Penicillin Acylase‐Catalyzed Solid‐State Ampicillin Synthesis

The ability of immobilized penicillin acylase from E. coli to retain a remarkable catalytic activity in solid‐state systems has been demonstrated. Stabilization of immobilized penicillin acylase by inorganic salt hydrates allowed us to exploit nearly the whole catalytic activity of the enzyme at a very low water content. Using this technique, enzymatic synthesis of ampicillin in solid‐state systems was performed with high yields (up to 70% starting from equimolar mixture of reagents) and rates comparable to the corresponding values in homogeneous solutions and heterogeneous systems, “aqueous solution‐precipitate”. Peculiarities of the enzymatic solid‐state acyl transfer process, such as absence of the clear‐cut maximum on the ampicillin accumulation curves and dependence of the synthetic efficiency on the enzyme loading, have been observed. The space‐time yield of solid‐state enzymatic ampicillin synthesis was shown to be up to ten times higher compared to the homogeneous solutions and heterogeneous “aqueous solution‐precipitate” systems.