Diacetyl reductase of Lactobacillus casei

Abstract

BRANEN, A. L., and T. W. KEENAN. 1970. Diacetyl reductase of Lnctobacilllts cnsei. Can. J. Microbial. 16: 947-951. Diacetyl reductase (diacety1:reduced nicotinamide adenine dinucleotide (NADH) oxidoreductase, EC. 1.1.1.5) has been isolated from Lactobacill~a casei. Cell sonication, ammonium sulfate fractionation, Sephadex gel filtration, DEAE-cellulose chromatography, and alumina gel adsorption were used to obtain the partially purified enzyme. Both NADH oxidase and diacetyl reductase activity were associated with the same fraction at all stages in purification. Growth in media containing added pyruvate resulted in a 10-fold increase in the NADH oxidase activity and a 3-fold increase in the diacetyl reductase activity of crude cell extracts on a protein basis. Purified preparations showed maximal reductase and oxidase activities at pH 4.5 and 5.0, respectively. Lineweaver-Burke plots yielded intersecting lines when NADH and diacetyl concentrations were varied, suggesting a flavin-linked reaction. The absorption spectrum of the purified preparation was characteristic of that of a flavoprotein. The product of the reduction of diacetyl was identified as acetoin. Acetoin and methylene blue were inactive as acceptors.

Transformation of Citric Acid to Acetic Acid, Acetoin and Diacetyl by Wine Making Lactic Acid Bacteria

“…Diacetyl reductase (Ee 1.1.1.5), which irreversibly converts diacetyl to acetoin, has been found in butter and milk lactic acid bacteria, Streptococcus species 36 ) and Lactobacillus casei. 37,38) Diacetyl reductase was also found in some strains of malolactic bacteria. The above results may suggest that a part of acetoin accumulated in malolactic fermented wines is formed by diacetyl reduction in addition to biosynthesis through o:-acetolactate from pyruvic acid.…”

Reconstruction and analysis of the genome-scale metabolic model of Lactobacillus casei LC2W

“…S1 in Supplementary file 1). In addition, 92 non-gene reactions (not counting exchange reactions) were added to the iJL846 model for modeling or by referring to the literature of L. casei; these reactions included the oxidative decarboxylation of α-acetolactate to diacetyl (Branen and Keenan, 1970) and the assembly of biomass macromolecules.…”

The effect of oxygen and pH on the glucose metabolism ofLactobacillus casei var.rhamnosus ATCC 7469

“…The joint presence of diacetyl and acetoin in these supernates is interesting as diacetyl reductase (E.C. 1.1.1.5) has been reported in a related strain (ATCC 393) of L. casei (Branen and Keenan, 1970). This enzyme is reduced NAD-dependent and it would seem likely that again, competition between this enzyme and the flavoprotein system for the reductant has partially incapacitated the reductase reaction thus leading to both diacetyl and acetoin being present simultaneously.…”

“…Although the oxidation ofpyruvate to acetate by a reduced NAD-independent mechanism has been established in L. delbrueckii (Hager, Geller and Lipmann, 1954), the absence of significant quantities of acetate in supernates would rule out this particular mechanism. Unpublished data of Branen and Keenan (see Branen and Keenan, 1970) indicate that L. casei ATCC 393 produces diacetyl from pyruvate. The present studies showed that diacetyl is produced only under conditions of aeration without pH control and even then less than 10~ of the glucose appeared as diacetyl.…”