IMPROVEMENT OF DIACETYL PRODUCTION BY LACTOCOCCUS-LACTIS SSP LACTIS CNRZ-483 THROUGH OXYGEN CONTROL

This study illustrated the effect of controlled oxygenation on diacety l production by citrate-utilizing Lactococcus Lactis ssp. Lactis CNRZ 483. Effects of soluble oxygen concentrations at 21 and 50% of the med ium saturation and pressurization of the reactor under 1 and 2 atm (at mospheres) of oxygen were tested. Oxygen had a slightly negative effec t on the growth of L. lactis ssp. lactis 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 mM when soluble oxygen concentrations were 21 and 50%, respectively. Diacetyl production reached a maximum of 0.3 9 and 0.45 mM when oxygen pressures of the culture were 1 and 2 atm, r espectively. The effect of oxygen on lactate dehydrogenase activity an d on chemical decarboxylation of ol-acetolactate explained the higher diacetyl production.