Enzymatic isomerization of glucose to fructose was the process that provided a real alternative to white sugar (sucrose) from cane or beet. The commercial product obtained was high fructose corn syrup (HFCS). Two grades of the syrup have established themselves in the world market, HFCS-42 and HFCS-55. They contain 42% or 55% fructose based on dry substance, respectively. These products account for over a third of the carbohydrate sweetener market in the USA. More than 8 million tons of HFCS are produced annually using glucose isomerase. This represents the largest commercial application of immobilized biocatalysts in industry.