A green peptide synthesis—Using a magnetic biocatalyst in a stirred-tank bioreactor

The optimization of synthesis dipeptide derivative, N-Ac-Phe-Gly-NH2, catalyzed by immobilized α-chymotrypsin (α-chymotrypsin immobilized on Fe3O4-chitosan; α-chymotrypsin-Fe3O4-CS) in a stirred-tank bioreactor is evaluated by the experimental design. Three state-of-the-art green technologies (i.e., enzyme catalysis, immobilized enzyme, and magnetic bioreactor) are combined in this study. Response surface methodology (RSM) with a 3-factor-3-level Box-Behnken design is employed to evaluate the effects of the synthesis parameters, including reaction time (30–90 min), temperature (25–45 °C) and pH (7–9). A model for the synthesis is developed and the optimum conditions are predicted to be a reaction time of 92.3 min, a reaction temperature of 36.2 °C and pH 8.7. An experiment is performed under these optimum conditions and a yield of 82.26% is obtained. After the reaction, magnetically immobilized α-chymotrypsin is recovered by a magnetic field and used repeatedly to synthesize dipeptide at the optimum conditions. A yield of around 82% of dipeptide is obtained in the first 3 repeated batches and the yield over 70% is retained after ten batches. It is expected that this approach has great potential in industry for the large-scale production of the dipeptide derivative.