The colonies of recombinant bacteria appear white in contrast to blue colonies of non-recombinant bacteria because of

The colonies of recombinant bacteria appear white in contrast to blue calories of non-recombinant bacteria because of insertional inactivation of alpha galactosidase in recombinant bacteria. Alpha galactosidase is a glycoside hydrolase enzyme that hydrolyse the terminal alpha galactosyl moieties from glycolipids and glycoprotein. It is encoded by the GLA gene. $\beta$-galactosidase is an exaglycosidase, which hydrolyzes the $\beta$-glycosidic bond formed between a galactose and its organic rhoiety.