Abstract: Polyketides are one of the largest groups of natural products produced by bacteria , fungi , and plants . Many of these metabolites have highly complex chemical structures and very important biological activities, including antibiotic, anticancer, immunosuppressant , and anti- cholesterol activities . In the past two decades, extensive investigations have been carried out to understand the molecular mechanisms for polyketide biosynthesis . These efforts have led to the development of various rational approaches toward engineered biosynthesis of new polyketides .More recently, the research efforts have shifted to the elucidation of the three-dimentional structure of the complex enzyme machineries for polyketide biosynthesis and to the exploitation
of new sources for polyketide production , such as filamentous fungi and marine microorganisms . This review summarizes our general understanding of the biosynthetic mechanisms and the progress in engineered biosynthesis of polyketides .

Key words: Polyketides