Improved L-Threonine Production by the Amplification of the Gene Encoding Homoserine Dehydrogenase in Brevibacterium lactofermentum

Abstract

A 3.2 kb chromosomal DNA fragment encoding homoserine dehydrogenase (HD) of Brevibacterium lactofermentum M-15, a L-threonine and L-lysine producing mutant, was cloned into the unique Pstl site of vector plasmid pAJ1844. Strain M-15 was transformed with the obtained recombinant plasmid pAJ210. The transformant, AJ12021, showed 2-fold higher HD activity and accumulated a 1.4-fold higher amount of L-threonine (maximally 25.0 g/liter) than in the case of the host strain, M-15, respectively. The correlation between the amino acid production and the regulation of enzyme activities was discussed. © 1987, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.