Process improvement for fermentation coupling with foam separation: a convenient strategy for cell recycle

Abstract

AbstractApplications of fermentation coupling with foam separation technology show great advantages in many natural biosurfactants fermentation such as nisin, surfactin, and polymyxin E. However, only a few reports focus on process improvement, i.e. cells overflowing with foam. Because the cells also have hydrophobicity, it will overflow during foam separation, which decrease the productivity and contaminate the environment. Therefore, it is important to prevent cell from overflowing. In this study, a new approach was proposed to increase yield, using fermentation coupling with foam separation technology. Meanwhile, we tried to prevent cell from overflowing. This strategy was characterized by enrichment, recovery percentage, and inactivity percentage for product and cells. The results indicated pH was the most important factor in foam separation of polymyxin E. The optimal condition for fermentation coupling with foam separation was determined. The maximum total titer of polymyxin E reached 917 932.31 U (1147.4 U/mL) using coupling strategy that was 1.36 times more than total titer in shaken‐flask culture. Additionally, the adsorption mechanism for polymyxin E and cells was studied. The results indicated polymyxin E were mainly adsorbed on bubble, while the cells were partly in liquid form and partly adsorbed on undesired protein. Undesired protein can be considered as a stabilizer in foam separation of polymyxin E. Copyright © 2015 Curtin University of Technology and John Wiley & Sons, Ltd.