Modified Citric Acid Cycle Found in Anaerobic Bacteria to Produce Fumarate in Large Quantities

Posted on May 17, 2023 • 2 minutes • 287 words

Researchers at the University of Nairobi have discovered a modified citric acid cycle in certain anaerobic bacteria that allows for the production of fumarate in large quantities. The citric acid cycle, also known as the Krebs cycle, is a fundamental metabolic pathway utilized by organisms to generate energy through the oxidation of acetyl-CoA. However, under anaerobic conditions, the cycle is unable to proceed normally due to a lack of oxygen as the final electron acceptor. Despite this limitation, the newly discovered pathway found in bacteria such as Desulfovibrio africanus can bypass this issue and produce fumarate, an important molecule with industrial applications.

The modified pathway differs from the standard citric acid cycle in several ways, including the use of different enzymes and substrates. In the standard cycle, the breakdown of citrate produces isocitrate, which is then oxidized into alpha-ketoglutarate, producing NADH and CO2 along the way. However, in bacteria with the modified pathway, citrate is broken down into acetate and pyruvate using citrate lyase, which is then converted into malate and fumarate using fumarate reductase. This conversion produces a net gain of ATP and fumarate, which can be used in various industrial processes such as food preservatives, pharmaceuticals, and as a precursor to the production of succinate.

The discovery of this modified citric acid cycle opens up new possibilities for industrial biotechnology, as it allows for renewable production of fumarate from inexpensive substrates such as glucose. Additionally, this research sheds light on the diversity of metabolic pathways found in different organisms, and may help explain how certain bacteria are able to thrive in anaerobic environments. Further studies are needed to understand the regulation and evolution of this pathway, and to potentially engineer it to increase fumarate production.