Avermectin is a macrolide compound produced through fermentation by S. avermitilis,and it's a kind of widely used biological pesticide. This paper investigated the function of maltose transporter system and the relation between the expression of maltose transporter system and the yield of avermectins in S. avermitilis. The malEFG gene was amplified by PCR using genomic DNA of S. avermitilis as template,and then was inserted into multi-copy vector and integration vector,respectively. Each expression vector w...