Continuous production of l-phenylalanine from phenylpyruvic acid and l-aspartic acid by immobilized recombinant Escherichia coli SW0209-52

A recombinant strain Escherichia coli SW0209-52 was immobilized with κ-carrageenan for the production of l-phenylalanine via phenylpyruvic acid (PPA) and l-aspartic acid (l-Asp). To enhance operational stability, the immobilized cells were treated with 0.05% (w/v) glutaraldehyde and the relative activity was 122.8% compared with that without treatment. The conversion yield could stay above 88% in 10 batch cycles, indicating the stability of the immobilized cells. Continuous l-phenylalanine production with PBR was studied under different feeding PPA concentrations (15–40 g/L) and residence time (2.2–10 h). Considering both conversion yield and volumetric productivity, studies on the operational stability of the reactor were conducted under the condition of 30 g/L PPA feeding concentration and 10 h residence time. The system could be operated for 40 days without significant decline and the average productivity was 1.85 g/L/h and the conversion yield was above 85% throughout the 40 days.