The absence of carbon sources available for industrial microbial conversions, has triggered research oriented to the examination of non described, non tested agro-industrial by-products, for their potential utilization as carbon or nitrogen sources in specific fermentation processes. A collection of  Lactobacillus spp strains was screened with respect to their ability to grow on pectin and galacturonic acid as the only carbon source. Selected homofermentative strains were then evaluated for their productivity of lactic acid in complex media. Three strains, two of L. casei and one of L. rhamnosus, were used for testing different formulations of fermentation media, based on four different by-products of regional availability in Central Mexico: coffee mucilage, cane blackstrap molasses, rum vinasses and liquor from the alkaline cooking of corn. At present, all by-products are important pollutants and remain largely without treatment before disposal. Coffee mucilage is the viscous inner mesocarp of coffee cherry, and contains pectic substances, hemicelluloses, as well as fermentable sugars. Molasses and vinasses provided both readily fermentable carbon and nitrogen supplementation, whereas corn liquor is an excellent source of buffering salts. The best medium formulation, based both on performance and economy, allowed for the fermentation of more than 70% of the sugars, and an efficiency of 85% of lactic acid production based on fermented sugars.  Best performance was achieved when molasses and coffee mucilage were mixed (9:1), and dissolved in vinasses at different concentrations. Addition of alkaline corn liquor provided a feasible method for pH stabilization throughout the fermentation. Economical feasibility is analyzed.