Back to: MICROBIOLOGY 200 LEVEL
Welcome to class!
Hello there, bright mind! I’m truly excited to have you here again. You’ve been learning with so much determination, and I can already tell you’re becoming a microbiology genius. Today, we’re going to look at a very practical and fascinating topic—Fermentation, especially the types you’ve definitely seen in everyday Nigerian life: lactic acid fermentation, alcoholic fermentation, and mixed acid fermentation. Let’s get right into it in a simple, friendly way.
Fermentation: Lactic Acid, Alcoholic, Mixed Acid Fermentation
What is Fermentation?
Fermentation is a process used by cells—especially microbes—to make energy without using oxygen. When there’s no oxygen, microbes still need to survive and produce ATP (energy). So, they use fermentation to break down sugars like glucose into simpler compounds and release energy in the process.
Fermentation is anaerobic, meaning it doesn’t require oxygen, and it mostly happens in the cytoplasm of microbial cells.
Let’s break down the three major types:
1. Lactic Acid Fermentation
This type of fermentation converts glucose into lactic acid. You’ve seen it happen if you’ve ever left pap (akamu) to ferment or if you’ve tasted nunu (fermented milk).
Microorganisms involved: Lactobacillus, Streptococcus
End product: Lactic acid
Energy produced: 2 ATP per glucose
Lactic acid fermentation also happens in our muscles during intense exercise, when there’s not enough oxygen. That’s why you sometimes feel a burning sensation—that’s lactic acid!
Relatable example: Think of how cassava is turned into fufu or garri—lactic acid bacteria are working there, fermenting the starch and giving it that sour taste and smell.
2. Alcoholic Fermentation
In this type, microbes convert glucose into ethanol (alcohol) and carbon dioxide.
Microorganisms involved: Saccharomyces cerevisiae (yeast)
End products: Ethanol and CO₂
Energy produced: 2 ATP per glucose
This is the process used in brewing pito, palm wine, and even bread-making (the bubbles in dough come from CO₂ gas).
Relatable example: When dough rises before baking agege bread, it’s because of yeast fermentation producing carbon dioxide, which makes it soft and fluffy.
3. Mixed Acid Fermentation
This is a more complex fermentation pathway where glucose is converted into a mix of acids and gases.
Microorganisms involved: Escherichia coli, Salmonella, Shigella
End products: Lactic acid, acetic acid, ethanol, formic acid, and gases like CO₂ and H₂
This type is common in bacteria found in the human gut and some spoiled foods.
If you’ve ever smelt a foul odour from spoilt beans or waste material, chances are mixed acid fermentation is happening there—those microbes are breaking things down with all sorts of by-products.
Why is Fermentation Important?
It helps microbes survive without oxygen.
It allows food preservation and adds flavour (e.g., ogi, iru, yoghurt).
It is used in industries—like baking, brewing, and pharmaceuticals.
It also has medical importance in understanding how some gut bacteria function.
Summary
- Fermentation is the breakdown of sugars without oxygen.
- Lactic acid fermentation produces lactic acid and is used in foods like nunu and ogi.
- Alcoholic fermentation produces ethanol and CO₂, useful in baking and brewing.
- Mixed acid fermentation results in several acids and gases and is common in gut bacteria.
- All three types help microbes produce energy (ATP) when oxygen is not available.
Evaluation
- What is fermentation, and where does it take place in the cell?
- Name one food example for each of the three fermentation types.
- What are the by-products of alcoholic fermentation?
- Which microorganism is commonly used in lactic acid fermentation?
Wow! You’ve done excellently today. Understanding fermentation not only deepens your microbiology knowledge, but it also helps you appreciate the everyday science around you. From the food on your plate to the microbes in your body, you’re learning how life functions. Keep going—you’re capable, smart, and destined for great things. Afrilearn is cheering you on all the way. See you in the next exciting lesson!