Reduction Of Diacetyl Research Articles

A Screening Method of Bacteriat Reduction of Diacetyl

A qualitative method for screening bacteria for diacetyl-reducing activity is reported. This method is based on the color reaction of diacetyl, acctioin, and 2,3 butylene-glycol with a-naphthol and creatine.

Purification and properties of a diacetyl reductase from Escherichia coli.

A reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent reductase with the ability to reduce diacetyl has been isolated from Escherichia coli and has been purified 800-fold to near homogeneity. The product of the reduction of diacetyl was shown to be acetoin. The enzyme proved to catalyze the oxidation of NADPH in the presence of both uncharged alpha- and beta-dicarbonyl compounds. Even monocarbonyl compounds showed slight activity with the enzyme. On the basis of its substrate specificity, it is suggested that the enzyme functions as a diacetyl reductase. In contrast to other diacetyl reductases, the one reported here is specific for NADPH and does not possess acetoin reductase activity. The pH optimum of this enzyme was found to be between 6 and 7. The maximal velocity for the NADPH-dependent reduction of diacetyl was determined to be 9.5 mumol per min per mg of protein and the K(m) values for diacetyl and NADPH were found to be 4.44 mM and 0.02 mM, respectively. The molecular weight was estimated by gel filtration on Sephadex G-100 to be approximately 10,000.

Pigeon liver diacetyl reductase: Purification and some properties

1. 1. Diacetyl reductase (Acetoin:NAD + oxidoreductase, EC 1.1.1.5) from pigeon liver has been purified about 400 fold by a method including aqueous extraction, acetone precipitation and Sephadex G-100 chromatography. 2. 2. The purified preparations catalyze the (for all practical purposes) irreversible reduction of diacetyl to acetoin, using as hydrogen donors either NADH or NADPH. One single enzyme is responsible for the NADH- and NADPH-dependent reactions. Thus, the enzyme is different from that described by entry EC 1.1.1.5 in Enzyme Nomenclature (1972). 3. 3. Pigeon liver diacetyl reductase is highly specific with respect to hydrogen acceptors: it does not reduce acetoin, monoketones or nonvicinal diketones. 4. 4. The pH profiles show one single broad peak in the range 5.6–6.2. At pH 6.1 and 0.2 mM NADH, the apparent K m for diacetyl has been estimated to be 3.5 mM. The enzyme does not require metallic activators for maximal activity. 5. 5. The molecular weight, as calculated by Sephadex gel filtration, was found to be about 110 000.

Diacetyl, acetoin, and acetaldehyde production by mixed-species lactic starter cultures.

Citrate utilization and acetoin, diacetyl, acetaldehyde, and lactic acid production in milk at 21 C by five different mixed-strain starters, containing Streptococcus diacetilactis (D type), Leuconostoc (B type), and S. diacetilactis and Leuconostoc (BD type), were measured. BD and D cultures utilized citrate more rapidly and produced more diacetyl, acetoin, and acetaldehyde than B types. All cultures produced much more acetoin than diacetyl, with the BD and D cultures producing four to five times larger amounts of acetoin than the B cultures. Reduction of diacetyl and acetoin toward the end of the normal incubation period was characteristic of BD and D cultures, whereas a similar reduction of acetaldehyde was characteristic of BD and especially of B cultures. Continued incubation of B cultures beyond 17 h also resulted in reduction of diacetyl and acetoin. Addition of citrate to the milk retarded diacetyl and acetoin reduction. Mn(2+) had no effect on diacetyl production by a BD culture but increased citrate utilization and, as a consequence, caused greater diacetyl destruction in one of the B cultures.

Diacetyl, Acetoin, and Acetaldehyde Production by Mixed-Species Lactic Starter Cultures

Citrate utilization and acetoin, diacetyl, acetaldehyde, and lactic acid production in milk at 21 C by five different mixed-strain starters, containing Streptococcus diacetilactis (D type), Leuconostoc (B type), and S. diacetilactis and Leuconostoc (BD type), were measured. BD and D cultures utilized citrate more rapidly and produced more diacetyl, acetoin, and acetaldehyde than B types. All cultures produced much more acetoin than diacetyl, with the BD and D cultures producing four to five times larger amounts of acetoin than the B cultures. Reduction of diacetyl and acetoin toward the end of the normal incubation period was characteristic of BD and D cultures, whereas a similar reduction of acetaldehyde was characteristic of BD and especially of B cultures. Continued incubation of B cultures beyond 17 h also resulted in reduction of diacetyl and acetoin. Addition of citrate to the milk retarded diacetyl and acetoin reduction. Mn(2+) had no effect on diacetyl production by a BD culture but increased citrate utilization and, as a consequence, caused greater diacetyl destruction in one of the B cultures.

The reduction of diacetyl and acetoin in Aerobacter aerogenes. Evidence for one enzyme catalyzing both reactions.

The reduction of diacetyl and acetoin has been shown to be catalyzed by one enzyme in Aerobacter aerogenes. The ratio of the two activities remains constant during purification into homogeneity, and the two activities appear in the same amount whne the growing cells ae exposed to acetate.

Diacetyl reductase of Lactobacillus casei.

Diacetyl reductase (diacetyl:reduced nicotinamide adenine dinucleotide (NADH) oxidoreductase, EC. 1.1.1.5) has been isolated from Lactobacillus 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.