Preparation of microbial oil

Abstract

The present invention provides a process for the production of a microbial oil comprising culturing a micro-organism in a two stage fermentation process where, in a last stage that precedes the end of fermentation, the carbon source is: consumed by the micro-organisms at a rate greater than it is added to the medium; added at a rate #0.30 M carbon/kg medium; or is rate limiting on the growth of the micro-organism. The micro-organisms thus have the carbon source restricted so that they preferentially metabolise fats or lipids other than arachidonic acid (ARA), so increasing the proportion of ARA in the cells. A microbial oil is then recovered from the micro-organism, using hexane as a solvent, that has at least 50% ARA and at least 90% triglycerides.

1 . A process for the production of a polyunsaturated fatty acid (PUFA), the process comprising culturing a micro-organism in a culture medium inside a fermentation vessel, whereby at a stage which precedes the end of fermentation;
 a) the carbon source is consumed by the micro-organisms at a rate greater than it is added to the medium;   b) the carbon source is added at a rate of # 0.30M carbon/kg medium per hour;   c) the carbon source is rate limiting on the growth of the micro-organisms, or is restricted such that the micro-organisms metabolise fat(s) and/or lipid(s);   d) the rate of addition of the carbon source is reduced or is below the rate of consumption of the carbon source by the micro-organisms; or   e) the carbon source has been all used, or has a concentration in the medium of about zero, at or before the end of fermentation;   f) the carbon source addition is stopped but fermentation is allowed to continue; and/or   g) the micro-organisms are subjected to conditions whereby they metabolise, or consume, one or more fat(s) or lipids(s) in preference to arachidonic acid (ARA).   
   
   
       2 . A process according to  claim 1 , wherein:
 h) the concentration of the carbon source in that stage is on average # 10 g/kg and/or # 0.17 M carbon/kg medium;   i) the carbon source is glucose; and/or   j) the PUFA is present in a microbial oil.   
   
   
       3 . A process according to  claim 2 , wherein:
 k) the second stage starts at from 15 to 2 hours before the end of the fermentation or less than 10 days after the beginning of the fermentation.   
   
   
       4 . A process according to  claim 3 , wherein:
 l) the (entire) fermentation is carried out at a temperature ∃22° C. or and/or <30° C.;   m) it is conducted in the absence of an additive oil; and/or   n) the fermentation lasts no longer than 9 days.   
   
   
       5 . A process according to  claim 4 , wherein:
 n) the PUFA comprises arachidonic acid (ARA); and/or   o) the vessel has a capacity of at least 10 litres.   
   
   
       6 . A process according to  claim 1  wherein the micro-organism is  Mortierella , optionally  Mortierella alpina , and/or is non-genetically modified. 
   
   
       7 . A microbial oil which comprises at least 50% arachidonic acid (ARA) and:
 a) has at least a 90% triglyceride content;   b) has a peroxide value (POV) of no more than 2.5;   c) has an anisidine value (AnV) of no more than 1.0;   d) is hexane extracted; and/or   e) has a phospholipid content below 5%.   
   
   
       8 . An oil according to  claim 7  which comprises:
 f) less than 5% of C 20  and/or C 24  polyunsaturated fatty acids (PUFAs); and/or   g) less than 5% of C 22+  PUFAs.   
   
   
       9 . An oil according to  claim 8  wherein:
 h) the free fatty acid content is ≦0.4%;   i) the triglyceride content is at least 95% or 98%.   
   
   
       10 . A composition comprising a microbial oil obtainable by a process according to  claim 1 . 
   
   
       11 . A composition according to  claim 12  which is a foodstuff, food, feed, or feed supplement, pharmaceutical, veterinary or cosmetic composition. 
   
   
       12 . A composition comprising a microbial oil of  claim 7 . 
   
   
       13 . An infant formula composition comprising a composition according to  claim 12 .