Improvement of Riboflavin Production by Lactobacillus fermentum Isolated from Yogurt

Abstract

The riboflavin production by Lactobacillus fermentum isolated from yogurt was improved by inactivation of folE gene. Guanosine triphosphate (GTP) serves as the precursor for both folate as well as riboflavin biosynthesis. The folE gene of Lb. fermentum, which codes for GTP cyclohydrolase I was inactivated by the insertion of erythromycin resistance gene cassette through recombination and the riboflavin production by the parental and mutant strains were estimated. Inactivation of the folE gene involved in folate biosynthesis pathway resulted in enhanced level of riboflavin production by Lb. fermentum, since more amount of GTP molecules are made available for the GTP cyclohydrolase II mediated riboflavin biosynthesis pathway. In a chemically defined medium, the Lb. fermentum produced 2.29 mg L⁻¹ of riboflavin at 24 h of fermentation. Whereas the folE disrupted mutant Lb. fermentum GKJFE produced approximately 50% more riboflavin (3.49 mg L⁻¹) than that of the parental strain at 72 h of fermentation.

Keywords:

• folate
• gene disruption
• GTP cyclohydrolase I
• Lactobacillus
• riboflavin

ACKNOWLEDGMENTS

The authors thank the Directorate of Extramural Research and Intellectual Property Rights, Defense Research Development Organization (DRDO), for financial support (No.ERIP/ER/0503551/M/01/921). We thank Dr. J. Gowrishankar, Director, CDFD, Hyderabad, for kindly providing the vector pULP8. SJ thanks UGC-NRCBS, Madurai Kamaraj University, for providing the visiting fellowship.