SHuffle is a mutant E.coli strain lacking the two reductases (trxB and gor) with an additional suppressor mutation (ahpC) which restores viability, allowing the formation of stable disulfide bonds in the cytoplasm. Under these conditions thioredoxins are in their oxidized state, converting them from reductases to oxidases. Proteins that require disulfide bonds for their folding thus can be oxidized and form stable disulfide bonds within the cytoplasm. Additionally, SHuffle strains express the disulfide bond isomerase DsbC within the cytoplasm. This feature greatly enhances the fidelity of disulfide bond formation in the cytoplasm, and proteins with multiple disulfide bonds are correctly oxidized to significantly higher yields.