Production of l -Glutamine by a Penicillin-Resistant Mutant of Flavobacterium rigense

Abstract

To establish a practical method for the fermentative production of l -glutamine, cultural conditions for the accumulation of a large amounts of l -glutamine were investigated by using Flavobacterium rigense 703, which was previously reported by us as a l -glutamine-producing mutant. As a result, a yield of 25 mg of l -glutamine per ml was obtained after a 48-h cultivation in a medium containing glucose, yeast extract, (NH 4 ) 2 -fumarate, KH 2 PO 4 , K 2 HPO 4 , MgSO 4 .7H 2 O, and CaCO 3 (pH 6.4). Accumulation of l -glutamine was dependent upon the concentration of (NH 4 ) 2 -fumarate, and a suboptimum growth at a relatively high concentration of (NH 4 ) 2 -fumarate was essential for the maximum production of l -glutamine. At the optimum conditions, glutamic acid was formed as a by-product at a concentration of less than 1 mg/ml, but accumulation of the other amino acids was negligible. The product was isolated from the culture broth and readily purified by anion-exchange chromatography. The pure crystals of l -glutamine obtained in an 80% yield were optically and chromatographically pure.