Efficient recovery of secretory recombinant proteins from protease negative mutant Escherichia coli strains

Osmotic shock and lysozyme/EDTA methods were used to recover secreted recombinant proteins from protease negative mutant strains of E. coli. Up to 80% of protein A-β-lactamase fusion protein was recovered from protease negative mutants by simple osmotic shock. Fractionation by lysozyme/EDTA treatment, increased the recovery of protein A-β-lactamase fusion protein from the mutant strain up to 93%. Mild fractionation condition allowed efficient recovery of secreted protein from protease negative mutant strains, but not from the parent strain possessing proteases.