The fermentation of glucose by yeast is the process of breaking down the glucose into ethanol, carbon dioxide, and water. This process is used in the production of alcoholic beverages such as beer and wine. Yeast are living microbes and will react to the exposure of ultraviolet light like most living creatures will. Prolonged exposure to concentrated ultraviolet light will damage the DNA of the yeast and ultimately kill the yeast cells. The loss of yeast cells will slow down the rate of fermentation. But controlled exposure to small bursts of ultraviolet light can actually be beneficial to the yeast by stimulating the release of hormones to repair any damage done by the light and increase cell reproduction. The increase in the number of yeast cells will speed up the rate of fermentation. So the amount of ultraviolet light used will have a great effect on the rate.