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The role of solvent extraction in the chemical characterization of corn stover feedstock



Graduation date: 1996The consequences of extracting com stover feedstock with either 95% ethanol or hot\ud water prior to the chemical analysis of the macrocomponents of that feedstock have been\ud determined. Reports by others have recommended the removal of extraneous substance\ud by solvent extraction prior to chemical analyses (Browning, 1967; TAPPI, 1988). The\ud 95% ethanol extraction evaluated in this study is currently the "standard" method\ud recommended by the National Renewable Energy Laboratory, Golden, Co. Hot water\ud extractions were tested as a simple, less time consuming and less expensive alternative to\ud ethanol extractions. Compositional analyses involved the quantification of glycans, Klason\ud lignin, acid soluble lignin, ash, protein, acetic acid, and uronic acids.\ud The summative analysis of native, ethanol extracted and water extracted\ud feedstocks were all in the range of 97 to 98%. Ethanol extractions removed 4.9% of the\ud feedstock dry weight, compared to 17.2% of the dry matter being extracted with hot\ud water. The extractives obtained via ethanol had negligible amounts of glycans. In\ud contrast, the water extracted solids contained nearly 10% of the native feedstock total\ud glucan. Pre-extracting the feedstock with ethanol had little effect, relative to the native\ud feedstock, on the quantification of glycan components. In contrast, the water extracted\ud feedstock measured significantly lower in total glucans and total glycans than the native\ud feedstock. The lower values associated with the water extraction were due to the actual\ud extraction of glucans from the feedstock, and not due to analytical interferences associated\ud with the extractives. Ethanol and water extracted feedstocks measured significantly lower\ud in Klason lignin than the corresponding native feedstock. This was presumably due to the\ud removal of Klason lignin impurities present in the native feedstock, and not due to the\ud extraction of lignin itself.\ud The combined results from this study indicate that an informative approach to the\ud analysis of com stover feedstock would include the pre-extraction of the feedstock with\ud hot water prior to further analyses. The appropriate macrocomponent analyses should\ud then be done on both the extracted feedstock and the "extractives" obtained from that\ud feedstock. Analysis of the extracted feedstock, as compared to the native feedstock,\ud would provide more accurate estimates of the cellulose and lignin content of the\ud feedstock. The summative analysis of both the extracted solids and the extractives will\ud provide a reliable estimate of the total amount of carbohydrate potentially available in the\ud feedstock for microbial fermentation to ethanol

Year: 1996
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