Immobilization of Candida Rugosa lipase on Ca/Kit-6 used as bifunctional biocatalysts for the transesterification of coconut oil to biodiesel

•Candida Rugosa lipase (CRL) was immobilized on Ca/Kit-6 via adsorption method.•CRL/0.5Ca/Kit-6 possessed bifunctional roles in coconut oil transesterification.•Coconut oil conversion and biodiesel yield reached 95 and 98% under optimal reaction condition.•Stepwise addition of methanol favored coconut oil transesterification.•Catalyst showed higher catalytic activity under basic than acidic condition.