Recently, lactic acid bacteria LAB have attracted a great deal of interest because of their potential to serve as oral delivery vehicles for recombinant protein vaccines. An important limitation to their use is the typically low level of heterologous expression obtained in LAB. to address this, a dynamic flux balance analysis DFBA model was used to identify gene targets for increasing specific expression of Green Fluorescent Protein GFP, a model heterologous protein, in Lac to coccus lactis IL1403. Two strains, each targeting one of the top model-identified genes, were constructed and tested in vivo. Data show that both strains, by a conservative estimate, achieved 15% higher GFP per cell than the control strain, a qualitative confirmation of the model predictions. A genome-scale DFBA model for L. lactis growing on M17 medium is presented along with the procedure for screening gene targets and a powerful method for visualizing fluxes in genome-scale metabolic networks. C 2009 Elsevier Inc. All rights reserved.