Enhanced Lactic Acid Production from Carob Extract by Lactobacillus casei Using Invertase Pretreatment

Abstract

Carob has been widely grown in the Mediterranean region for centuries. It has been regarded as only a forest tree and has been neglected for other economical benefits. However, in recent years, it has gained attention for several applications. In this study, carob extract has been used as carbon source in fermentation. Lactic acid is considered to be an industrial chemical used in food, textile and pharmaceutical industries. Lactic acid demand has recently increased because of its role as a monomer in the production of biodegradable polylactic acid (PLA), which is known as a sustainable and degradable bioplastic material. Therefore, this study was undertaken to evaluate the potential of carob extract for lactic acid production. Based on our previous study, the optimum extraction conditions were used to obtain the carob extract with high sugar content. Then, obtained extract was utilized by Lactobacillus casei for production of lactic acid by using suspended-cell fermentation. 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 prior to fermentation. Also, in order to determine economical appropriate nitrogen sources, four different nitrogen sources were evaluated. The maximum lactic acid concentration and yield for carob extract with yeast extract was 31.35 (g/L) and 68.79% compared with 59.27 (g/L) and 66.70% after using invertase enzyme. Results clearly showed that carob pods can be a good feedstock for lactic acid production by L. casei.

Keywords:

• Lactobacillus casei
• lactic acid
• fermentation
• invertase
• value-added products

ACKNOWLEDGMENTS

This study was supported in part by the Pennsylvania Agricultural Experiment Station, and The Akdeniz University Research Foundation. The authors gratefully acknowledge Yenigun Food, Inc. (Antalya, Turkey) and Griffin Industries, Inc. (Butler, Ky., USA) for supplying carob pods and alternative nitrogen sources, respectively.