# Enhancement of Monascus Azaphilone Pigments Production Without Citrinin Contamination by Targeting Overexpression of Histone Acetyltransferase MrEsa1 and Deletion of Polyketide Synthase PksCT

## TL;DR

Researchers improved pigment production in Monascus without making a harmful toxin by combining gene overexpression and deletion.

## Contribution

A dual-targeting strategy decouples pigment production from toxin synthesis in fungi.

## Key findings

- Deleting pksCT did not reduce MonAzPs yield in the overexpressed MrEsa1 strain.
- MrEsa1 overexpression counteracts the negative impact of pksCT deletion on pigment production.
- The modified strain showed accelerated growth and higher pigment yields compared to the wild type.

## Abstract

Monascus spp. are renowned for producing valuable Monascus azaphilone pigments (MonAzPs), yet their biosynthesis is intrinsically linked to the co-production of the mycotoxin citrinin, posing a significant safety challenge and limiting industrial application. Conventional approaches to disrupt citrinin synthesis often inadvertently reduce MonAzPs yield. To circumvent this limitation, we employed a dual-targeting strategy in Monascus ruber. In this study, we selected the mresa1-overexpressed strain—which can produce more MonAzPs and citrinin—as wild strain to construct a pksCT-deleted strain and explore whether pksCT deletion can affect the enhancement of MonAzPs caused by MrEsa1 overexpression. The results showed that the growth, development, and production of MonAzPs in △pksCT-M7::PtrpC-mresa1 were comparable to those in M7::PtrpC-mresa1, showing accelerated growth and higher MonAzPs yields than in M7. In addition, the relative expression levels of genes involved in MonAzPs synthesis in △pksCT-M7::PtrpC-mresa1 and M7::PtrpC-mresa1 showed the same trend compared with M7, indicating that MrEsa1 overexpression can resist the reduction in MonAzPs caused by pksCT deletion. This study establishes a novel and effective paradigm for decoupling desirable metabolite production from toxin synthesis in fungi, providing a strategic framework for the safe and enhanced production of MonAzPs.