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Characterization of switchgrass cell walls and their degradation using multiscale indentation techniques
Interest in biofuels has increased in recent years in order to reduce US dependence on foreign energy, to reduce greenhouse gas emissions, to develop new economies and to create new opportunities for agriculture among others. Research in the development of biotechnology is needed to increase fuel production from biomass, an effort that requires materials engineers, biologists, and plant scientists to work together. Switchgrass has been proposed as a viable biomass crop for further development because it has many advantages. Many biofuels are produced from cellulose and hemicellulose components of the cell walls, aspects of the plant that are closely connected to its genetics. In this study, a new protocol is implemented in order to test fresh samples. Micro- and nanoindentation techniques are used to quantify the cell wall structure with respect to cellulose and lignin content using a large phenotype test bed. These measurements are shown to be related directly to the cell wall composition and organization, which are assessed using biochemical assays and fluorescent microscopy. This method was able to highlight how components such as lignin affect the mechanical behavior of the material. Furthermore, nanoindentation was used to measure the cell wall properties during its degradation using two types of enzymes (xylanase and cellulase). Properties were monitored on a short time frame compared with current methods and were measured at different time intervals (30 min, 2 h, 4 h and 6 h). Measurements showed that the enzyme efficiency depends on the types of cells and that a high amount of lignin can slow the hydrolysis rate. Finally, samples of switchgrass were pretreated using liquid hot water treatment. Nanoindentation was used to determine how the pretreatment affects the cell wall properties and how it influences the enzymatic hydrolysis. Effects of the hydrolysis were also visible but not as effective as expected. Measurements such as these, that directly connect the mechanical and phenotypic properties, are expected to provide the basis for optimized biofuel production.
Alternative Energy|Mechanical engineering
Vennin, Severine, "Characterization of switchgrass cell walls and their degradation using multiscale indentation techniques" (2013). ETD collection for University of Nebraska - Lincoln. AAI3602993.