To elaborate :
The Cornstarch is treated with alpha-amylase which creates shorter chains of sugars (polysaccharides).
Alpha-amylase is industrially produced by a bacterium. This is purified and then shipped to High Fructose Corn Syrup manufactures.
Using glucoamylase to break down the sugar chains yields the simple sugar glucose.
Unlike alpha-amylase, glucoamylase is produced by Aspergillus, which is a fungus.
Using a fermentation vat you would be notice titchy balls of Aspergillus floating on the top.
The third enzyme used, glucose-isomerase, is particularly costly. This converts glucose to a mixture of about 42 percent fructose and 50-52 percent glucose with some other sugars mixed in.
While alpha-amylase and glucoamylase are added directly to the slurry, expensive glucose-isomerase is packed into columns and the sugar mixture is then passed over it.
Less expensive alpha-amylase and glucoamylase are used only once, glucose-isomerase is reused until it loses most of its activity.
There are two more steps involved. First is a liquid crhomatography step that takes the mixture to 90 percent fructose.
LAstly, this is all back-blended with the original mixture to yield a final concentration of about 55 percent fructose?what the industry calls high fructose corn syrup.