With the aim of producing L(+) and D(-) lactic acid to be employed in poly-lactic acid polymer production, for biomedical applications, the strains Lactobacillus casei subsp. casei DSM 20011 and Lactobacillus coryniformis subsp. torquens DSM 20004 were studied in a conventional chemostat mode using various dilution rates. The results obtained showed that the dilution rate influences the fermentation pattern, modifying various fermentation parameters. Nevertheless, the product and biomass yields remained constant and the ratio of the L(+) and D(-) isomers of lactic acid was not affected by the dilution rate. The optimal glucose concentration on inlet feed medium was also determined for the L. coryniformis fermentation.