Metabolismo microbiano 05. Quimioorganotrofos fermentadores

Summary

This video explains the metabolism of chemoorganotrophic fermenting microorganisms, focusing on the energy extraction from chemical reactions without external electron acceptors. It contrasts fermentation with respiration, detailing the lack of the electron transport chain and the low ATP yield in fermentation. It covers various fermentation pathways like lactic and alcoholic fermentation, highlighting different microorganisms like Lactobacillus and Saccharomyces cerevisiae, as well as the industrial importance of fermentation products like yogurt, wine, and ethanol. The video also touches on other fermentative processes and their relevance to industry.

Takeaways

• 😀 Chemorganotrophic microorganisms obtain energy from chemical reactions and, as fermenters, rely on organic compounds as electron donors.
• 😀 Fermentative metabolism does not involve an electron acceptor, and while oxygen may be present, it is not necessary for fermentation.
• 😀 Fermentation is an energetically inefficient process, producing little ATP and making it less energy-efficient than respiratory metabolism.
• 😀 In respiration, glucose is converted into pyruvate through glycolysis, and later into acetyl-CoA, which enters the Krebs cycle for further energy production.
• 😀 The electron transport chain is a key component of respiration, where electrons are transferred to an electron acceptor, generating proton gradients and ATP.
• 😀 In the absence of an electron acceptor, microorganisms must switch to fermentative metabolism, which does not involve the electron transport chain or proton pumping.
• 😀 The Krebs cycle is often disrupted in fermentative metabolism to avoid excessive production of reduced pyridine nucleotides, which could halt the metabolism.
• 😀 Some reactions in the Krebs cycle may be reversed in fermentation to support necessary biosynthesis and maintain the balance of intermediates.
• 😀 Fermentative microorganisms primarily oxidize sugars, but other compounds like amino acids, organic acids, purines, and pyrimidines can also be fermented.
• 😀 Examples of fermentation products include lactic acid in lactic acid fermentation, and ethanol and CO2 in alcoholic fermentation, with key microorganisms like Lactobacillus and Saccharomyces cerevisiae playing important roles in these processes.

Q & A

What are chemotrophic microorganisms and how do they obtain energy?

Chemotrophic microorganisms obtain energy from chemical reactions. Specifically, chemorganotrophs use organic compounds as electron donors for their energy production.

What distinguishes fermentative metabolism from respiratory metabolism?

Fermentative metabolism does not require an electron acceptor and does not involve oxygen, unlike respiratory metabolism which uses an electron transport chain and oxygen as the final electron acceptor.

What is the ATP yield in fermentation compared to respiration?

Fermentation yields very little ATP, making it an energetically inefficient process compared to respiration, which generates much more ATP through the electron transport chain.

What substrates are commonly used in microbial fermentation?

The most common substrates for microbial fermentation are sugars, such as glucose, although amino acids, organic acids, purines, and pyrimidines can also be fermented.

How is glucose processed in respiration and fermentation?

In respiration, glucose is converted into pyruvate through glycolysis and further metabolized in the Krebs cycle and electron transport chain. In fermentation, glucose is converted to pyruvate and then reduced to various fermentation products, with no involvement of the electron transport chain.

What role does the Krebs cycle play in fermentation?

In fermentation, the Krebs cycle is disrupted to prevent excess reduction power accumulation. Certain reactions of the cycle may proceed in reverse to maintain necessary metabolite production for biosynthesis.

Why is the electron transport chain absent in fermentation?

The absence of the electron transport chain in fermentation is due to the lack of an external electron acceptor, which means electrons cannot be transferred through the chain to generate energy via proton pumping.

What is the main product of homolactic fermentation?

In homolactic fermentation, the main product is lactic acid, produced from pyruvate by the enzyme lactate dehydrogenase using the reducing power from NADH.

What is the role of Saccharomyces cerevisiae in industrial fermentation?

Saccharomyces cerevisiae, a type of yeast, is key in industrial fermentation processes like wine, beer, and bread production, where it ferments glucose into ethanol and CO2 in the absence of oxygen.

How do various bacteria contribute to different fermentation types?

Various bacteria perform different types of fermentation, such as lactic acid fermentation by Lactobacillus species, alcoholic fermentation by yeasts like Saccharomyces cerevisiae, and propionate production by Propionibacterium species.