Conference Dates

March 8-13, 2009


In a conventional dry grind process, corn is ground and mixed with water to produce slurry. The slurry is cooked; starch in the slurry is liquefied, simultaneously saccharified and fermented to produce ethanol. Typical solids during slurry preparation range from 30 to 34%. Higher solids result in higher ethanol concentration. High final ethanol concentration improves plant profitability by increasing plant capacity and improving plant efficiency. Corn solids higher than 34% are not used in dry grind corn process due to high mash viscosity (after cooking), increase in sugar concentration during fermentation (substrate yeast inhibition) and high final ethanol concentration (product yeast inhibition). Two new technologies have been developed which can be combined to reduce mash viscosity, maintain low sugar and ethanol concentration during fermentation and improve plant productivity. These technologies are: granular starch hydrolyzing enzymes and vacuum stripping of ethanol. Simultaneous liquefaction, saccharification, fermentation and distillation (SLSFD) can be conducted in one step with these two technologies and corn slurry solids higher than 34% can be used. In this study combination of granular starch hydrolyzing enzyme and vacuum stripping were evaluated for ethanol production with 40% slurry solids. Results were compared with conventional process using 40% slurry solids. The SLSFD process fermented slurry with negligible residual glucose content. In the conventional process residual sugar in beer started increasing at 20 hr and final residual sugar concentration of 5% (w/v) was observed. Amount of ethanol production and ethanol productivity of the SLSFD process was 20 to 40% higher compared to the conventional process.