Screening and characterization of protein-hyperproducing bacteria without detectable exoprotease activity.

Abstract

As the result of extensive screening, we isolated 37 protein-hyperproducing bacteria. Their protein productivities were highly stimulated by polypepton, but not by yeast extract or meat extract. These bacteria produced 4.5-11.5g/l of cell bound and extracellular proteins under appropriate cultural conditions. Many of the selected bacteria showed characteristics of Bacillus brevis or species related to it as to cellular morphology and physiology. The bacteria which seemed to be B. brevis mostly accumulated one or two major high-molecular-weight protein species. Several strains were found to have excellent ability to produce proteins and showed no detectable extracellular protease activity. Such bacteria are expected to be potential hosts for the production of foreign proteins through recombinant DNA technology.