Improvement of Diacetyl Production by Lactococcus lactis ssp. lactis CNRZ 483 Through Oxygen Control

This study illustrated the effect of controlled oxygenation on diacetyl production by citrate-utilizing Lactococcus lactis ssp. lactis CNRZ 483. Effects of soluble oxygen concentrations a t 21 and 50% of the medium saturation and pressurization of the reactor under 1 and 2 atm (atmospheres) of oxygen were tested. Oxygen had a slightly negative effect on the growth of L. Zactis ssp. Zactis CNRZ 483. In contrast, oxygen had a substantial effect on diacetyl production. Under nitrogen, the maximal concentration of diacetyl in the medium was 0.015 mM; diacetyl maxima were 0.13 and 0.26 m M when soluble oxygen concentrations were 21 and 5096, respectively. Diacetyl production reached a maximum of 0.39 and 0.45 mM when oxygen pressures of the culture were 1 and 2 atm, respectively. The effect of oxygen on lactate dehydrogenase activity and on chemical decarboxylation of a-acetolactate explained the higher diacetyl production.