microbial oil comprises a mixture of fatty acid alkyl esters or free fatty acids obtained by the steps of i) performing hydrolysis or alkyl esterification of a crude oil obtained from a microbial biomass from a microorganism capable of producing ARA or Mead acid to produce a hydrolyzed or esterified crude oil;
• and ii) purifying the hydrolyzed or esterified crude oil by rectification using a distillation column containing a structured packing, under conditions including a column bottom temperature of 160° C. to 230° C. and a minimum pressure in a distillation column of 0.1 Pa to 30 Pa,
• wherein the one or more trans isomers of ARA or Mead acid are generated during the rectification step as thermally-produced fatty acids.