Carob extract is known to be utilized by using fermentation methods. Lactic acid is considered to be one of the most useful chemicals, used in food, textile and pharmaceutical industries. Lactic acid consumption has recently increased because of its role as a monomer in the production of biodegradable polylactic acid (PLA), which is known as a sustainable bioplastic material. Overall, this study was undertaken to evaluate the potential of carob extract for lactic acid production. Although carob pod contains 40-50% sugars (especially, sucrose), L. casei could not metabolize them in this complex form. Therefore, sucrose in extract was converted into the monosaccharides by using invertase enzyme before fermentation. The maximum lactic acid concentration and yield for carob extract with yeast extract was 31.02 (g/L) and 54.06% compared with 62.37 (g/L) and 69.20% which was the maximum lactic acid concentration and yield for carob extract bu using invertase enzyme before fermentation. Results showed that carob pods can be a good feedstock for lactic acid production by L.casei.