Bioconversion Of Phenylpyruvic Acid To L-phenylalanine By Mixed-gel Immobilization Of Escherichia Coli Ep8-10

摘要

A mixed-gel of κ-carrageenan and gelatin was used in L-phenylalanine production. The mixed-gel, containing 87.5% κ-carrageenan and 12.5% gelatin [the total gel concentration was 4 wt%], showed the best performance and was selected for further study with Escherichia coli EP8-10. The optimum pH and temperature were 8.5 and 37 ℃, respectively. The effects of trehalose and Mg~(2+) were studied in the mixed-gel immobilization. Their optimum concentrations were 5 × 10~(-2) and 2 × 10~(-3) mol/L, respectively. Under the optimal conditions, 98.3% of the phenylpyruvic acid (PPA) was converted to L-phenylalanine. The activity recovery of the transaminase enzyme in the mixed-gel immobilization was higher than that in single K-carrageenan immobilization, which was 93.6%. The total PPA conversion rate was over 80% in all 15 batches, suggesting great sustainability in the mixed-gel immobilization. The maximum reaction rate (r_(max)) was calculated to be 4.75 × 10~(-2) mol/(Lgh).