Use of methicillin and ampicillin mixture as a selective pressure in the cultivation of recombinant E. coli

Abstract

Ampicillin was rapidly degraded by an extracellular beta-lactamase, and was therefore ineffective to isolate plasmid-harboring cells in the cultivation of recombinant E. coli for the production of thermostable D-hydantoinase. An effective way of preventing the degradation of ampicillin, methicillin was employed as a beta-lactamase inhibitor. A mixture of methicillin and ampicillin was observed to effectively function as a selective pressure, and consequently plasmid stability and enzyme productivity of recombinant E. coli were highly maintained.