Influence of Nutritional Conditions on Production of l -Glutamine by Flavobacterium rigense

Abstract

The nutritional conditions for the production of l -glutamine by Flavobacterium rigense strain 703 were investigated. The optimum concentration of ammonia for achieving the highest yield of l -glutamine (25 mg/ml of broth) was relatively broad, from 0.9 to 1.6%, whereas fumaric acid had a narrow optimum range, near 5.5%. High concentration of inorganic ions such as chloride or sulfate ion clearly inhibited cell growth. Therefore, ammonium salts other than (NH 4 ) 2 -fumarate were unsuitable for the highest production. The optimum concentration of (NH 4 ) 2 -fumarate was 7%. To reduce the concentration of fumaric acid in the medium, many substances were evaluated as substitutes. The fumaric acid concentration required for highest l -glutamine yield could not be replaced by any one of the compounds tested. However, part of fumaric acid could be replaced with succinic acid and cupric ion; 4% (NH 4 ) 2 -fumarate plus 2.5% succinic acid or 5% (NH 4 ) 2 -fumarate plus 1 mM cupric ion produced results similar to 7% (NH 4 ) 2 -fumarate in the fermentation medium.