(506d) Foam Separation for In Situ Biosurfactant Recovery

Biosurfactants are naturally occurring amphiphiles with a range of unique properties; including biodegradability and tolerance of a wide range of temperature and pH, making their use in a range of novel applications, such as environmental bioremediation and enhanced oil recovery, attractive. At present the utilisation of biosurfactants outside of high added value niche applications is hindered by a lack of economic production routes, with issues common to many bioprocesses being encountered; low upstream productivity and the subsequent need for costly downstream separation. In aerobic fermentations for production of extracellular biosurfactant nuisance foaming creates further difficulties.

Our current research is focused on applying our previously developed[1] controlled foam separation process to the production of the biosurfactant surfactin from Bacillus subtilis and investigating the controllability and scale up of the process. The effects of foaming during batch and fed batch surfactin producing fermentations have been studied, with foam generation being monitored over time. Foaming is associated with the surfactin producing stage of fermentations, which begins at the onset of glucose limitation and lasts for several hours. Treating the biosurfactant production and separation stages of the process as separate unit operations means that optimal conditions can then be established for each process, such as the aeration and agitation rates needed to achieve the oxygen mass transfer required to meet the biological oxygen demand of the cell population. For the uncontrolled foaming case in batch fermentations surfactin recovery was high, > 99%, with a typical total surfactin production of 100 mg. Similarly in fed batch fermentations uncontrolled foaming recovered 92% of surfactin produced, enriched by a factor of 48.