| 摘要 |
An enzyme, called diacetyl reductase, can be used to produce acetoin from diacetyl and can be isolated from Lactobacillus kefir, L. plantarum, L. brevis, L. buchneri; from Leuconostoc cremoris, Candida boidinii, Hansenula polymorpha, Kluyveromyces lactis or Torulopsis candida. Particularly expedient in this connection is a diacetyl reductase which is able to reduce diacetyl selectively to (+)-acetoin and can be obtained from one of the abovementioned Lactobacillus strains. Two reductases (E1 and E2) which are capable of enantiomer formation and demonstrably have molecular weights of 66,000 +/- 5,000 and 74,000 +/- 5,000 have been highly purified, and it has been found that the pH optimum for the reduction reaction is 5 +/- 1; the temperature optimum is 70 DEG C; and the residual activity after storage at 6 DEG C and a pH between 5 and 10 for one week is 60%. There is furthermore substrate specificity for diacetyl, pyruvate and pyruvate ethyl ester besides other diketones such as acetylacetone, phenylpyruvate, diacetylbenzene and hexanedione. …<IMAGE>… |
