[Construction and fermentation regulation of strains with high yields of echinocandin B].

Echinocandin B (ECB) is a key precursor of the antifungal drug anidulafungin. It is a secondary metabolite of <i>Aspergillus nidulans</i>, and its titer in fermentation is significantly affected by the ECB synthesis pathway and cell morphology. In this study, the key genes related to the transcription activation, hydroxylation, and cell morphology during ECB biosynthesis were investigated to increase the fermentation titer of ECB and to change the cell morphology of Aspergillus <i>nidulans</i> to reduce the viscosity of the fermentation broth. The results indicated that after overexpression of <i>ecdB</i> and <i>ecdK</i>, the ECB titer increased by 25.8% and 23.7%, respectively, compared with that of the wild-type strain, reaching (2 030.5±99.2) mg/L and (1 996.4±151.4) mg/L. However, the deletion of <i>fksA</i> associated with cell wall synthesis resulted in damage to the cell wall, affecting strain growth and product synthesis. The engineered strain overexpressing <i>ecdB</i> was fermented in a 50-L bioreactor, in which the ECB titer reached 2 234.5 mg/L. The findings laid a research foundation for the subsequent metabolic engineering of this strain.