Forbaceous Plants as a Potential Feedstock for Cellulosic Ethanol Production: An Exploration of Composition, Recalcitrance, and Inhibition of Lignocellulosic Biomass Deconstruction
Angelos, Evan R.
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The reduction of petroleum consumption and the associated negative environmental impacts is becoming increasingly important. One method of reduction is the development of plant based ethanol for fuel use. First generation sources such as grain com have been plagued by problems. The production of ethanol from the second generation of biofuel feedstocks, (cellulosic biomass), theoretically, will fix these conflicts by sourcing feedstocks not sold in those vital markets. One of these sources, which has been indicated as an especially sustainable feedstock is the Mixed Species Prairie (MSP). Full utilization of MSPs however, has been delayed by previous analysis which has shown that a portion of this heterogeneous feedstock, forbaceous plants (forbs), may have low levels of fermentable sugars and are heavily recalcitrant (resistant to deconstruction by enzymatic processing). Four species representative species of diverse taxonomic backgrounds of these non-graminoid, non-woody plants are the subject of this work. A detailed compositional analysis of lignocellulosic material derived from each plant species was found to have smaller quantities of sugars than com stover, a graminoid second generation bioethanol feedstock. Furthermore, current commercial enzyme cocktails and purified enzyme mixtures used to deconstruct the forbs were found to be largely inadequate with respect to percent yield of monomeric sugars from polymeric sources. The cause of this was then investigated, we hypothesized that compounds found within the plants may have an inhibiting effect on the enzymes used. Differences of the hemicellulosic portion of the cell wall when compared to graminoids were also possible sources of recalcitrance.