Biosynthesis of acetylacetone inspired by its biodegradation

BACKGROUND: Acetylacetone is a commercially bulk chemical with diverse applications. However, the traditional manufacturing methods suffer from many drawbacks such as multiple steps, harsh conditions, low yield, and environmental problems, which hamper further applications of petrochemical-based acetylacetone. Compared to conventional chemical methods, biosynthetic methods possess advantages such as being eco-friendly, and having mild conditions, high selectivity and low potential costs. It is urgent to develop biosynthetic route for acetylacetone to avoid the present problems. RESULTS: The biosynthetic pathway of acetylacetone was constructed by reversing its biodegradation route, and the acetylacetone was successfully produced by engineered Escherichia coli (E. coli) by overexpression of acetylacetone-cleaving enzyme (Dke1) from Acinetobacter johnsonii. Several promising amino acid residues were selected for enzyme improvement based on sequence alignment and structure analysis, and the acetylacetone production was improved by site-directed mutagenesis of Dke1. The double-mutant (K15Q/A60D) strain presented the highest acetylacetone-producing capacity which is 3.6-fold higher than that of the wild-type protein. Finally, the strain accumulated 556.3 ± 15.2 mg/L acetylacetone in fed-batch fermentation under anaerobic conditions. CONCLUSIONS: This study presents the first intuitive biosynthetic pathway for acetylacetone inspired by its biodegradation, and shows the potential for large-scale production.