Enzyme

From theEthanolSource.com

     Enzymes are catalysts, almost all of which are proteins. They speed up chemical reactions by reducing the amount of activation energy required. As they are catalysts, they are not consumed in the process. Enzymes bind temporarily to one or more of the reactants of the reaction they catalyze. They lower the amount of activation energy needed and thus speed up the reaction. There are over 5000 identified seperate enzymes, each with several different isoforms. For ethanol production, two enzymes are necessary. Additional enzymes can improve yield and alter effects. The main two enzymes we will focus on are alpha-amylase and glucoamylase. However, we will also examine the effects of xylanase, glucanase and cellulase.

Contents 1 Alpha-amylase 2 Glucoamylase 3 Xylanase 4 Glucanase 5 Cellulase

Alpha-amylase

Alpha-amylase is the first enzyme used in the ethanol process. Alpha amylase is used for the liquefaction of grain. It cleaves the bonds on starches, yielding dextrin. While some low temperature amylases exist, most are high temperature.

Glucoamylase

Glucoamylase is the second enzyme used in the ethanol process. It is responsible for the saccharification of grain. Saccharification is the process by which dextrin or other soluable starches are converted to simple sugars. By cleaving more bonds, glucoamylase turns the liquefied starch into glucose.

Xylanase

Xylanase is an additional enzyme that can be used in the ethanol process. Xylanase turns xylan (a type of hemicellulose) into xylose. Xylose can be fermented by some yeasts, or it can be hydrolyzed further to produce glucose. Most grains contain a considerable portion of xylan.

Glucanase

Glucanase is an additional enzyme that can be used in the ethanol process. Glucanase converts glucan into glucose. Glucan exists by a considerable portion in most grains.

Cellulase

Cellulase is an additional enzyme that can be used in the ethanol process. Cellulase converts cellulose into glucose. Cellulose exists by a considerable portion in most grains, and in all plants. Cellulose is what makes up a plant's cell wall. Lignin-free cellulose can be converted directly into glucose. Lignin-free cellulose exists in things like cotton and in newspaper.