- In this type of respiration the food is broken down into carbon-dioxide and energy in the absence of oxygen. For instance, facultative anaerobes and obligate anaerobes.
- Facultative anaerobes are the organisms that are capable of respiring both in presence as well as absence of oxygen. For example, Escherichia coli.
- Obligate anaerobes are the organisms that are capable of respiring only in absence of oxygen. For example, clostridium tetani.
Anaerobic respiration can further be classified into two types:
Lactic acid fermentation and alcohol fermentation.
- Lactic acid fermentation refers to the metabolic process in which glucose are converted into cellular energy and the metabolite lactate.
- Alcoholic fermentation refers to the biological process in which glucose and other sugars such as fructose, and sucrose are converted into cellular energy, producing ethanol and carbon dioxide.