Penicillium expansum lipase (PEL) plays an important role in commercial production for its catalyze hydrolysis function. In order to improving the thermostability of the PEL, the lipase encoding gene was mutated by site-directed mutagenesis. Several recombinant vetors which contain double or triple mutant genes were constructed by overlap extension PCR using the cDNA of a random-mutant lipase ep8 (a single site mutant) as the template and two special primers were used to generate mutation site. The recombin...