KINETIC-BEHAVIOR OF LACTOCOCCUS-LACTIS SSP LACTIS BV DIACETYLACTIS IMMOBILIZED IN CALCIUM ALGINATE GEL BEADS

Alginate beads with entrapped Lactococcus lactis spp. lactis by. diace tylactis were used as biocatalysts in continuous fermentation and the dynamics of the system analysed. Colonization by cells changed during fermentation, concentrating at the periphery (where cell densities rea ch 350 g litre(-1)). In the steady state, colonization of the gel was interrupted while growth continued, producing cells that were released into the effluent medium. The initial cell concentration in the beads had little influence on steady-state gel activity, while bead radius (0.75 to 1.5 mm) modified growth and acid production. A higher growth yield and cell release rate were obtained with smaller beads. Activity inside beads was not limited by external transfer, but rather by inte rnal transfer and by the reaction. The increase of citrate concentrati on in the feeding medium activates citrate utilization, diacetyl + ace toin production, and leads to a great enhancement of citrate bioconver sion to aroma compounds.