Diacetyl
Mostrando 13-24 de 117 artigos, teses e dissertações.
-
13. Atividade antimicobacteriana, citotoxicidade e interaÃÃo com macrÃfagos J774 de lipossomas contendo Ãcido Ãsnico
Secondary lichen metabolite usnic acid (UA) [2,6-diacetyl-7,9-dihydroxy-8,9b-dimethyl-1,3(2H,9bH)-dibenzofurano] is known by its antimicrobial activity against gram-positive bacteria and mycobacteria. Pulmonary tuberculosis is characterized by involvement of macrophages containing inside a large number of Mycobacterium tuberculosis. Liposomes have long been
Publicado em: 2006
-
14. Structural Studies of 2,6-Diacetyl- and 2,6-Diformylpyridine Bis(thiosemicarbazones)
Embora um grande número de estruturas tiosemicarbazonas heterocíclicas tenham aparecido na literatura recentemente, poucas estruturas de bis(tiosemicarbazonas) heterocíclicas e dos seus complexos metálicos foram descritas. Complexos de ferro (II), índio (II), estanho (IV) e bismuto (III) contêm bis(tiosemicarbazonas) coordenadas na forma de ligantes pe
Journal of the Brazilian Chemical Society. Publicado em: 2002-02
-
15. Enzymatic Removal of Diacetyl from Beer: II. Further Studies on the Use of Diacetyl Reductase1
Diacetyl removal from beer was studied with whole cells and crude enzyme extracts of yeasts and bacteria. Cells of Streptococcus diacetilactis 18-16 destroyed diacetyl in solutions at a rate almost equal to that achieved by the addition of whole yeast cells. Yeast cells impregnated in a diatomaceous earth filter bed removed all diacetyl from solutions percol
-
16. Diacetyl and Acetoin Production by Lactobacillus casei
Agitation of broth cultures of Lactobacillus casei retarded cellular dry weight accumulation but enhanced production of both diacetyl and acetoin. Addition of pyruvate overcame this retardation, but addition of sulfhydryl-protecting reagents did not. Both pyruvate and citrate enhanced accumulated dry weight of L. casei incubated without agitation, but only p
-
17. 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,
-
18. Differences between Lactobacillus casei subsp. casei 2206 and Citrate-Positive Lactococcus lactis subsp. lactis 3022 in the Characteristics of Diacetyl Production
Lactobacillus casei subsp. casei 2206 exhibited much lower levels of diacetyl reductase activity than Citr+Lactococcus lactis subsp. lactis 3022 but two-, three-, and more than eightfold-higher levels of diacetyl synthase, lactate dehydrogenase, and NADH oxidase activities, respectively. A requirement for metal ions by the diacetyl synthases in both species
-
19. Incorporation of Radioactive Acetate into Diacetyl by Streptococcus diacetilactis
Streptococcus diacetilactis was grown in a partially defined, lipoic acid-free medium containing radioactive acetate with and without addition of 0.1% unlabeled sodium pyruvate. Labeled carbon was incorporated into diacetyl, but neither the amount of diacetyl produced nor its specific activity was influenced by addition of pyruvate. Acetoin had low specific
-
20. Detection of diacetyl (caramel odor) in presumptive identification of the "Streptococcus milleri" group.
The caramel odor associated with the "Streptococcus milleri" group was shown to be attributable to the formation of the metabolite diacetyl. Levels of diacetyl in the 22- to 200-mg/liter range were produced by 68 strains of the "S. milleri" group; apart from one strain of Streptococcus mutans, all 92 other strains of streptococci belonging to 12 species prod
-
21. Analysis of acetoin and diacetyl in bacterial culture supernatants by gas-liquid chromatography.
The acetoin and diacetyl contents of culture supernatants of Voges-Proskauer-positive "viridans" streptotocci, Klebsiella pneumoniae and Staphylococcus aureus, were determined by a gas liquid chromatographic procedure, in which supernatants were extracted with diethyl ether and diacetyl was measured on columns of 10% (wt/wt) polyethylene glycol 400 (PEG 400)
-
22. Acetoin Fermentation by Citrate-Positive Lactococcus lactis subsp. lactis 3022 Grown Aerobically in the Presence of Hemin or Cu2+
Citr+Lactococcus lactis subsp. lactis 3022 produced more biomass and converted most of the glucose substrate to diacetyl and acetoin when grown aerobically with hemin and Cu2+. The activity of diacetyl synthase was greatly stimulated by the addition of hemin or Cu2+, and the activity of NAD-dependent diacetyl reductase was very high. Hemin did not affect the
-
23. Genetic manipulation of the pathway for diacetyl metabolism in Lactococcus lactis.
Diacetyl is an important food flavor compound produced by certain strains of citrate-metabolizing lactic acid bacteria. Citrate is converted to pyruvate, from which diacetyl is produced via intermediate alpha-acetolactate. This paper reports the cloning and analysis of the gene (aldB) encoding alpha-acetolactate decarboxylase from Lactococcus lactis MG1363.
-
24. 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 uncharg