Highly efficient synthesis of lysergic acid using engineered budding yeast

Abstract

Lysergic acid (LA) is the basic precursor for the biosynthesis of various ergot alkaloids of pharmaceutical importance. The heterologous biosynthesis of LA in microbes is a promising method to reduce industrial dependence on highly costly and toxic crop-pathogenic ergot fungi. However, the biosynthetic efficiency of LA remains unsatisfactory because of the lack of effective pathways and low heterologous production performance. In this work, a microbial host, specifically a Saccharomyces cerevisiae strain, was constructed by applying a metabolic engineering strategy for efficient LA production. The SCH9 knockout was identified as a key factor for enhancing LA yield. Transcriptional analysis revealed that SCH9 deletion significantly enhanced peroxisomal metabolism and cellular translation. Accordingly, tailored approaches were designed to optimize the activities of two rate-limiting enzymes, EasC and CloA, in SCH9 deletion strains. The relocation of EasC to peroxisomes combined with PEX34 overexpression clearly increased the catalytic activity of these enzymes, increasing LA production by 2.31-fold. Moreover, spatial reorientation of the cytochrome P450 CloA and its reductase on the endoplasmic reticulum was performed, which improved electron transfer efficiency, resulting in a 36.8% improvement in LA production. These engineering strategies finally led to a 17.4-fold increase in the LA titre. The final engineered strain produced 509.8 mg L⁻¹ LA under 50 L fed-batch fermentation, yielding the highest reported titre for heterologous hosts. These findings demonstrated a green alternative to the current ergot-based routes, offering a versatile platform for the sustainable, large-scale fermentation of pharmaceutical ergot alkaloids.