Aims: To study the effects of temperature, NaCl and acid (HCl, citric, acetic and lactic) concentrations on the specific growth rate (mu), lag phase (lambda), and h(0) of Lactobacillus pentosus IGLAC01. Methods and Results: Response surface (RS) methodology (D-optimal design) was used with a dummy variable, to account for the different types of acids. The variable ranges were: 16-30 degrees C, 0-70 g l(-1) NaCl, and 0-5 g l(-1) acid (or 0-2.5 g l(-1) HCl). Time to detection from optical density data was used to deduce mu and lambda. The RS models for log(2)mu and log(2)lambda, according to acid types, were estimated and the effects of variables were quantified by their z-generalized values. A relationship between ln h(0) with temperature was also found. Conclusions: The mu of L. pentosus IGLAC01 can be doubled by increasing temperature by 10.3 degrees C or by decreasing NaCl by 48 g l(-1) (harmonic, averaged, z values, Z); citric was the least inhibitory acid (z(mu) = -96.2) and lactic the strongest (z(mu) = -5.7), according to their generalized z values, z. A twofold lambda increase was achieved from a decrease of 3.1 degrees C (HCl), or 4.27 degrees C (citric) or 36 g l(-1) NaCl increase (both acids) (expressed as z(lambda)); the same effect was obtained from a decrease of 4.37 degrees C, 54 g l(-1) NaCl increase, or 10 g l(-1) acetic or lactic acid additions (expressed as Z(lambda) values). Significance and Impact of the Study: Valuable information on the effects of environmental variables on the biological parameters of L. pentosus IGLAC01, which could be used for the optimization of olive, cucumber or other vegetable fermentations, is obtained.