Team:Calgary/PHB Fermentation
PHB Fermentation
Overview
In this stage of the process, VFA-rich stream from the previous step is fermented by engineered E. coli to produce PHB. This continuous fermentation process occurs in a 5L stirred-tank bioreactor at 37°C and under anaerobic conditions. A continuous flow of the VFA-rich stream is generated by the pump. To achieve continuous fermentation, a mechanical self-cleaning filter with 0.2-micron filters is used to separate and recycle bacteria back to the bioreactor. The resulting bacteria-free harvest stream that contains PHB is then passed to PHB extraction and water recovery. The proposed process is shown in Figure 1.
Design options considered
Other considered design options include:
- External membrane bioreactor (EMB)
- Immersed membrane bioreactor (IMB): specifically the hollow fiber and the flat sheet designs
- Stirred-tank bioreactor with self-cleaning filter separation
The major disadvantage of membrane bioreactors is fouling. Because of fouling, frequent filter cleaning and filter replacement might be required resulting in higher crew-time requirements and transportation costs to supply replacement membranes.
The stirred-tank bioreactor, on the other hand, provides continuous agitation and easy temperature control, while the implementation of the self-cleaning filter reduces fouling. An example of a stirred tank bioreactor can be found following this link, certain specifications - like power, mass and volume of the following model were used in the ESM parameters estimation. An Example of smaller-scale self-cleaning filter can be found on the Eaton