Lactose-fermenting bacteria are those that consume lactose or other six-carbon sugars and metabolize them through the process of lactic acid fermentation. This process of fermentation releases the energy contained within the bonds of the sugars and produces the byproduct lactic acid. Lactic acid fermentation is a common capability of a wide variety of bacteria.
Many different bacteria engage in lactic acid fermentation. One of the most common bacteria that engage in this type of fermentation is Lactobacillus. Some humans have bacteria in their digestive system that are capable of engaging in lactic acid fermentation. Those who lack such bacteria are called “lactose intolerant” as their body will not digest milk sugars effectively.
Lactic acid fermenting bacteria are used to produce a number of foods, including cheese, yogurt and sauerkraut. When these bacteria are used in such a fashion, the lactic acid produced in the process helps to preserve the food. The lactic acid lowers the pH of the food, which reduces the chances that the food will become spoiled or grow additional bacteria.
Fermentative processes are more primitive forms of metabolism than others, such as oxidative metabolism. Fermentation generally occurs in an oxygen-free environment. Lactic acid fermentation also happens when an animal’s muscles cannot access enough oxygen during heavy exercise.