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

Non-recombinant bacteria containing $β$ -galactosidase

lnsertional inactivation of $α$ -galactosidase in non-recombinant bacteria

lnsertional inactivation of $α$ -galactosidase in recombinant bacteria

Inactivation of glycosidase enzyme in recombinant bacteria

Solution

lnsertional inactivation of $α$ -galactosidase in recombinant bacteria

$α$ -galactosidase is a glycoside hydrolase enzyme that hydrolyse the terminal alpha galactosyl moieties from glycolipids and glycoprotein. It is encoded by the GLA gene. $β$ - galactosidase is an exoglycosidase, which hydrolyzes the $β$ -glycosidic bond formed between a galactose and its organic rhoiety.