Effect of biosurfactant sophorolipids on Rhizomucor miehei lipase fermentation by Aspergillus oryzae

Abstract In this study, the effect of biosurfactant sophorolipids on Rhizomucor miehei lipase (RML) fermentation by Aspergillus oryzae was investigated. With the exogenous addition of 0.3% (w/v) sophorolipids in the initial medium, the RML activity reached 430.0 U/mL, an increase of 25.0% compared to the control group. Subsequently, the physiological metabolic responses of A. oryzae to the addition of sophorolipids were further explored. The results showed that although sophorolipids had almost no effect on the RML secretion, it would affect the morphology of the cells. During the late phase of the fermentation, the proportion of middle pellets, which were generally considered as an energetic and stable state for enzyme production was increased with the addition of sophorolipids. Simultaneously, the viscosity of fermentation broth was reduced, thereby contributing to the oxygen transfer and RML production. Finally, it could be found that the addition of sophorolipids significantly increased the content of precursor amino acids, especially for those rank first and second of the RML composition, and it could promote the synthesis of RML.