A spinning cloth disc reactor (SCDR) markedly accelerates the rate of enzyme reactions, report researchers at the University of Bath, Bath, U.K. Centrifugal force spurs the spreading of thin film on and through a cloth containing immobilized enzyme that rests on top of a spinning horizontal disk, leading to high mass-transfer rates and rapid mixing, they explain. "Overall, our results indicate that the SCDR is an innovative, superior and robust technology for enhancing enzyme reactions, taking enzyme reactors beyond the current state of the art," says co-developer Darrell Patterson of the university's dept. of chemical engineering. The SCDR differs from conventional spinning disc reactors and rotating packed beds, and is a separate and new class of spinning-disc-type reactor for process intensification, he emphasizes.
"Our work has shown that this system produces enhanced reaction rates compared to conventional enzyme reaction systems. Our initial work has been on the conversion of a simple oil system (tributyrin hydrolysis), which shows us if the reactor could be used practically for the treatment of oily wastewaters, for example. We found that the conversion and reaction rates in the SCDR were significantly higher than that in a conventional batch stirred-tank reactor under comparable conditions. The SCDR was also simple to control — disk/cloth spinning speed and reactor feed flow rate gave good control of reaction rate and conversion," Patterson notes.
The researchers used a 1.5-mm-thick unbleached woolen cloth and ran trials at various rotational speeds and flow rates (Figure 1).
"…The most exciting result is that the immobilized lipase showed excellent stability to repeat reactions in the SCDR: for the tributyrin system, 80% of the original lipase activity was retained after 15 consecutive runs," adds co-developer Emma Emanuelsson. More details appear in a recent article in Chemical Engineering Journal.
"I think it [the SCDR] is best suited to small-scale high-value applications where the high selectivity of an enzyme is valuable, such as in the pharma and/or fine chemicals industry," comments Patterson.
The team now also is working on using the device for biodiesel synthesis and pharmaceutical reactions. "…We are more than happy to test this new reactor on other reactions if there is an interest from others," he says.
"…We now are moving onto synthetic supports that allow us a wider range of chemical compatibilities, control over the mesh size and free volume within the mesh and, most importantly, allow us to vary enzymes and immobilization techniques more freely," Patterson notes. "For the enzyme work, we are looking at a range of polymer meshes with high surface areas. We are also applying the SMDR [a term the researchers use to denote the use of mesh not just cloth] concept to photocatalysis, with TiO2-coated meshes…"
Once the laboratory evaluations are complete, the researchers hope to interest a company in helping them take the system to the pilot scale.
Scale-up to industrial capacity is straightforward, explains Patterson: "The SMDR will be 'numbered up' if increased volume is required — this makes scale-up robust and simple, since the performance can be easily predicted based on the smaller-scale work." He foresees maximum disc size as 1 m but believes, in most cases, the disks would be smaller.