Bacteriocin production by Lactobacillus pentosus B96 can be expressed as a function of temperature and NaCl concentration

Lactobacillus pentosus B96 is a bacteriocin-producing strain that was isolated from fermenting olive brines. The aim of the present work was the optimization of bacteriocin production, using response surface methodology (RS). A two-level screening Plackett-Burman design was used to select influencing factors. Then, a central composite design, with three repetitions in the centre, for pH, NaCl concentration, and temperature was carried out. Finally, an RS, which included the region of maximum accumulated bioactivity, was built as a function of NaCl concentration and temperature. Bioactivity accumulation was always observed during the exponential growth-phase, although no apparent correlation between maximum accumulated bioactivity and biomass formation was found. L. pentosus B96 is known to grow better at about 30 degrees C, neutral pH, and by the absence of NaCl; however, a suboptimal temperature (22 degrees C) and a moderate NaCl stress (0.65 mol(-1)) stimulated bacteriocin production. The research led to environmental conditions that maximized bacteriocin activity, which can be expressed as a polynomial function of temperature and NaCl concentration. The suboptimal growth conditions, which were found to produce the highest bacteriocin titres, resembled those prevailing during green table olive fermentation. This model can be used to improve "in situ" bacteriocin production thus contributing to the microbiological control of the process. (c) 2005 Elsevier Ltd. All rights reserved.