Application of a Dynamic Method for the Volumetric Mass Transfer Coefficient Determination in the Scale-Up of Rhamnolipid Biosurfactant Production

Biosurfactants are widely used for industrial, agricultural, food, cosmetics, and pharmaceutical applications. However, much of the work on biosurfactant production is still in the laboratory stage. In addition, there is a lack of fundamental knowledge about the scale-up of biosurfactant production. This article addresses this issue and describes dynamic methods for obtaining scalable data for aerobic fermenters. To achieve this objective, the present work aims to study the scale-up of the rhamnolipid production process from 2.5 to 20 L of an aerated and agitated bioreactor. A similar scale-up trend in both Pseudomonas aeruginosa growth and biosurfactant production under optimum conditions demonstrated that the scale-up protocol based on the constant oxygen transfer coefficient is successfully implemented in this work. A maximum rhamnolipid production of 8.3 g L-1 was achieved after 1 week in the 20-L fermenter, which was 10% better than that of the 2.5-L fermenter at the same time period. This difference may be due to the change of aeration from 1.0 vvm (volume of air per volume of medium per minute) on the small scale to 2.0 vvm on the large scale. However, the comparable results obtained on both scales confirmed that the scale-up protocol works for rhamnolipid production. Based on our results, we consider that this method is perhaps the most helpful tool for successful scale-up of biosurfactant production and for the determination of the optimal conditions at the production scale. The results of this work will help the researchers to have a good prediction of scale-up in this field.