FORMATION OF DIACETYL BY CELL-FREE-EXTRACTS OF LEUCONOSTOC LACTIS

Diacetyl formation was linear with time and with protein concentration when a cell-free extract of Leuconostoc lactis NCW1 was added to a bu ffer system containing pyruvate, thiamine pyrophosphate and MgSO4 (fin al concentrations 60 mM, 0.11 mM and 0.22 mM, respectively). No diacet yl was detected in the absence of pyruvate or cell-free extract and no increase in diacetyl formation was detected on the addition of acetyl -CoA. When 2-acetolactate (1.6 mM) was the substrate, autodecarboxylat ion to diacetyl and acetoin occurred under aerobic and anaerobic condi tions. When cell-free extract was added, decarboxylation of 2-acetolac tate to acetoin and diacetyl increased 4-6-fold, under aerobic and ana erobic conditions. When the cell-free extract was boiled, diacetyl for mation from 2-acetolactate was reduced to the level of autodecarboxyla tion. The results suggest that diacetyl is formed enzymatically in the presence and absence of oxygen, as well as spontaneously, from 2-acet olactate.