Use of a D-optimal mixture design to estimate the effects of diverse chloride salts on the growth parameters of Lactobacillus pentosus

摘要

The effects of NaCl, KCl, CaCl_2, and MgCl_2 and their mixtures on the ionic strength (IS) of the medium and the growth parameters of Lactobacillus pentosus were studied by means of a D-optimal mixture experimental design with constrains (total salt concentration ≤ 9.0%, wt/vol) and the generalized z-value. The IS was linearly related to the concentrations of the diverse salts and its increase, for similar concentrations of salts, followed the order MgCl_2 > CaCl_2 > NaCl > KCl. Within the experimental region, the lag phase duration (λ) was mainly affected by NaCl and CaCl_2 and the interaction KCl with MgCl_2. The maximum specific growth rate (μ_(max)) decreased as NaCl (the highest effect), CaCl2, and MgCl_2 increased (regardless of the presence or not of previous NaCl); low KCI concentrations had a stimulating effect on μ_(max), but its overall effect showed a similar trend to the other salts. The maximum population reached (N_(max)) was the least affected parameter and decreased as NaCl and CaCl_2 concentrations increased regardless of the presence of the other salts. The equations that expressed the growth parameters as a function of the diverse chloride salts, within the limits assayed, were developed and the corresponding z- and harmonic Z-values were estimated.