We developed a new bacterial expression system that utilizes a combination of attributes (low temperature, induction of an mRNA-specific endoribonuclease causing host cell growth arrest, and culture condensation) to facilitate stable, high level protein expression, almost 30% of total cellular protein, without background protein synthesis. With the use of an optimized vector, exponentially growing cultures could be condensed 40-fold without affecting protein yields, which lowered sample labeling costs to a few percent of the cost of a typical labeling experiment. Because the host cells were completely growth-arrested, toxic amino acids such as selenomethionine and fluorophenylalanine were efficiently incorporated into recombinant proteins in the absence of cytotoxicity. Therefore, this expression system using Escherichia coli as a bioreactor is especially well suited to structural genomics, large-scale protein expressions, and the production of cytotoxic proteins.