Robert A. Clyde is trying to make this plea futile with equipment that speeds up naturally occurring reactions. A chemical engineer turned entrepreneur, Clyde has spent the seven years since he retired inventing and patenting such devices. keep thinking I'm going to settle down and play tennis every he says. I just keep getting these ideas. Clyde's latest idea ventures into the realm of industrial microbiology, a mutlibillion-dollar industry that takes advantage of nature's smallest alchemists -the microbes. These microscopic organisms produce enzymes that catalyze the myriad of biochemical reactions that turn sugar water into wine, cow's hide into leather, and toxic chemicals into less toxic ones, to name but a few. Clyde hopes to facilitate some of these microbe-mediated transformations with a stack of discs and a rotary motor. To construct his basic bioreactor, or fiber fermenter, Clyde arranged 80 silverdollar sized polyester discs along a 4 inch long segment of a thin metal rod, separating each paper-thin disc with a small cardboard washer. shaft of fibers fits inside a glass pipe that contains the reaction medium, or Clyde's bioreactor involves two main concepts: immobilizing bacteria and moving them relative to the medium. floating freely, micron-sized cells are difficult to separate from solution, whereas immobilized bacteria are relatively easy to manipulate. First, you attach bacteria to the fibers and run the says Clyde, referring to an apparatus and methodology he patented a year ago. Then you can either drain off the product and leave the bacteria attached inside the reactor or you can take the carrier out. Researchers have immobilized living cells on or in various substances since the early sixties. But according to Clyde, reaction broths diffuse too slowly through conventional carriers -such as ceramic, charcoal, or polymeric gels -which also occupy too much volume for the amount of bug-clinging surface area they provide. In his search for a better carrier, Clyde tried cotton string, soon followed by acrylic and polyester discs. The bacteria go right on the fibers and stay on until you knock them off, says Clyde, who's not sure if the cells are entrapped among the fibers or held by electrostatic attraction (cells are slightly positive). Frankly, I think it's a little bit of both. Soon after he designed an apparatus to hold bacteria to fibers in a biological reactor, Clyde began testing the device for its practical application. One day, while tinkering around with a basic sugar-toethanol fermentation, he began rotating the shaft of bacteria-clad fibers with respect to the reaction broth. result? almost fell off my lab stool, he told scientists at the meeting last month in Washington, D.C., of the American Chemical Society (ACS). Within ten minutes, carbon dioxide began foaming right out of the fermenter. Clyde's new patent for moving the substrate relative to the reaction solution was issued Oct. 4. North Carolina inventor compares his rotating fiber fermenter to the innards of a car. If you stop while the engine's running, your car would overheat if it weren't for the fan, which reduces the fluid film of air on the radiator, Clyde says. The same goes for bacteria. A layer of stagnant fluid surrounds the surface of every cell, preventing fresh reaction broth access to the bacteria's catalytic enzymes. By moving the broth relative to the bacteria, Clyde theorizes he's reducing that fluid film layer, thereby speeding up the reaction, sometimes as dramatically as 150 percent. It used to take me 25 hours to get an 80 percent alcohol yield, he says. When I rotate the fibers, it only takes 10 minutes. Clyde has also turned his fiber-bound bacteria through solutions of uranium, chromium, silver and other ionic metals. Because many microbes synthesize negatively charged metal-binding proteins, such as metallithionein, the organisms quickly accumulate positively charged metals. For years, scientists have used microorganisms to recover valuable minerals and remove harmful ones from contaminated wastewater. But Clyde claims that industries have not taken full advantage of bacteria's metal-leaching abilities because they don't know how to do it economically. Using bacteria immobilized on c)
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Jul 1, 1984
A S Mikhnevich 
Open Access