Cell growth and bacteriocin production of probiotic Lactobacillus strains in different media

Growth, metabolism, and bacteriocin production by seven Lactobacillus strains including five commercial probiotic strains were studied during fermentation in MRS medium and milk medium at constant pH 6.5. These strains were Lactobacillus acidophilus ACC, L. acidophilus 11313 801, L. casei Imunitas, L. casei YIT 9029, L. gasseri K7, L. johnsonii La I, and L. rhamnosus GG. Although the L. casei complex strains grew to higher cell levels than the L. acidophilus complex strains in MRS medium, monitored bacteriocin titres were higher for the L. acidophilus complex strains. L. johnsonii Lai and L. gasseri K7 grew in milk medium only when yeast extract was added. Addition of yeast extract (0.3-1.0% w/v) to milk medium enhanced both growth and bacteriocin production for all strains. Bacteriocin production was clearly observed in yeast extract supplemented milk medium for L. acidophilus IBB 801, L. johnsonii Lai, and L. gasseri K7. L. acidophilus IBB 801, the only strain of dairy origin, displayed the best growth (10.5 log CFU mL(-1)) and bacteriocin production (3200 AU mL(-1)). These findings demonstrated that probiotic lactobacilli from an intestinal origin are difficult to cultivate in milk. (C) 2004 Elsevier Ltd. All rights reserved.