Factors Affecting Starch Conversion to Ethanol in Dry Grind Corn Process
Sharma, Vivek
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Permalink
https://hdl.handle.net/2142/86070
Description
Title
Factors Affecting Starch Conversion to Ethanol in Dry Grind Corn Process
Author(s)
Sharma, Vivek
Issue Date
2007
Doctoral Committee Chair(s)
Singh, Vijay
Department of Study
Agricultural Engineering
Discipline
Agricultural Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Agricultural
Language
eng
Abstract
Factors affecting corn starch conversion to ethanol were evaluated to investigate the lack of correlation between ethanol concentration and corn starch content in dry grind corn process. Effect of amylose:amylopectin ratios and resistant starch in corn starch on ethanol concentration was evaluated with four enzyme treatments operating at varying temperature and pH liquefaction conditions. Final ethanol concentrations decreased with increase in amylose content in starch treatments. However, when high temperature liquefaction enzymes where used, starch treatments with higher amylose contents resulted in higher ethanol concentrations, compared to low temperature liquefaction enzymes. Starch treatment with ∼100% amylopectin resulted in highest ethanol concentrations among starch treatments irrespective of enzymes used, indicating higher digestibility of amylopectin irrespective of high or low temperature processing condition. Resistant starch was found to be higher for starch sample with 30% amylose compared to the starch sample with 0% amylose, indicating higher amylose leads to higher resistant starch. Higher resistant starch in sample resulted in lower starch to sugar conversion by enzymes and, therefore, in lower final ethanol concentrations. Higher temperature liquefaction hydrolyzed a larger portion of resistant starch, resulting in higher ethanol concentrations and lower final residual solids. Resistant starch content for starch samples with 30% and 0% amylose decreased or remained similar after liquefaction and decreased further after SSF, for all four enzyme treatments. Four commercial corn hybrids with similar starch content but varying ethanol concentration yield (evaluated by conventional dry grind corn process) were investigated for amylose:amylopectin ratios and resistant starch. The two low ethanol yielding hybrids had higher amylose and resistant starch content whereas the two higher ethanol yielding hybrids had lower amylose and resistant starch content. Total starch content had a weak correlation (R2 = 0.24 and 0.35) with final ethanol concentrations whereas initial resistant starch content had a high correlation (R2 = 0.96 and 0.90) with final ethanol concentrations for the four corn hybrids. Amylose and resistant starch content can be used to assess if the corn hybrids are favorable for hydrolysis and fermentation in the dry grind corn process.
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