title: Enhancement of riboflavin production by overexpression of acetolactate synthase in a pta mutant of Bacillus subtilis.
abstract: Genetic alterations of carbon flux into the acetoin biosynthesis pathway as a possible means to reduce acid accumulation were investigated in the riboflavin-producing Bacillus subtilis during growth on glucose. The lower rates of cell growth and riboflavin production were found in the pta-disrupted mutant while the rate of acetate formation was reduced. In contrast, acid accumulation was significantly reduced, to one-fifth that of the parental strain RH33::[pRB63](n), and a 50% increase in the riboflavin yield was obtained when the expression of the gene encoding acetolactate synthase was increased in the pta-disrupted mutant. Metabolic analysis, together with enzyme activity assays, indicated that the tricarboxylic acid cycle fluxes are significantly increased in response to acetolactate synthase overexpression in pta-disrupted mutant. Moreover, the intracellular ATP-to-ADP ratio also increased 5.8-fold. The high concentration of ATP could explain the increased riboflavin production.
authors.affiliation: Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.
authors.forename: Yingbo
authors.initials: Y
authors.lastname: Zhu
authors.forename: Xun
authors.initials: X
authors.lastname: Chen
authors.forename: Tao
authors.initials: T
authors.lastname: Chen
authors.forename: Xueming
authors.initials: X
authors.lastname: Zhao
mesh_terms: D000095:Acetolactate Synthase / Q000235:genetics* / Q000378:metabolism; D001412:Bacillus subtilis / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008954:Models, Biological; D009154:Mutation; D012256:Riboflavin / Q000096:biosynthesis* / Q000378:metabolism
chemical_list: D000095:Acetolactate Synthase; D012256:Riboflavin