Fermentative production of L-glutamine by sulfaguanidine resistant mutants derived from L-glutamate producing bacteria.

Abstract

Excellent L-glutamine producers were screened for among sulfaguanidine resistant mutants derived from the wild type L-glutamic acid-producing bacteria, Brevibacterium flavum, Brevibacterium lactofermentum, Corynebacterium glutamicum and Microbacterium ammoniaphilum. The best strain, No. 1-60, was a sulfaguanidine resistant mutant derived from B. flavum 2247 by mutation. Strain No. 1-60 accumulated 41.0mg/ml of L-glutamine after 48 hr of cultivation from 10% glucose as a carbon source. This yield was the highest among those so far reported. The addition of Mn2+ (2ppm) to the standard medium for B. flavum 2241 decreased the L-glutamine production and increased the L-glutamic acid excretion markedly. On the contrary, strain 1-60 was not affected the Mn2+ (2ppm) addition at all. Glutamate kinase activity and the intracellular content of ATP in sulfaguanidine resistant mutant No. 1-60 were higher than those in the parent strain, B. flavum 2247. It was confirmed that the increase in glutamate kinase and the increase in internal ATP, which were important for the L-glutamine synthesis, were very effective for the improvement of L-glutamine-producing mutants.