PRODUCTION OF LACTOCOCCUS-LACTIS BIOMASS BY IMMOBILIZED CELL TECHNOLOGY

Calcium alginate beads containing Lactococcus lactis cells were used for three batch fermentations of milk or a commercially available growth medium (Gold Complete, Nordica) with the aim of producing concentrated cultures. Repeated fermentations did not significantly increase bead CFU counts which were between 3.3-7.8 x 10(10) CFU/g. During the second and third fermentations, which lasted 6 h each, the bead populations decreased if the incubation was extended over 2 h. There was cell release from the beads. Fermentation media and fermentation time all had an effect on free cell counts, but none of these factors statistically interacted. Free cell counts were higher at the end of fermentations 2 and 3 than in the first fermentation and approximately 50% of the population was in the free state. Free cell counts were higher when the beads were incubated in Gold Complete than in milk. Although the total bacterial population of a standard free cell fermentation was always higher than those having immobilized cells, immobilized cell technology did enable the production of dense cultures.