Submitted to: Corn Utilization Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/9/2004
Publication Date: 6/9/2004
Citation: Lemuz, C.R., Dien, B.S., Tumbleson, M.E., Singh, V., Rausch, K.D. 2004. Ethanol yield determination for dry grind corn processing. Proceedings Corn Utilization and Technology Conference. p. 61. Interpretive Summary:
Technical Abstract: The dry grind corn processing industry has to deal with large amounts of new genetic material every year. There is not a standard method to measure ethanol production rates of each one of these new materials. To optimize the dry grind ethanol process, enzymes, yeast, and corn hybrids are tested for ethanol production. Laboratory techniques such as HPLC and NIR are main tools for these issues, but there are some milestones to overcome. The objective was to develop a standard laboratory assay to measure ethanol yields and make it available to the ethanol industry. The assay was developed using a regular dent corn hybrid with a test weight of 58.4 lb/bu and 1,000 kernel weight of 296 g. Batches of ground corn (25 g) were placed in 125 ml Erlenmeyer flasks fitted with rubber caps and needle vents and each mixed with 75 ml deionized water. Ground corn was liquefied by incubating the slurry at 90°C for 60 min after adding 27 µl of alpha amylase at 6.0 to 6.5 pH. Samples were cooled to 60°C and adjusted to 4.0 to 4.5 pH with 20% v/v HCl. The liquefied corn slurry was saccharified and fermented simultaneously (SSF) by adding 20 µl glucoamylase, 0.4 ml (NH4)SO2, and 5 ml of Saccharomyces inoculum. Fermentations were conducted for 72 hr at 32°C and 150 rpm in a Brunswick incubator shaker. Gravimetric data were used to calculate ethanol production, assuming weight loss resulted from ethanol associated CO2 production. After 72 hr, 2 ml aliquots were removed from the flasks and stored for HPLC analysis. HPLC was used to measure final ethanol and residual glucose concentrations. The procedure gave ethanol yields of 37.4 ± 0.8 g ethanol per 100 g corn for the gravimetric method and 35.1 ± 3.1 g ethanol per 100 g corn for the HPLC method (2.9 ± 0.1 and 2.8 ± 0.2 gal/bu, respectively). For the gravimetric method, ethanol yields were higher; however, differences between gravimetric and HPLC were consistent. The gravimetric method had a smaller variability than the HPLC method. The method provides a reference technique to predict ethanol yields.