Glycoside hydrolases (or glycosidases), are enzymes that break glycosidic bonds.  Glycoside hydrolases typically can act either on α- or on  β-glycosidic bonds, but not on both.  This specificity allows researchers to obtain glycosides in high epimeric excess, one example being Wen-Ya Lus conversion of D-Glucose to Ethyl β-D-glucopyranoside using naturally-derived glucosidase.  It is worth noting that Wen-Ya Lu utilized glucosidase in a reverse manner opposite to the enzymes biological functionality: