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Utilization and characterization of corn -based by -products from the ethanol production facilities

Jongwon Byun, University of Nebraska - Lincoln

Abstract

The current US production of ethanol relies predominantly on starch-based material which primarily uses corn as the raw material. There are two distinct processes for the conversion of corn to ethanol, dry grind and wet milling. Distillers’ grains and corn fiber are the by-products of the dry grind and wet corn milling industries, respectively. Availability of distillers’ grains and corn fiber at the ethanol plant and their high levels of lignocellulosic material, oil and protein make them attractive feedstock for conversion to ethanol and other value-added products. ^ Dilute sulfuric acid hydrolysis of distillers’ grains and corn fiber to monomeric sugars was investigated. Formation of furfural, an inhibitor to the fermentation process, from the decomposition of monomeric sugars was monitored. The results provided a range of experimental conditions for the pretreatment of distillers’ grains and corn fiber and examined the suitability of these pretreated substrates for enzyme hydrolysis step. ^ Stagewise dilute sulfuric acid pretreatment and enzyme hydrolysis for the conversion of DDG, defatted DDG, WS, and corn fiber to monomeric sugars were investigated to increase the concentration of monomeric sugars in the hydrolyzate which in turn is expected to increase ethanol concentration in the fermentation products. In this scheme, after the completion of the first-stage of the pretreatment, the liquid substrate was separated and reused in the succeeding pretreatment stage with fresh substrate. The substrate from each stage was also subjected to enzyme hydrolysis in a separate experiment. Experiments were also performed to study the effect of removing oil from the samples prior to the pretreatment step. The formation of the inhibitory products was monitored during the course of the stagewise pretreatment process. ^ Another objective of this research was to explore the potential for the extraction and characterization of proteins from by-products as they contain significant amounts of proteins along with carbohydrates. Experiments were performed to fractionate and quantify the four major classes of corn proteins in the DDG, WS, and corn kernel samples based on their solubility in selected solvents. Extraction and characterization of zein proteins from DDG, WS, and corn kernel was investigated using aqueous ethanol. The effects of pH, temperature, and reducing agents on the extraction yield were examined. The extracted zein protein was characterized using HPLC, SDS-Page, and MALDI-TOF mass spectrometry to study its functional properties. The properties of extracted zein proteins were compared with a commercial zein protein to determine any changes to the chemical and/or molecular structure that may have occurred during the course of the dry grind process.^

Subject Area

Engineering, Chemical

Recommended Citation

Byun, Jongwon, "Utilization and characterization of corn -based by -products from the ethanol production facilities" (2008). ETD collection for University of Nebraska - Lincoln. AAI3338828.
http://digitalcommons.unl.edu/dissertations/AAI3338828

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