Integrating fermentation and separation for the production of advanced biofuels

The options for renewable energy in the aviation industry are limited to biofuels, since electrification of airplanes is unlikely to be feasible. Therefore, development of biofuels similar to current fuels is crucial for this industry. One option is the use of engineered microorganisms to produce long chained hydrocarbons (e.g., alkanes or isoprenoids) [1,2]. Currently, however, the production costs of these biofuels are too high to offer an economical alternative for conventional fuels. Improvements in both microorganism performance and process technology are needed.

The combination of  microorganisms and an immiscible product results in the tendency to form emulsions during the fermentation process. After product secretion, three steps have to be taken to recover the product: droplet growth, phase separation, and coalescence into a continuous oil layer. The last step proves to be the most challenging, due to the nature of the stabilizing molecules adsorbing at the droplet surface. Currently, multiple off-line centrifugation steps in combination with chemical de-emulsifiers are used to recover the product [3], adding costs and an environmental burden to the process.

We have developed an alternative recovery method that avoids expensive process technology and additives. This method can be integrated with the fermentation process, enabling process intensification strategies such as cell reuse and in-situ product recovery, hence lowering both investment and operating costs.

1. Westfall PJ, Gardner TS, Current Opinion in Biotechnology 22, 344 (2011)
2. Schirmer A, Rude MA, Li X, Popova E., Cardayre SB del, Science 329, 559 (2010)
3. Tabur P, Dorin G., US patent, US20120040396 A1 (2012)