Appl Microbiol Biotechnol. 2021 Sep;105(18):6707-6718. doi: 10.1007/s00253-021-11522-5. Epub 2021 Sep 3.
Pneumocandin B0, the precursor of the antifungal drug caspofungin, is a lipohexapeptide produced by the fungus Glarea lozoyensis. Oxidative stress and the resulting production of reactive oxygen species (ROS) are known to be involved in the regulation of pneumocandin B0 biosynthesis. In this study, the Glyap1 gene of Glarea lozoyensis, a homologue of the yeast redox regulator YAP1, was knocked out. The intracellular ROS levels of the resulting ΔGlyap1 strain were higher than in the wild-type strain, which was caused by the downregulated expression of superoxide dismutase (SOD) and catalase (CAT). Compared with the wild-type strain, ΔGlyap1 exhibited an oxidative phenotype throughout its life cycle, which resulted in significantly higher pneumocandin B0 production per unit biomass. In addition, ΔGlyap1 showed growth inhibition and decreased pneumocandin B0 production in the presence of CCl4, which leads to strong oxidative stress. To overcome the strain's sensitivity, a three-stage antioxidant addition strategy was developed. This approach significantly improved the growth of ΔGlyap1 while maintaining a high pneumocandin B0 production per unit biomass, which reached 38.78 mg/g DCW. Notably, this result represents a 50% increase over the wild-type strain. These findings provide new insights into the regulatory mechanisms that control pneumocandin B0 production under oxidative stress, which may be applied to improve the production of other secondary metabolites. KEY POINTS: • Glyap1 is involved in expression of redox and pneumocandin B0 synthesis-related genes. • Addition of a three-stage antioxidant alleviated the sensitivity of ΔGlyap1 strain. • The yield of pneumocandin B0 per unit biomass of ΔGlyap1 strain was 38.78 mg/g DCW.