A combined fermenter-extractor-separator has been developed by researchers at Iowa State University. Because it uses the Taylor vortex design, it is gentler than traditional fermentation, extraction, and separation techniques, which makes it attractive for microbe production and other biotech applications. Called the Taylor Vortex Fermenter-Extractor-Separator, it is envisioned as a bioreactor for small volumes of value-added products and for process intensification.
It could be a significant improvement over the types of fermenters the biopharma industry inherited from the chemical industry. The biopharma industry “has gone a fair distance using them, but non-uniform mixing is not ideal for microorganisms,” Dennis Vigil, PhD, professor, department of chemistry and geology engineering at Iowa State University, tells GEN.
With this new bioreactor, “aerobic fermentation can be carried out using substantially less gas because of much higher mass transfer rates than in conventional bioreactors,” Vigil says. Importantly, “the fluid is gentle on the cells, while still providing uniform mixing.”
“Homogenous mixing is also important in reducing genetic drift and maintaining a high-producing environment rather than enriching low-producing mutants,” colleague Zengyi Shao, PhD, professor, emphasizes.
Advantage: the Taylor vortex
“This is a simple device, with an outer cylinder and an inner, concentric cylinder,” Vigil says. “The fermentation broth goes in the space between the two cylinders. When the inner cylinder spins, it gives rise to Taylor vortices,” which enable uniform mixing and low cell lysing.
This approach distributes power more evenly than stirred tank bioreactors. “In traditional bioreactors, the power to drive the impellors is one of the significant costs of mixing in tanks,” adds David Nathan, program director of technology at BioMADE, which sponsored the research. “This Taylor vortex bioreactor has much more efficient power usage in terms of mixing.”
Extraction is accomplished by leveraging the bioreactor’s hydrodynamic flow pattern. When extraction fluid is added, it removes the target product molecules from the fermentation broth. In these experiments, Shao says, “The target molecules were C16 and C18 fatty alcohols that are toxic to cell growth.” Hence, by transferring these products into a separate fluid phase, the toxicity effect on cells can be mitigated.
Same-device separation can occur because the inner rotating cylinder is hollow. It is, essentially, a centrifuge that separates the aqueous fermentation broth and organic extraction phases of the solution.
The 14-L Taylor Vortex Fermenter-Extractor-Separator has just achieved proof of concept. Eventually, larger versions may help users redeploy small fermentation facilities and produce small volumes of value-added substances. In addition to extracting and separating fatty alcohols from fermentation solution, Taylor vortex reactors have also been used to culture algae and mammalian cells.
Vigil and Shao have additional projects underway that use it to produce a carotenoid as a nutraceutical, and a polymer precursor. “There are still a lot of things to learn,” Vigil says.
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