9-40: Production of Lactic Acid from Sucrose: Strain Selection, Fermentation and Kinetic Modeling

Lactic acid is an important product arising from the anaerobic fermentation of sugars. It is used in the pharmaceutical, cosmetic, chemical and food industries as well as for biodegradable polymers and green solvents production. In this work, were used several bacterial strains isolated from industrial alcoholic fermentation, for screening of the best strain to lactic acid production. After of the screening was realized the fermentation with sucrose for lactic acid production. The fermentation was realized in batch system under anaerobic conditions for 48 hours, at a temperature of 37^oC, a pH value of 4.5 and 15 g/L of sucrose. Aliquots of the fermented broth were collected every 90 min for determining lactic acid, sucrose, biomass, and byproducts concentration. The pH of the medium was adjusted with sodium hydroxide. A chromatographic system equipped with an Aminex HPX-87H column and an UV and RI detection system was used to analyze sucrose, lactic acid, and byproducts of the fermentative process. To biomass determination liquid samples were centrifuged at 3000 rpm for 15 min and the cell pellets were washed twice with water. The cell were resuspended and dried in the stove at  75⁰C and dry mass was weighed. A kinetic model has been developed for represented in batch fermentation to produce lactic acid by strains isolated from industrial alcoholic fermentation. The data obtained from the fermentation were used for determining the kinetic parameters. The developed model allows very good predictions for lactic acid production, growth biomass and sugar consumption compared to experimental data.