Ethanol from Corn: One Route to Gasohol Edward Maslowsky, Jr. Loras College, Dubuque, IA 52001 T h e followine experiment illustrates the preparation of ethanol through the action of enzymes and ;east on whole kernel corn. I t com~lementsdiscussions of organic chemistry, carbohydrates, and enzymes in our one-semester, nonscience major chemistry course. One purpose is to illustrate as closely as practical the method used either industrially or on the farm to convert corn into ethanol, while a second is to illustrate distillation. '['here has heen intprest in using ethanol produced through fermentation of corn in gasohol. A bushel of corn can produce 9.8 liters of ethanol and from 17 to I8 pounds of high protein livestock feed.' Frozen corn is chosen over dry corn because the grinding and soaking steps required for dry corn are unnecessary. It is preferred to canned corn since sugar is often added to canned corn and fermentation gives a n unrealistic picture of the amount of ethanol produced from the corn alone. Active dry yeast is available from the grocery store, presents no storage problems, and is easily dissolved when needed. T h e enzymes are also easily and cheaply ohtained.2 T h e experiment uses two 2-hr neriods and is based on a modification of previouslv reported kxperiments.x4 Reagents prepared beforehand using distilled water are a yeast solution (one 7 g package of dry yeast is dissolved in 150 ml of water), buffer solution (15 g of elacial acetic acid and 12.5 e of sodium acetate are dissolved liter of solution), and bacterial Fn enough water t o n-amvlase and amvloalucosidase solutions (for each enzyme, 3 ml of stock solutionare mixed with 100 ml of water). Procedure
During the first week, 100 g of frozen corn kernels are weighed in a 250-ml beaker. (If the taste test is to be used later, then students should either use new glasswareor take special precautions in cleaning the glassware.) This process can be simplified by using a beaker on
752
Journal of Chemical Education
which a mark has been made that indicates the volume equivalent to 100g of corn. The corn is transferred to a 500-ml flask together with 100 ml ofwater and gently boiled for 15 min. If the mixture becomes t w dry, more water is added. After boiling is completed, an additional LOO ml of water is added. and then 10 ml of bacterial a-amvlase solutiun. After ihc,roughl? mixing nnd ua~tingfor 110mi", :I5 ml oi buffer sulutiun, 10 ml of mnylc*lund~sesolutwn, and 10 ml of yeast 90lution are xucuerrivdy added.'l'hr flask I.; then c,,vert.d with a piece of plastic wrap that is secured with a rubber band, and set aside at rcom temperature for a week. The weight of the flask can be compared before and after the week period to observe the change produced by the evolution of CO?. chanee is not unexoected. Also. a - A 7 "e weieht " flask may be prepared according tn the hove proeeduk hut without the two enzymes. Comparing the weight changes produced in the flask with and without the enzymes illustrates the importance of the enzymes. In the flask without the enzymes, but with the yeast, a 2 g weight change is common. During the second week, theliquid is decanted from the mixture and distilled. Depending on the efficiency of the distillation apparatus, the ethanol oroduced mav he combustible. Its odor and taste are noted, and its solubility in xylene is noted. A chemical reaction is illustrated by adding iodine crystals and 6 M sodium hydroxide tn the ethanol to produce the yellow-colored iodoform. Complete experimental details may be obtained hy sending a self-addressed, stamped envelope to the author. ~~~
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' "Corn . . . Alcohol . . . Farm Fuel!," Iowa Corn Promotion Board.
402 West Towers. 1200 35th St.. West Des Moines. IA 50265.
Enzymes were obtained from~arolinaBiokgical~upplyCo.. 2700 Ywk Rd.. Burlington. NC 27215. Witkowski. A,. and Powers, J.. Enzymes. Nature's Catalysts, Novo Laboratories. Inc.. Educational Aids Department. 59 Danbury Road. Wilton. CT 06897. "Production of Alcohol." Novo Laboratwies. Inc., Educational Aids Department, 59 Danbury Road. Wilton, CT 06897.
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