CFD optimization of an air lift fermenter for Fusarium venenatum fermentation

Abstract

Airlift reactors are widely used in the field of microbial fermentation because of their simple structure and easy scale-up. This study investigated the enhancement of gas–liquid two-phase flow and mass transfer in a laboratory-scale airlift reactor for Fusarium venenatum fermentation through structural modifications. First, CFD modeling of the bubble reactor in the laboratory was performed and the reliability of the CFD model was verified by cold model experiments. Secondly, The addition of a baffle in the original reactor transforms it into an internal-loop split airlift reactor (ALR). The baffle was introduced into the initial reactor, and CFD was employed to predict the optimal installation position of the baffle. The results indicate that when a gap of 60 mm is maintained between the upper edge of the baffle and the liquid surface, a 40 mm gap between the lower edge of the baffle and the bottom of the reactor, and an A_d/A_r ratio of 1, the internal-loop split ALR exhibited a 23.55 % increase in gas holdup and a 30.07 % improvement in k_La compared to the original reactor., and the speed dead zone has been significantly improved. Following these specifications, baffe were installed, and the performance of the modified reactor was assessed against the original design during F. venenatum fermentation. The modified reactor demonstrated a significant enhancement in internal circulation, gas holdup, and mass transfer efficiency. Finally, the modified reactor was used for the fermentation experiment of F. venenatum. The fermentation results of F. venenatum showed that the glucose consumption rate of the modified reactor increased by 0.42 g/L/h, and the biomass increased by 3.49 g/L. The glucose conversion rate increased by 66.7 %, and the protein content increased by 3.69 %. These results showed that the internal-loop split ALR substantially improved the efficiency of the F. venenatum fermentation process.