Microbes in household products means the tiny living things (mostly bacteria and fungi like yeast) that we use at home every day to make foods such as curd, cheese, bread, dosa and idli batter. NCERT lists five main household microbes: Lactobacillus (curd), Saccharomyces cerevisiae (dough and bread), and Propionibacterium sharmanii (Swiss cheese), while Aspergillus niger (citric acid) and Trichoderma polysporum (medicine) are NOT household microbes. Memory hook: "Curd, Cheese, Chapati-dough at home = Lacto, Propioni, Yeast."
The three NCERT household microbes and what they make: Lactobacillus turns milk into curd (adds vitamin B12), baker's yeast puffs dough with CO2, and Propionibacterium sharmanii makes the large holes in Swiss cheese with CO2.
Your doubts, answered
Which microbes are used in household products according to NCERT?
NCERT names three main household microbes. Lactobacillus (a lactic acid bacterium, LAB) turns milk into curd. Saccharomyces cerevisiae (baker's yeast) ferments dough for bread, idli and dosa. Propionibacterium sharmanii makes the large holes in Swiss cheese. These are the everyday, home-level uses of microbes.
Why is Aspergillus niger NOT counted as a household microbe?
Aspergillus niger is a fungus used to produce citric acid on a large, industrial scale in fermentors, not in your kitchen. So it belongs to industrial products (Section 8.2), not household products (Section 8.1). NEET 2025 tested exactly this point, so keep household and industrial microbes separate.
What is the difference between household and industrial microbial products?
Household products are made at home in small amounts using simple steps, like curd, cheese, dough and toddy. Industrial products are made in very large vessels called fermentors, like antibiotics, citric acid, enzymes and alcoholic beverages. Same idea (using microbes), different scale and place.
Do microbes only cause disease?
No. This is the most common wrong idea. Chapter 7 talks about disease-causing microbes, but Chapter 8 shows several microbes are useful. The same kingdom of tiny organisms gives us curd, cheese, bread, medicines and clean water. Not all microbes are harmful.
Is toddy a household microbial product?
Yes. NCERT gives toddy as a traditional drink of southern India made by fermenting sap from palms. It is a household example of using microbes for fermentation, so remember it along with curd, cheese and dough.
⚠️ The NEET trap ✗ Students tick Aspergillus niger or Trichoderma polysporum as household microbes because both appear in the same chapter. ✓ Household microbes are only Lactobacillus, Saccharomyces cerevisiae and Propionibacterium sharmanii. Aspergillus niger (citric acid) and Trichoderma polysporum (cyclosporin A) are industrial or biocontrol microbes. 🧠 If it is made in a fermentor or a lab, it is NOT a household microbe.
Real NEET questions
NEET 2025
Which of the following microbes is NOT involved in the preparation of household products?
A. Aspergillus niger
B. Lactobacillus
C. Trichoderma polysporum
D. Saccharomyces cerevisiae
E. Propionibacterium sharmanii
A · C and D only
B · C and E only
C · A and B only
D · A and C only ✓
Solution: Lactobacillus (curd), Saccharomyces cerevisiae (bread/dough) and Propionibacterium sharmanii (Swiss cheese) are household-product microbes. Aspergillus niger produces citric acid on an industrial scale and Trichoderma polysporum yields cyclosporin A (a medicine), so both A and C are NOT household microbes.
NEET 2018
Conversion of milk to curd improves its nutritional value by increasing the amount of
A · Vitamin B12 ✓
B · Vitamin A
C · Vitamin D
D · Vitamin E
Solution: When Lactobacillus (LAB) converts milk to curd at home, it raises the vitamin B12 content, improving the nutritional quality. Vitamins A, D and E are not enriched during this fermentation.
Solved Microbes in Human Welfare NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
What does 'microbes in household products' mean for NEET?
It means the microbes we use at home to make everyday foods: curd, cheese, bread, idli/dosa dough and toddy. It is Section 8.1 of the NCERT chapter Microbes in Human Welfare.
Name the microbes used in household products.
Lactobacillus (curd), Saccharomyces cerevisiae or baker's yeast (dough and bread), and Propionibacterium sharmanii (Swiss cheese holes).
Which vitamin increases when milk becomes curd?
Vitamin B12 increases when Lactobacillus converts milk to curd. This is a very common NEET one-liner (asked in NEET 2018).
Why does dough rise or puff up?
Baker's yeast (Saccharomyces cerevisiae) ferments the dough and produces CO2 gas, which makes it puff up and rise. This is used in bread, idli and dosa.
Is this topic important for NEET?
Yes. Microbes in Human Welfare gives several direct fact-based questions every year, and the household microbes list is repeatedly tested, including in NEET 2025.
