GROWTH OF NONPROTEOLYTIC LACTOCOCCUS-LACTIS IN CULTURE-MEDIUM SUPPLEMENTED WITH DIFFERENT CASEIN HYDROLYZATES

The growth and lactic acid production of nonproteolytic variants of La ctococcus lactis, three Lactococcus lactis ssp. cremoris strains (E8, Wg2, and HP) and one Lactococcus lactis ssp. lactis strain (1076), wer e compared with those of their parent strains in Garches medium supple mented with different casein hydrolyzates. Molecular weight distributi on and AA composition of casein hydrolyzates were different. Two fract ions of alcalase casein hydrolyzates separated and concentrated by a t wo-step ultrafiltration process were compared with two commercial case in hydrolyzates. Proteinase-negative variants of lactococci exhibited the same specific growth rate and production of lactic acid as protein ase-positive strains in all enriched Garches media. Cell growth was af fected by molecular weight distribution of peptides in hydrolyzates, b ut not by their AA composition. Lactococcus lactis ssp. lactis grew be tter than L. lactis ssp. cremoris, but its lactic acid production was similar to that of E8 strains. Among L. lactis ssp. cremoris, Wg2 stra ins grew better in Garches medium supplemented with casein hydrolyzate s with molecular weight <2000 Da, but growth and lactic acid productio n of HP strains were better in Garches medium enriched with casein hyd rolyzates with molecular weight >2000 Da. Different casein hydrolyzate fractions could be used to supplement culture medium and to standardi ze milk cultures; however, choice of casein hydrolyzates depends on su bspecies of lactococci.