Nitrogen source significantly increases Chaetomium globosum DX-THS3 β-glucuronidase production by controlling fungal morphology in submerged fermentation

Abstract Plant endophytic fungus Chaetomium globosum DX-THS3 can produce β-glucuronidase (GUS) for efficient hydrolysis of glycyrrhizin (GL) into more valuable compounds glycyrrhetinic acid monoglucuronide (GAMG). The low productivity of GUS and the lack of an effective strategy to control the fermentative morphology of C. globosum DX-THS3 have significantly limited its industrial applications. In this study, the effects of nitrogen source on GUS production and morphological changes in C. globosum DX-THS3 were investigated in shake flasks. Results showed that peptone was the optimal nitrogen source and had 3.5-fold higher GUS production by C. globosum DX-THS3 than the unoptimized source. C. globosum DX-THS3 had small circular pellets 1.3 ± 0.65 mm under 7 g/L peptone. Furthermore, a 5 L bioreactor was used to produce GUS. Under the optimal fermentation conditions, the GUS activity reached 792.17 U/mL. This work provides a strategy for designing the morphology of filamentous fungi by using nitrogen source in the industrial production of GAMG.