Process for extractive fermentation

A process for preparing a product selected from ethanol, penicillin, citric acid and polysaccharides by fermentation with a microorganism capable of producing said product and being selected from Saccharomyces cerevisiae or Zymomonas mobilis, Penicillium chrysogenum, Aspergillus niger and Pulularia pullulans respectively, which process comprises:

• continuously introducing an aqueous solution containing a substrate for the microorganism into a continuous stirred tank fermentor containing an aqueous fermentation medium and said microorganism in freely suspended form;
• continuously withdrawing said aqueous fermentation medium from the fermentor at a rate substantially equal to the rate of introduction of said substrate solution;
• continuously introducing a liquid into said fermentation to contact the fermentation medium, said liquid being an extractant for the product selected from the group consisting of (A) double bond unsaturated aliphatic alcohols having 12 or more carbon atoms;
• (B) saturated branched chain aliphatic alcohols having 14 or more carbon atoms or mixtures thereof;
• (C) double bond unsaturated aliphatic acids having 12 or more carbon atoms;
• (D) aliphatic and aromatic mono-, di- or tri-esters having 12 or more carbon atoms, other than dibutyl phthalate;
• (E) aliphatic noncyclic ketones and aliphatic aldehydes having 12 or more carbon atoms:
• and (F) mixtures of extractants from groups (A) to (E) above or mixtures of at least one of the above extractants and at least one other extractant;
• continuously withdrawing said liquid from the fermentor after said contact with the fermentation medium at a rate substantially equal to the rate of introduction of the liquid into the fermentator;
• and
• separating said product from the liquid withdrawn from the fermentor and recirculating the remaining liquid to the fermentor as at least part of the liquid being introduced therein.