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

• Non-recombinant bacteria containing  β-galactosidease 

• Insertional inactivation of α - galactosidase in recombinant bacteria

• Insertional inactivation of α-galactosidase in recombinant bacteria

• Inactivation of glycosidase enzyme in recombinant bacteria

C.

Insertional inactivation of α-galactosidase in recombinant bacteria

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 hydrolyses the terminal alpha-galactosyl moieties from glycolipids and glycoprotein. It in encoded by theGLA gene. β-galactosidase is an exoglycosidase, which hydrolyzes the β-glycosidic bond formed between a galactose and its organic rhoiety.