What is Liquefaction and Saccharification?

Liquefaction and saccharification are two very important processes when it comes to the production of biofuels and other industrial processes. Both of these processes play a crucial role in breaking down complex organic materials into simpler forms, but they differ in their approach and end products. Liquefaction is the process of breaking down starch granules into a viscous slurry of shorter chain dextrins (partially broken-down starches). Saccharification is the process of converting dextrins into simple fermentable sugars (primarily glucose).

How are they used in an Ethanol Plant?

The liquefaction process first begins when the feedstock becomes ground which exposes starches. These starches make it easier for enzyme action to occur. Water and other chemicals (like urea or ammonia) are then added to form a slurry. Next, the newly formed slurry is heated to (85 to 105 C), which breaks open the starch granules. Thus, when the starch granules open, they release their starch molecules. Lastly, a thermostable enzyme known as alpha-amylase is added to break down the gelatinized starch into short-chain dextrins. This reduces the viscosity of the slurry, hence this where the term liquefaction comes from.

The saccharification process begins quickly after liquefaction. The mash that was produced is then cooled to around 55-60 C, which is the optimal temperature for the next enzyme. That enzyme is typically glucoamylase which is added to convert the dextrins into glucose by breaking down the glycosidic bonds. This conversion can last up to seven hours long. The conversion can also occur in a separate tank or may continue during fermentation (this is called simultaneous saccharification and fermentation.)

Both processes are needed to produce ethanol during the fermentation process. The dextrins from the feedstock are used to create glucose. Then, the glucose is used to create ethanol (via yeast) during the fermentation process.