title: Depression of by-product formation during L: -isoleucine production by a living-cell reaction process.
abstract: Two unnatural and unwanted amino acids, norvaline (Nva) and O-ethylhomoserine (O-EH) are formed as by-products in L: -isoleucine production by Brevibacterium flavum AB-07 using a new process named the living cell reaction process. Nva formation was depressed by using a leucine auxotrophic mutant (AB-07-Leu-2) derived from strain AB-07. It was found that Nva formation was closely related to leucine biosynthesis. O-EH formation was repressed by addition of L: -methionine to the reaction mixture. However, the homoserine-O-acetyltransferase of AB-07-Leu-2 was not subject to either inhibition or repression by addition of L: -methionine. Furthermore, the O-EH-forming enzyme, which converts O-acetylhomoserine to O-EH, was speculated to be repressed by L: -methionine.
authors.affiliation: Tsukuba Research Center, Mitsubishi Petrochemical Co., Ltd., 8-3-1 Chuo, Ami, 300-03, Inashiki, Ibaraki, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Terasawa
authors.forename: Masayuki
authors.initials: M
authors.lastname: Inui
authors.forename: Makoto
authors.initials: M
authors.lastname: Goto
authors.forename: Yasurou
authors.initials: Y
authors.lastname: Kurusu
authors.forename: Hideaki
authors.initials: H
authors.lastname: Yukawa