Production of High Levels of DHA in Microalgae Using Modified Amounts of Chloride and Potassium

Abstract

Methods for production of highly unsaturated fatty acids by marine microorganisms, including the heterotrophic marine dinoflagellate Crypthecodinium , using low levels of chloride ion are disclosed. Specifically, methods of increasing production of highly unsaturated fatty acids by marine microorganisms while growing in low chloride media by manipulating sodium ion and potassium ion levels. The invention also relates to methods of production of highly unsaturated fatty acids by marine organisms at low pH levels, and includes methods for generation of low pH tolerant strains.

1 - 21 . (canceled) 
     
     
         22 . A method of producing docosahexaenoic acid (DHA), comprising:
 culturing a heterotrophic microalga of the class Dinophyceae in a culture medium, wherein the culture medium comprises:
 chloride ion at a concentration of less than or equal to 3 g/L; and 
 potassium ion at a concentration of greater than or equal to 0.45 g/L; and 
   recovering DHA-containing lipid from the microalga, wherein the microalga produces at least 0.04 g DHA per 10 9  cells.   
     
     
         23 . The method of  claim 22 , wherein the microalga is of the genus  Crypthecodinium.    
     
     
         24 . The method of  claim 22 , wherein the microalga is of the species  Crypthecodinium cohnii.    
     
     
         25 . The method of  claim 22 , wherein the concentration of chloride ion is less than or equal to 2 g/L. 
     
     
         26 . The method of  claim 22 , wherein the concentration of chloride ion is less than or equal to 1 g/L. 
     
     
         27 . The method of  claim 22 , wherein the concentration of chloride ion is less than or equal to 0.3 g/L. 
     
     
         28 . The method of  claim 22 , wherein the concentration of potassium ion is greater than or equal to 0.5 g/L. 
     
     
         29 . The method of  claim 22 , wherein the concentration of potassium ion is greater than or equal to 0.6 g/L. 
     
     
         30 . The method of  claim 22 , wherein the concentration of potassium ion is greater than or equal to 0.8 g/L. 
     
     
         31 . The method of  claim 22 , wherein the culture medium further comprises sodium ion at a concentration of 1 g/L to 8 g/L. 
     
     
         32 . The method of  claim 22 , wherein a source of potassium comprises potassium sulfate. 
     
     
         33 . The method of  claim 22 , wherein the microalga produces at least 0.10 g DHA per 10 9  cells. 
     
     
         34 . The method of  claim 22 , wherein the microalga produces at least 0.20 g DHA per 10 9  cells. 
     
     
         35 . The method of  claim 22 , wherein the culture medium further comprises sodium ion, wherein a ratio of sodium ion to potassium ion is less than or equal to 27:1. 
     
     
         36 . The method of  claim 34 , wherein a ratio of sodium ion to potassium ion is less than or equal to 15:1. 
     
     
         37 . The method of  claim 36 , wherein a ratio of sodium ion to potassium ion is less than or equal to 4:1. 
     
     
         38 . The method of  claim 22 , further comprising recovering DHA from the DHA-containing lipid. 
     
     
         39 . A biomass produced by the method of  claim 22 . 
     
     
         40 . A lipid extracted from the biomass of  claim 39 .