Abstract

A computational fluid dynamics (CFD) model was developed and validated against experiments for a laboratory-scale 5-L bioreactor. Numerical simulation was performed to describe the bioreaction of Streptomyces atratus SCSIO ZH16 fermentation for ilamycin E production with the dynamic changes in viscosity of the fermentation broth due to biomass growth and decay. This model can account for the two-way coupling between the fermentation environment and medium, which enabled the analysis of the relationship between the broth viscosity, flow field, mass transfer, and macroscopic fermentation performance. This work represents the first integration of Streptomyces fermentation with CFD, enabling the simulation of flow field and mass transfer under varying stirring speed, aeration rate, and viscosity during Streptomyces fermentation. A suggested favorable range of fermentation broth viscosity (10–30 mPa s) was identified for ilamycin E production by S . atratus SCSIO ZH16 fermentation. Furthermore, the addition of sorbitol was used to adjust the viscosity of the fermentation broth in the later stages of fermentation. Experimental evidence, including elevated OUR/CER and up-regulated respiratory-chain gene transcription, suggested that the yield improvement was primarily associated with enhanced oxygen transfer resulting from reduced broth viscosity. This research offers a practical strategy for the process intensification and industrial scale-up for such bioreactors.