title: Bio-transformation of Glycerol to 3-Hydroxypropionic Acid Using Resting Cells of Lactobacillus reuteri.
abstract: 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.
authors.affiliation: Centre for Biotechnology, Anna University, Chennai, Tamil Nadu, 600 025, India.
authors.forename: Gopi Gopal
authors.initials: GG
authors.lastname: Ramakrishnan
authors.forename: Ganesh
authors.initials: G
authors.lastname: Nehru
authors.forename: Pandiaraj
authors.initials: P
authors.lastname: Suppuram
authors.forename: Sowmiya
authors.initials: S
authors.lastname: Balasubramaniyam
authors.forename: Brajesh Raman
authors.initials: BR
authors.lastname: Gulab
authors.forename: Ramalingam
authors.initials: R
authors.lastname: Subramanian
mesh_terms: D001711:Biotransformation; D057465:Catabolite Repression; D025461:Feedback, Physiological; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D005990:Glycerol / Q000378:metabolism*; D019344:Lactic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D052200:Limosilactobacillus reuteri / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D011409:Propylene Glycols / Q000378:metabolism
chemical_list: D011409:Propylene Glycols; D009243:NAD; D019344:Lactic Acid; C041787:1,3-propanediol; C031601:hydracrylic acid; D005990:Glycerol