Obtaining lactic acid through microbial fermentation from corn residues

The production and kinetics of lactic acid (LA) by batch fermentation were studied, using corn residues as substrate with Lactobacillus delbrueckii spp. Bulgaricus. A factorial design was developed for the pretreatment stage of the residue and lactic fermentation to determine the best conditions for obtaining total reducing sugars and lactic acid. In the pretreatment, the best conditions were obtained by working with HCl at 3% (v/v), 75 °C, and 30 minutes of reaction. Fermentation was carried out, keeping the medium at a pH between 5.5-6, and the best working conditions were 100 µl of the microorganism, 37ºC, and 24 hours of fermentation, reaching a maximum concentration of 19.9 g/L. Kinetic models for LA production, bacterial growth, and substrate consumption were proposed. Likewise, to verify the observed data, different statistical indices were calculated to evaluate the accuracy of the models. Finally the Luedeking-Piret and logistic models, were selected as they presented the best fit to the experimental data for LA production, substrate consumption, and bacterial growth, respectively.