The work presented here was undertaken to help understand how different cellulosic biofuel treatments alter the chemistry of lignin in a biofuel feedstock. Production of alcohol from plant matter via a fermentation pathway requires the application of a pretreatment step to prepare the plant fibers for enzymatic hydrolysis. The enzymatic hydrolysis then breaks down the plant polysaccharides into fermentable sugars, which are then converted to alcohol through fermentation. A quick search of the scientific literature on the subject would reveal that numerous different biomass pretreatment methods, with very different process chemistries, have been investigated in detail in regards to their process chemistry, yield, and economics. However, while it is widely recognized that the lignin present during biofuel production plays an important role in enzymatic hydrolysis kinetics, relatively little work has been done to elucidate the changes in the lignin chemistry that may occur during biomass pretreatment. This may be due in large part to the intractable nature of the lignin that results, which usually exits these processes as part of a water insoluble mass of material remaining after enzymatic hydrolysis or fermentation. This insoluble mass contains most of the lignin that entered the process along with a significant portion of residual polysaccharide and inorganic ash. Isolating a high purity lignin for characterization purposes remains a challenge. This work approached that problem by utilizing the enzymatic mild acidolysis lignin (EMAL) procedure previously developed to isolate lignin from Kraft pulps and wood flour. The EMAL procedure was applied to extract lignin from fermentation residual solids resulting from biofuel production from a primarily Douglas-fir feedstock that had been pretreated using either a mild bisulfite digestion or a wet oxidation pretreatment. The chemistry of the extracted lignins was then compared to lignin extracted from the untreated feedstock.

Isolation and characterization of lignin from co-product streams in biofuel production

247th National Meeting (2014)

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