Bio-transformation of Glycerol to 3-Hydroxypropionic Acid Using Resting Cells of Lactobacillus reuteri

• Published in: Current microbiology Vol. 71; no. 4; pp. 517 - 523
• Main Authors: Gopal Ramakrishnan, Gopi, Nehru, Ganesh, Suppuram, Pandiaraj, Balasubramaniyam, Sowmiya, Raman Gulab, Brajesh, Subramanian, Ramalingam
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-10-2015; Springer Nature B.V
• Subjects: Biocatalysts; Biomass; Biomedical and Life Sciences; Biotechnology; Biotransformation; Catabolite Repression; Catalysis; Feedback, Physiological; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Glycerol; Glycerol - metabolism; Lactic Acid - analogs & derivatives; Lactic Acid - metabolism; Lactobacillus reuteri; Lactobacillus reuteri - metabolism; Life Sciences; Microbiology; Mutation; NAD - metabolism; Propylene Glycols - metabolism; Lactobacillus Reuteri; Catabolite Repression; Maximum Specific Productivity; Rhodococcus Erythropolis; NADH Ratio
• ISSN: 0343-8651; 1432-0991
• DOI: 10.1007/s00284-015-0878-7

Lactobacillus reuteri grown in MRS broth containing 20 mM glycerol exhibits 3.7-fold up-regulation of 3-hydroxypropionic acid (3-HP) pathway genes during the stationary phase. Concomitantly, the resting cells prepared from stationary phase show enhancement in bio-conversion of glycerol, and the maximum specific productivity (q ₚ) is found to be 0.17 g 3-HP per g CDW per hour. The regulatory elements such as catabolite repression site in the up-stream of 3-HP pathway genes are presumed for the augmentation of glycerol bio-conversion selectively in stationary phase. However, in the repression mutant, the maximum q ₚ of 3-HP persisted in the stationary phase-derived resting cells indicating the role of further regulatory features. In the production stage, the external 3-HP concentration of 35 mM inhibits 3-HP synthesis. In addition, it has also moderated 1,3-propanediol formation, as it is a redox bio-catalysis involving NAD⁺/NADH ratio of 6.5. Repeated batch bio-transformation has been used to overcome product inhibition, and the total yield (Ypx) of 3-HP from the stationary phase-derived biomass is 3.3 times higher than that from the non-repeated mode. With the use of appropriate gene expression condition and repeated transfer of biomass, 3-HP produced in this study can be used for low-volume, high-value applications.