Nisin-Z production was studied during repeated-cycle pH-controlled batch (RCB) cultures using Lactococcus lactis subsp. lactis biovar. diacetylactis UL719 immobilized in κ-carrageenan/locust bean gum gel beads in supplemented whey permeate. After an initial colonization of gel beads during the first two cycles, nisin-Z production in bulk medium and gel beads was very similar for 1-h and 2-h cycle RCB cultures. A very high nisin-Z production (8200IUmL - 1 ) was measured in the broth after the 1-h cycles, with a corresponding volumetric productivity of 5730IUmL - 1 h - 1 . This productivity is much higher than maximum nisin productivities reported in literature or maximum productivities obtained previously for free-cell batch cultures (850IUmL - 1 h - 1 ), and free-cell (460IUmL - 1 h - 1 ) or immobilized-cell (1760IUmL - 1 h - 1 ) continuous cultures, using the same strain and fermentation conditions. The stability of RCB cultures was demonstrated for 24 and 36 1-h cycles carried out over 3 and 6-day periods, respectively. Changing environmental conditions during batch cultures resulted high nisin production.