There are two versions of SHuffle® based on two different E. coli strains. SHuffle® T7 (NEB #C3026) is based on E. coli K12 while SHuffle® Express (NEB# C3028), SHuffle® T7 Express (NEB# C3029) and SHuffle® Express T7 LysY (NEB# C3030) are all based on E. coli B. We have observed varying levels of folding and expression within the two different SHuffle® cell lines (K12 vs B), depending on the protein. Currently we can not predict which SHuffle® cell line will be more successful in folding a given disulfide-bonded protein. We therefore recommend comparing the expression of your protein of interest in both SHuffle® strains (NEB #C3026 and #C3029) as the initial experiment. Once the optimum SHuffle® strain type is decided, optimization of expression conditions (e.g. temperature, inducer strength and timing, etc..) is recommend. All SHuffle strains can be used for non-T7 promoters (e.g. lac and ara promoter expression vectors). For T7 promoter expression vectors, we recommend either SHuffle T7 Express (NEB #C3029) or SHuffle T7 (NEB #C3026). For toxic T7 promoter expression, we recommend SHuffle® T7 Express lysY (NEB #C3030).