Key Difference – Aerobic vs Anaerobic Fermentation
The term Aerobic fermentation is a misnomer since fermentation is anaerobic, i.e., it does not require Oxygen. Thus, aerobic fermentation does not actually refer to a fermentation process; this process refers to the process of cellular respiration. The key difference between aerobic and anaerobic fermentation is that aerobic fermentation uses oxygen whereas anaerobic fermentation does not use oxygen. The further differences will be discussed in this article.
What is Aerobic Fermentation
As mentioned above, the term “Aerobic fermentation” is misnamed because fermentation is an anaerobic process. Simply, this is a process of burning simple sugars to energy in cells; more scientifically, it can be called aerobic respiration.
It can be defined as the process of producing cellular energy in the presence of oxygen. It roughly produces 36 ATP molecules by breaking down foods in the mitochondria. It includes three steps namely glycolysis, citric acid cycle, and electron transport system. It consumes Carbohydrates, Fats, and Proteins; the final products of this process are carbon dioxide and water.
Simplified reaction
C6H12O6 (s) + 6 O2 (g) → 6 CO2 (g) + 6 H2O (l) + heat
ΔG = −2880 kJ per mol of C6H12O6
(-) indicates that reaction can occur spontaneously
Aerobic Respiration Process
1. Glycolysis
It is a metabolic pathway that occurs in the cytosol of cells in living organisms. This can function either in the presence or absence of oxygen. It produces pyruvate in the presence of oxygen. Two ATP molecules are produced as the net energy form.
The overall reaction can be expressed as follows:
Glucose + 2 NAD+ + 2 Pi + 2 ADP → 2 pyruvate + 2 NADH + 2 ATP + 2 H+ + 2 H2O + heat
Pyruvate is oxidized to acetyl-CoA and CO2 by the pyruvate dehydrogenase complex (PDC). It’s located in mitochondria of eukaryotic and cytosol of prokaryotes.
2. Citric Acid Cycle
Citric Acid Cycle is also called Krebs cycle and occurs in the mitochondrial matrix. This is a 8 step process involving different types of enzymes and co-enzymes. The net gain from one glucose molecule is 6 NADH, 2 FADH2, and 2 GTP.
3. Electron Transport System
Electron transport system is also known as oxidative phosphorylation. In eukaryotes, this step occurs in the mitochondrial cristae.
What is Anaerobic Fermentation?
Anaerobic fermentation is a process that causes the breakdown of organic compounds. This process reduces nitrogen to organic acids and ammonia. Carbon from organic compounds is released mainly as methane gas (CH4). A small portion of carbon may be respired as CO2. The decomposition technique occurred here is used in composting. The decomposition occurs as four stages namely: hydrolysis, acidogenesis, acetogenesis, and methanogenesis.
Anaerobic Fermentation Process
1. Hydrolysis
C6H10O4 + 2H2O → C6H12O6 + 2H2
2. Acidogenesis
C6H12O6 ↔ 2CH3CH2OH + 2CO2
C6H12O6 + 2H2 ↔ 2CH3CH2COOH + 2H2O
C6H12O6 → 3CH3COOH
3. Acetogenesis
CH3CH2COO– + 3H2O ↔ CH3COO– + H+ + HCO3– + 3H2
C6H12O6 + 2H2O ↔ 2CH3COOH + 2CO2 + 4H2
CH3CH2OH + 2H2O ↔ CH3COO– + 2H2 +H+
4. Methanogenesis
CO2 + 4H2 → CH4 + 2H2O
2C2H5OH + CO2 → CH4 + 2CH3COOH
CH3COOH → CH4 + CO2
What is the difference between Aerobic and Anaerobic Fermentation?
Characteristics of Aerobic and Anaerobic Fermentation
Oxygen Usage:
Aerobic fermentation: Aerobic fermentation uses oxygen.
Anaerobic fermentation: Anaerobic fermentation does not use oxygen.
ATP Yield:
Aerobic fermentation: Aerobic fermentation yields 38 ATP molecules
Anaerobic fermentation: Anaerobic fermentation does not produce ATP molecules.
Occurrence:
Aerobic fermentation: Aerobic fermentation occur inside living organisms.
Anaerobic fermentation: Anaerobic fermentation occurs outside living organisms.
Microorganism’s Involvement:
Aerobic fermentation: No microorganisms are involved
Anaerobic fermentation: Microorganisms are involved
Temperature:
Aerobic fermentation: An ambient temperature is not required for the process.
Anaerobic fermentation: Ambient temperature is required for the process.
Technique:
Aerobic fermentation: Aerobic fermentation is an energy production method.
Anaerobic fermentation: Anaerobic fermentation is a decomposition method.
Stages:
Aerobic fermentation: Stages include Glycolysis, Krebs cycle, and electron transport system
Anaerobic fermentation: Anaerobic fermentation has no glycolysis or other stages.
CH4 Production:
Aerobic fermentation: Aerobic fermentation does not produce CH4 .
Anaerobic fermentation: Anaerobic fermentation produces CH4.
References:
Cellular respiration [Online]. Available: https://en.wikipedia.org/wiki/Cellular_respiration#Aerobic_respiration [Accessed July 7 2016].
Anaerobic Fermentation [Online]. Available: http://whatcom.wsu.edu/ag/compost/fundamentals/biology_anaerobic.htm 2016].
Anaerobic Digestion Process [Online]. Available: http://www.wtert.eu/default.asp?Menue=13&ShowDok=12 [Accessed July 8 2016].
Image Courtesy:
“CellRespiration” By RegisFrey – Own work (CC BY-SA 3.0) via Commons Wikimedia
“Compost-dirt” By normanack – (CC BY 2.0) via Commons Wikimedia