Microorganisms can sometimes produce chemicals and fuels as cheaply as conventional methods, while using sugar instead of petroleum. Technology developed by researchers at Argonne National Laboratories could help reduce the cost of production of chemicals or fuels made using microorganisms, and potentially increase the range of such materials. It does this, in part, by keeping the bugs alive for longer. The researchers recently announced that Nalco, a company based in Naperville, Illinois, will commercialize the technology.
The new tool uses an advanced form of electrodeionization (EDI), a technology used to make ultrapure water. The advanced EDI provides a better way to control the acidity of the solution in which an organism grows, and this helps optimize the microbe-driven production process. It also efficiently removes the chemicals that microorganisms make, allowing the process to run continuously. By creating a less harmful environment for growth, the tool could make it easier to engineer microorganisms for producing new chemicals.
In conventional EDI, resins pull charged molecules, or ions, out of a solution. An electric field then moves the ions to a membrane that allows the ions to pass but filters out other chemicals. The system can also control the acidity of the solution by using the electric field to split small amounts of water into more acidic or basic components, and then selecting one or the other to be removed through the membrane.
In a conventional EDI system, the resin takes the form of tiny beads, packed randomly so that there are often poor connections between them. There is a trade-off between the conductivity of the resin, which affects the efficiency of the system, and its porosity which affects how fast it can produce chemicals.
The Argonne researchers have developed what they call resin wafers, which combine multiple resins, binding agents, and additives to improve the conductivity and porosity of the material. The approach also keeps electricity costs low–just a few cents of electricity is needed to produce a pound of a chemical that sells for a dollar, says Seth Snyder, who is leading the project at Argonne.
The technology could be used first for cheaper fermentation. One of the biggest industrial applications of fermentation is the production of plastics precursors such as succinic acid, and food additives such as citric acid. But these acids need to be counteracted by adding large quantities of base materials, such as calcium hydroxide, which are then converted in the process to waste products such as gypsum.
David Dodds, president of Dodds and Associates, a longtime industry consultant, says the calcium hydroxide treatment is the most expensive part of fermentation, with the possible exception of the costs of the sugar needed to feed the organisms. The new tool eliminates the need to add calcium hydroxide altogether by precisely controlling acidity, he says.
The Argonne technology also makes continuous production possible. In conventional fermentation, organisms are grown in a tank where they excrete a product until it reaches a concentration that is toxic to the organism. The contents of the fermentation tank are then poured out, and the process starts again. With the new EDI tool, the chemical product can be removed as it is made, so concentrations stay low. Microorganisms can continue producing chemicals for 10 times longer.
The new tool may also aid in engineeing organisms for new applications. It makes it unnecessary to use acid-resistant organisms, or organisms that can tolerate high concentrations of the chemical they produce.
The Argonne researchers have demonstrated the production and purification of chemicals at a small pilot-scale plant. The partnership with Nalco will make production versions of the system available for companies and other researchers. Although it’s not yet known precisely how much the equipment will cost for commercial production, Dodds says, “It looks to me that there will be significant cost savings.”
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