The enzyme, Xylose isomerase, is used to turn glucose to fructose in the high fructose corn syrup creation process; what you find out is that it requires cobalt ions to work.
Cobalt is a metal, heavier than iron, that is added to the isomerase to catalyze the process. In very small amounts, cobalt is good for your body, being part of what makes up vitamin B12, but such small amounts are regularly found in the air, water and food you eat.
Adding it to food is relatively untested.
Very little research has been done on the health effects of excessive cobalt on humans, but much of what research has been done is recorded by the Agency for Toxic Substances and Disease Registry, an agency of the U.S. Department of Health and Human Services, though, admittedly most research on the health effects of cobalt has been done on non-human animals.
"Studies in animals suggest that exposure to high amounts of nonradioactive cobalt during pregnancy might affect the health of the developing fetus."
"The International Agency for Research on Cancer (IARC) has determined that cobalt is possibly carcinogenic to humans."
"Short-term exposure of rats to high levels of cobalt in the food or drinking water results in effects on the blood, liver, kidneys, and heart. Longer-term exposure of rats, mice, and guinea pigs to lower levels of cobalt in the food or drinking water results in effects on the same tissues (heart, liver, kidneys, and blood) as well as the testes, and also causes effects on behavior. Sores were seen on the skin of guinea pigs following skin contact with cobalt for 18 days."
According to Kent and Riegel's Handbook of Industrial Chemistry and Biotechnology, Chapter 31, on high fructose corn syrup industrial enzymes: "cobalt ions remaining in the spent fermentation medium constitute a serious environmental hazard," yet, everywhere you see Xylose isomerase being used, cobalt ions will be present.
Cobalt is just one of the dangers of high fructose corn syrup, as Dr. Mark Hyman explains in the second video below. Fatty liver disease, mercury and other chemicals, both known and unknown, pervade this sweetener.
Dr. Michael McCabe explains effects of cobalt toxicity.
Dr. Mark Hyman explains the severity of the high fructose corn syrup epidemic.
http://www.atsdr.cdc.gov/phs/phs.asp?id=371&tid=64
http://www.ebi.ac.uk/interpro/entry/IPR001998
http://www.lenntech.com/periodic/elements/co.htm