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
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Mentions: In the next step, stability of the biocatalyst was tested in sequential batch experiments. Synthesis was conducted in 50 ml reaction volumes operated in a sequence of five repeated batches. After every batch, cells were harvested by centrifugation and re‐suspended in the same volume of fresh reaction buffer. The time‐courses of the five repeated batches for l‐carnosine synthesis are presented in Fig. 7. Substrate conversion and productivities increased significantly from the third batch onwards. Rather constant activities were found for the first three batches of 2.02, 2.06 and 2.08 mmol l−1 h−1, respectively, whereas a significant increase was observed for the fourth (2.23 mmol l−1 h−1) and fifth (2.37 mmol l−1 h−1) batch. The increase of activity strongly underlines the argumentation of membrane permeabilization. Besides, it is apparent that loss of enzyme activity did not occur in our experiments and thus the presented biocatalytic system offers a stable system and promising route for l‐carnosine synthesis.
Affiliation: Laboratory of Chemical Biotechnology, TU Dortmund, 44221 Dortmund, Germany.