Morphology, Broth Rheology And Flow Characteristics Of The Reactor In Industrial-scale Production Of Avermectin Fermentation

Avermectins are a series of 16-membered macrocyclic lactones produced by the actinomycete Streptomyces avermitilis. In this paper, we focused on sugar feeding, broth rheology and morphology of mycelium in industrial-scale production of avermectins by Streptomyces avermitilis. Then we made an analysis on the fluid dynamics in the fermentor. This work supplied the theory evidence for the enlargement and the optimization of avermectin fermentation.We established a kinetics model of avermectin fermentation and a rheological model of broth during the process of avermectin fermentation in procution scale, and performed non-linear regression analysis on the model parameters. The results showed that the predicted and experimental values fit well that the average deviation is about 5%. Then we studied the change of metabolic parameters and morphology of strain during batch fermentation after sugar feeding. The statistics of pellet projected area, perimeter, equivalent diameter and roughness were made by the aid of software, and results show that mycelium was more closely compact after sugar feeding. The pellet projected area was between 2200μm2 and 8000μm2 before sugar feeding, the range of which was between 1600μm2 and 5500μm2 after sugar feeding.Computational fluid dynamics (CFD) was introduced for the analysis of fluid dynamics in 150m3 fermentor of avermectins fermentation. The main object is to clarifying gas holdup, shear stress, mixing intensity, turbulent character and so on. The simulation results showed that the impellers mounted in the fermentor could not disperse gas thoroughly. The gas holdup was higher near impellers while it was lower in the bottom of tank. The liquid mixing effects were improved after increasing the bottom impeller diameter.