The aim of the present study was to show the effect of carbon-nitrogen ratio (C/N ratio) and initial pH culture medium on the production of biomass and L-(+)-lactic acid by Lactobacillus casei subsp casei NRRL-441. The response surface methodology implementing a Box-Behnken experimental design yields estimation of the optimal culture conditions (within the selected variables range). Lactose and yeast extract, casein peptone and meat extract were the carbon and nitrogen main sources. The maximum biomass (4.07gL-1) and lactic acid (27.56 gL-1) productions were obtained when initial pH was 7.5 and C/N ratio of 4.13. The kinetic reaction exerted under the optimal conditions was modeled using an aggregated Monod, Luedeking and Piret models, respectively. Such conditions yield to propose a modified culture medium with yeast extract (27 gL-1) as the nitrogen source and lactose (20 gL-1) as carbon source. The achieved optimal C/N ratio was fixed to 4.13. Yeast extract replaces casein peptone as well as meat extract with a positive effect on lactic acid production yielding a concentration of 30.06 gL-1. A novel parametric identification method yields the characterization of the lactic acid production under the selected experimental conditions. The estimated model correlates with experimental data with enough accuracy.

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