Mutant cellulose yields biofuel more easily

Genetic mutations to cellulose in plants could improve the conversion of cellulosic biomass into biofuels. Researchers at Iowa State University and seven other institutions studied Arabidopsis thaliana, a common model plant in research studies, and its cellulose synthase membrane complex, which produces the microfibrils of cellulose that surround all plant cells and form the basic structure of plant cell walls. These ribbons of cellulose are made of crystallized sugars. The crystal structure makes it difficult for enzymes to break down the cellulose to the sugars that can be fermented into alcohol for biofuels. Study leader Seth DeBolt, associate professor of horticulture at University of Kentucky, assembled a research team to see if genetic mutations in the plant membrane complex could produce what the researchers have called “wounded” cellulose that’s not as crystalline and therefore easier to break down into sugar. Mei Hong, a chemistry professor at Iowa State, had done previous studies of plant cell walls and used her lab’s solid-state nuclear magnetic resonance technology to study the cell walls created by the mutated system. The goals were to collect as much information as possible about the molecular structure of the cell walls to see if mutations to the plants resulted in changes to the cellulose. “We found that the crystalline cellulose content had decreased in the mutant cell walls,” Hong says. “We can quantify the degree of change, and be very specific about the type of change.” The cellulose microfibrils in the mutant cell walls, for example, were thinner than those found in normal plants, Hong says. The studies also found an additional type of cellulose with an intermediate degree of crystal structure. Hong says those findings suggest the genetic mutations did create differences in cellulose production and formation. The study, published in the journal Proceedings of the National Academy of Sciences, also reports the cellulose produced by the mutated plant could be more efficiently processed into the sugars necessary for biofuel production. “What this work suggests, in very broad terms, is that it is possible to modify cellulose structure by genetic methods, so that potentially one can more easily extract cellulose from plants as energy sources,” Hong says. The research team’s paper says developing techniques to modify the structure of plant cellulose in crops for better and easier conversion to fermentable sugars “could be transformative in a bio-based economy.” The National Science Foundation and the U.S. Department of Energy supported the study.