Enhanced conversion of L-lysine to L-pipecolic acid using a recombinant Escherichia coli containing lysine cyclodeaminase as whole-cell biocatalyst

L-pipecolic acid, a fundamental chiral unit for numerous alkaloids and drugs, was biosynthesized from L-lysine using recombinant Escherichia coli containing pipA as the whole-cell catalyst. The effects of pH, temperature, surfactant, NAD+, Fe2+ concentration and substrate and product concentration on L-pipecolic acid bioconversion were investigated in small scale experiments. By optimizing the reaction conditions, a dramatic increase (71.8%) in L-pipecolic acid concentration and yield was observed. Furthermore, whole-cell biocatalyst reaction process with repeated cell recycling to eliminate product inhibition was conducted in 1-L bioreactor under the optimum reaction conditions for L-pipecolic acid production. In the presence of NAD+, an average L-pipecolic acid concentration of 17.25 g/L was achieved with a productivity of 0.36 g/(L h) after three cycles of cell recycling, which was up to 2.7 fold higher, when compared with that obtained in the process without repeated cell recycling. Thus, this study suggests that whole-cell biocatalyst may be an alternative choice for simple and efficient L-pipecolic acid production.