Researchers at Iowa State University are developing a mold-based process that breaks down the cellulosic corn fiber that is a by-product of the wet-milling process into sugars that can then be fermented into fuel ethanol.
The initial goal is to create a sequential biorefinery that can tap into what currently are the waste byproducts of corn processing. The process may be suitable for all ligno-cellulosic biomass material however.
The team, led by Hans van Leeuwen, an Iowa State professor of civil, construction and environmental engineering, uses a common brown-rot mold—Gloeophyllum trabeum—which produces (hemi)cellulases that will degrade (hemi)cellulosic compounds into sugars.
The process has a total reducible sugar yield of 12%. The ethanol yield with subsequent Saccharomyces fermentation is 4%. Potentially, we should be able to make 2x more sugar and 3x more ethanol per mass of fiber. We still need to improve on what we got so far. It took two years to get where we are now and the most important part happened suddenly in the last month.
I believe this is a breakthrough. But I also want to caution that we need to do a lot more research.—Prof. van Leeuwen
The team is working on patenting the process, which, among other things, contains a method to prevent the mold from consuming the sugar.
Use of the process in conjunction with existing wet-milling facilities could increase ethanol production by about 4%, or 160 million gallons per year, according to van Leeuwen.
Some of the next steps in developing the process are to apply it to distiller dried grains (DDG)—a byproduct of the dry-milling process typically used in the processing of corn kernels into ethanol—and switchgrass. The process may need different conditions or require some limited pretreatment with different fibers.
The two-year research project has been supported by a $150,000 grant from the US Department of Agriculture through the Iowa Biotechnology Byproducts Consortium, $130,000 from the Iowa Energy Center and materials from the ethanol industry.