Abstract:

To investigate the effect of exogenous addition of Vitamin B12 (VB₁₂) on the production of 3-hydroxypropionic acid (3-HP) through glycerol reduction pathway in Klebsiella pneumoniae HD79 and K. pneumoniae HD79-T, and to explore the threshold upper limit of VB₁₂ on the above strains, different concentrations (0.01, 0.02, 0.03, 0.04, and 0.05 g/L) of VB₁₂ were added to the fermentation medium of K. pneumoniae HD79 and K. pneumoniae HD79-T. The consumption of substrates and production of products were detected by HPLC, mRNA expression of genes related to the reduction pathway was detected by qRT-PCR, and enzyme activities related to metabolism were detected by enzyme-linked immunosorbent assay (ELISA). The results showed that the thresholds of VB₁₂ for K. pneumoniae HD79 and K. pneumoniae HD79-T was 0.01 g/L and 0.03 g/L, respectively. Compared with the absence of VB₁₂, the productions of 3-HP of K. pneumoniae HD79 and K. pneumoniae HD79-T were increased by 24.39% and 8.86%, respectively; the expression levels of aldehyde dehydrogenase gene puuC were increased by 2.49-fold and 1.68-fold, respectively; the enzyme activities of ALDH, GDHt, and PDOR increased by 50.24%, 40.36%, and 18.29% in K. pneumoniaeHD79, and by 30.49%, 37.84%, and 13.56% in K. pneumoniae HD79-T, respectively. These results indicated that exogenous addition of coenzyme factor VB₁₂ was a feasible strategy for high production of 3-HP in Klebsiella pneumoniae.

Key words: Vitamin B₁₂, Klebsiella pneumoniae, 3-hydroxypropionic acid, aldehyde dehydrogenase gene puuC, glycerol dehydratase