The Lactobacillus acidophilus growth was investigated to rind the optimal concentrations of 2 nitrogen sources (thought to be in excess) and 2 organic acids. A Plackett and Burman experimental design was used allowing identification of the more important factors with very few experiments. In the studied range, all the factors had a linear effect and a great influence on the final viability. 20 g/L of each nitrogen sources, 3 g sodium-citrate/L and 5 g sodium acetate/L are necessary. pH, temperature and glucose had poor influence.