Simple enzymatic procedure for L-carnosine synthesis: whole-cell biocatalysis and efficient biocatalyst recycling.
Bottom Line: β-Peptides and their derivates are usually stable to proteolysis and have an increased half-life compared with α-peptides.Long-time as well as biocatalyst recycling experiments indicated a high stability of the developed biocatalyst for at least five repeated batches.Application of the recombinant E. coli in a fed-batch process enabled the accumulation of l-carnosine to a concentration of 3.7 g l(-1).
Affiliation: Laboratory of Chemical Biotechnology, TU Dortmund, 44221 Dortmund, Germany.Show MeSH
Related in: MedlinePlus
Mentions: The effect of pH on the formation of l‐carnosine and peptidic by‐products was studied in the range of pH 8–12 (Fig. 3). The pH value of the reaction system affected the yield of l‐carnosine and peptidic by‐products significantly. While maximal hydrolytic activities of DmpA were found to be between pH 8 and 9, l‐carnosine formation was most effective at pH 10. The corresponding maximal yield was 22.5% at this condition. The increase in yield on l‐carnosine in correlation to the pH is caused by the fact that deprotonated l‐histidine acts as effective nucleophile in the formation of peptide bonds, which was clearly observed at a pH value higher than pH 9. pH values higher than 11, however, reduced peptide formation significantly, most likely due to inactivation of the enzyme DmpA, or decreased stability of the amide. Additionally, the formation of the by‐products H‐β‐Ala‐β‐Ala‐His‐OH and H‐β‐Ala‐β‐Ala‐β‐Ala‐NH2 was also observed under all conditions. The highest yield of total peptide synthesis (l‐carnosine, H‐β‐Ala‐β‐Ala‐NH2, H‐β‐Ala‐β‐Ala‐β‐Ala‐NH2, H‐β‐Ala‐β‐Ala‐OH and H‐β‐Ala‐β‐Ala‐His‐OH) was 49% of the consumed H‐β‐Ala‐NH2 at pH 10 and 11. The remaining 51% were assumed to be the product of direct substrate hydrolysis, H‐β‐Ala‐OH. Consequently, pH 10 was used throughout the present study resulting in the highest l‐carnosine yield.
Affiliation: Laboratory of Chemical Biotechnology, TU Dortmund, 44221 Dortmund, Germany.