Characterization of amylose lipid complexes and their effect on the dry grind ethanol process

Authors: BHATIA, GITANSHU - University Of Illinois; JUNEJA, ANKITA - Archer Daniels Midland; Johnston, David; RAUSCH, KENT - University Of Illinois; TUMBLESON, M - University Of Illinois; SINGH, VIJAY - University Of Illinois

Submitted to: Starch/Starke
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2021
Publication Date: 5/29/2021
Citation: Bhatia, G., Juneja, A., Johnston, D., Rausch, K., Tumbleson, M.E., Singh, V. 2021. Characterization of amylose lipid complexes and their effect on the dry grind ethanol process. Starch/Starke. https://doi.org/10.1002/star.202100069.
DOI: https://doi.org/10.1002/star.202100069

Interpretive Summary: An insoluble complex between soluble starch (amylose) and lipids, called AMLs, can form under conditions of high temperature and excess water. These conditions exist in the corn dry grind ethanol process and the formation of AMLs may negatively impact the ethanol yield due to their resistance to enzymatic conversion into the sugars needed for ethanol production. To address this problem, we measured the formation of AMLs under different temperatures, corn concentrations, and enzymes. We found that certain enzymes helped reduce the formation of AMLs and that cooking at higher temperatures (>100 degree C) also reduced their formation. This information will benefit ethanol producers and researchers who are interested in optimization of ethanol production conditions.

Technical Abstract: Amylose lipid complexes (AMLs) are likely to form under high temperature (85 to 105 degree C) and excess water conditions, during liquefaction of ground corn in the dry grind process, due to interaction of gelatinized starch with corn lipids. AMLs are water insoluble and inaccessible to a-amylase action resulting in decreased sugar available for yeast. This reduces the final ethanol yield. In this study, the effect of liquefaction temperature, corn grind size, slurry solids loading and different commercial a-amylases on AML formation was evaluated. AML content was found to decrease in post liquefaction solids (liquefact) as corn grind size was increased, with an observed decrease of 2.46% between ground corn passed through 0.5- and 2.5-mm sieves. Across all solids levels tested, the mean difference in AML content was 0.61% lower at 105 degree C relative to the 85 degree C liquefaction temperature. At 85 degree C, liquefact from all three a-amylases, had similar AML content. However, at 105 degree C liquefaction temperature, enzyme AA2 had the lowest AML production compared to other amylases. Overall, high temperature liquefaction (>100 degree C) had the most predominant effect on reducing AML formation compared to other parameters. Optimizing liquefaction parameters can help reduce AML formation and improve profitability of the dry grind ethanol process.