Yes, humans have been using cells as factories for millennia—especially for the production of cheese, yogurt, beer, and wine—all of which relies on the ability of individual cells to produce specific products, such as lactic acid and ethanol. More recently, scientists have been able to manipulate cell genes, so that cells will produce substances that have little relation to their normal function. Examples of products from bioengineered cell factories include the production of human insulin to treat diabetics and Factor VIII (a naturally produced clotting factor in humans) for hemophiliacs.
A woman enjoys a frozen yogurt treat. Yogurt is an example of a fermented food. It is made when lactose in milk is fermented through bacterial action. These are good bacteria, though, and are helpful to digestion.