Cost-effective production of squalene using Yarrowia lipolytica via metabolic engineering and fermentation engineering.

Squalene is a triterpene with various biological applications. However, the conventioneer squalene industry is limited by complex extraction processes and environmental pollution, necessitating an environmentally sustainable solution to the increasing demand for squalene. Microbial synthesis is a potentially green and efficient method of producing squalene. Acetyl-CoA is a key precursor of squalene. First, we investigated the effects of enhanced acetyl-CoA supply on squalene production, lipid content, and total fatty acid content in Yarrowia lipolytica. Then, strain YLACLH2 with a squalene production of 232.29 mg/L was obtained by co-overexpressing YlACL2 and YlHMG1. Subsequently, the squalene production of YLACLH2 was increased to 514.33 mg/L by fermentation engineering, optimizing fermentation conditions including temperature, media volume, C/N ratio, shaker flask type and medium type. Finally, we investigated the synthesis efficiency of squalene in Y. lipolytica by acid-hydrolyzed sugarcane molasses (AHM) and waste cooking oil (WCO) as carbon sources with optimized fermentation conditions. This study showed that Y. lipolytica has the potential to produce squalene industrially using low-cost substrates. Our study findings provide reference for engineering Y. lipolytica to produce squalene using low-cost substrates and in an environmentally sustainable manner.