The GlycFree (_DE3) strainÊis the _DE3 lysogen of E. coli M226 strain (M226((_DE3)). It has been engineered for expression of sugar-free recombinant proteins in E. coli. Some glycosyltransferases have ability to catalyze a self-glycosylation reaction using UDP-glucose (UDPG) as glucose donor (1). ÊAs such, these proteins can be aberrantly glycosylated during expression in common E.coli strains like BL21 and its derivatives. GlycFree (_DE3) is anÊE. coliÊstrain defective in the synthesis of UDP-glucose. GlycFree(_DE3) allows to produce non-glycosylated forms of target proteins in native conformation and preserve their biological activity.