Glutamic acid production in biotin-rich media by temperature-sensitive mutants of Brevibacterium lactofermentum, a novel fermentation process.

Abstract

Temperature-sensitive mutants were derived from Brevibacterium lactofermentum strain 2256 in a search for mutants which would produce a large amount of L-glutamic acid in biotinrich media at the nonpermissive temperature. A total of 159 mutant strains was selected which showed adequate growth at 30°C but showed little or no growth at 37°C on minimal medium. Twenty of these were found to produce glutamic acid in a biotin-rich medium after a temperature shift from 30°C to 37°C, while the wild-type strain 2256 did not produce it under the same cultural condition. One of the typical mutant strains, Ts-88, produced approximately 2g/dl of glutamic acid from beet molasses (the yield>55%) in the presence of 33 μg/liter of biotin when temperature was shifted from 30°C to 40°C during the cultivation. It was concluded that, by controlling only temperature during fermentation, glutamic acid production could be realized in media containing biotin-rich natural carbon sources, without any chemical control such as the addition of expensive surface-active agents or antibiotics. Characteristics and merits of the novel fermentation process are discussed.