EFFECT OF CITRATE ON PRODUCTION OF DIACETYL AND ACETOIN BY LACTOCOCCUS-LACTIS SSP LACTIS CNRZ-483 CULTIVATED IN THE PRESENCE OF OXYGEN

The effect was studied of trisodium citrate addition on the growth and formation of diacetyl and acetoin by Lactococcus lactis ssp. lactis C NRZ 483 in a whey-based medium under an oxygen pressure of 2 atm. Grow th increased, as shown by the final absorbance of the culture, which w as 1.2 in the absence of citrate and 2.8 in the presence of 26 mM citr ate. In the absence of citrate, maximal concentrations of diacetyl and acetoin were 0.09 and 0.29 mM, respectively. When citrate was added a t 6.2, 11.5, and 26 mM, the maximal diacetyl concentrations were 0.45, 0.53, and 0.85 mM, and those of acetoin were 3.6, 4.5, and 8.5 mM, re spectively. However, under these conditions, the yield of citrate bioc onversion to diacetyl and acetoin decreased as the initial concentrati on of citrate increased. Yields were 121, 83, and 70% in the presence of 6.2, 11.5, and 26 mM citrate, respectively.