Combined effects of pH, yeast extract, carbohydrates and di-ammonium hydrogen citrate on the biomass production and acidifying ability of a probiotic Lactobacillus plantarum strain, isolated from table olives, in a batch system

A four variables-five levels Central Composite Design (CCD) was developed to model the individual and interactive effects of carbohydrates (lactose or maltose), yeast extract, di-ammonium hydrogen citrate and pH on the biomass production (Abs(600 nm)), viable and cultivable cell number and acidifying ability of a probiotic strain of Lactobacillus plantarum, isolated from table olives Bella di Cerignola. pH values were modeled through a negative Gompertz equation, in order to obtain the parameter alpha (metabolic adaptation time). This value and the biomass were submitted to a stepwise procedure and second order polynomial equations were derived. The parameter alpha was affected by the initial pH and lactose; the effect of the maltose, however, was not significant. The biomass production increased with increasing of yeast extract, di-ammonium hydrogen citrate and maltose concentrations and was maximum at pH 6.0 and 20 g l(-1) of lactose.