Ripening a Cheese and Ruining a Loaf Are the Same Process
Follow the fermentation that makes bread rise and beer ferment, see how moulds ripen cheese and how mushrooms turn straw into protein, then list the spoilage and crop diseases fungi cause.
Why is mould on cheese wanted and mould on bread a disaster?
A wheel of blue cheese has mould growing through it in visible veins, and that mould is the point of the cheese. It is what gives it the flavour people pay for.
A loaf of bread in a damp kitchen grows mould too, and it goes straight into the bin.
The two fungi are close relatives doing exactly the same thing: breaking organic matter down with enzymes and living on what is released. The cheese-maker calls it ripening and the cook calls it spoilage, and there is no difference in the biology at all.
The only real difference is choice. In a cheese the fungus is a particular species, deliberately introduced, kept in controlled conditions and stopped at the right moment. On the bread it arrived by itself, and nobody is controlling anything.
That pattern runs through the whole of this chapter. Fungi are decomposers, and they decompose whatever they land on.
- When we want the breakdown, we get bread that rises, alcohol, ripened cheese, mushrooms and penicillin
- When we do not, we get mouldy food, rotted timber, ruined crops and ringworm
This page covers the second part of the ICSE Class 9 Biology chapter on economic importance: yeast in bakeries and breweries, fungi in cheese processing and mushroom cultivation, and the harmful effects of fungi on food and crops.
A loaf of bread in a damp kitchen grows mould too, and it goes straight into the bin.
The two fungi are close relatives doing exactly the same thing: breaking organic matter down with enzymes and living on what is released. The cheese-maker calls it ripening and the cook calls it spoilage, and there is no difference in the biology at all.
The only real difference is choice. In a cheese the fungus is a particular species, deliberately introduced, kept in controlled conditions and stopped at the right moment. On the bread it arrived by itself, and nobody is controlling anything.
That pattern runs through the whole of this chapter. Fungi are decomposers, and they decompose whatever they land on.
- When we want the breakdown, we get bread that rises, alcohol, ripened cheese, mushrooms and penicillin
- When we do not, we get mouldy food, rotted timber, ruined crops and ringworm
This page covers the second part of the ICSE Class 9 Biology chapter on economic importance: yeast in bakeries and breweries, fungi in cheese processing and mushroom cultivation, and the harmful effects of fungi on food and crops.
How does yeast make dough rise and alcohol appear?
Yeast is a single-celled fungus that respires anaerobically on sugar, producing alcohol and carbon dioxide — and the two products are what bakeries and breweries want.
The process is fermentation, which is anaerobic respiration by yeast:
The glucose is incompletely broken down, as the respiration chapter explained, so only a little energy is released — but the two products are exactly what is wanted.
In a bakery it is the carbon dioxide that matters. Yeast is mixed into the dough along with a little sugar and warm water and left in a warm place. It ferments the sugar, and the carbon dioxide it releases cannot escape from the sticky elastic dough. The bubbles are trapped, and they push the dough up — it rises and becomes light and porous.
During baking the heat kills the yeast, and both the alcohol and the carbon dioxide evaporate away, leaving the holes behind. That is why a slice of bread is full of small cavities and why baked bread contains no alcohol.
The process is called leavening, and it is why leavened bread is soft while an unleavened chapati or puri, made without yeast, is flat and dense.
In a brewery it is the alcohol that matters. Yeast is added to a sugary liquid — the malted barley of beer, or fruit juice for wine — and allowed to ferment. Here the alcohol is the product; the carbon dioxide is allowed to escape, or kept dissolved under pressure to give the drink its fizz.
Other uses of yeast. It is grown deliberately as a source of vitamin B and protein, sold as food yeast; and it is used in the commercial manufacture of ethanol, including ethanol blended into fuel.
Every Indian kitchen that makes idli or dosa has watched this. A batter of rice and urad dal left overnight in a warm place rises, becomes frothy and turns slightly sour by morning. The rising is carbon dioxide from yeasts fermenting in the batter; the souring is lactic acid from bacteria working alongside them. Steam the risen batter and the trapped gas makes an idli soft.
Now notice that the bakery and the brewery run the same reaction and simply keep different halves of it. One traps the gas and drives off the alcohol; the other keeps the alcohol and lets the gas go.
So there is one process and two products, and the industry is decided by which product is collected. That is worth stating in an answer, because it converts two apparently unrelated uses into a single piece of chemistry.
The process is fermentation, which is anaerobic respiration by yeast:
The glucose is incompletely broken down, as the respiration chapter explained, so only a little energy is released — but the two products are exactly what is wanted.
In a bakery it is the carbon dioxide that matters. Yeast is mixed into the dough along with a little sugar and warm water and left in a warm place. It ferments the sugar, and the carbon dioxide it releases cannot escape from the sticky elastic dough. The bubbles are trapped, and they push the dough up — it rises and becomes light and porous.
During baking the heat kills the yeast, and both the alcohol and the carbon dioxide evaporate away, leaving the holes behind. That is why a slice of bread is full of small cavities and why baked bread contains no alcohol.
The process is called leavening, and it is why leavened bread is soft while an unleavened chapati or puri, made without yeast, is flat and dense.
In a brewery it is the alcohol that matters. Yeast is added to a sugary liquid — the malted barley of beer, or fruit juice for wine — and allowed to ferment. Here the alcohol is the product; the carbon dioxide is allowed to escape, or kept dissolved under pressure to give the drink its fizz.
Other uses of yeast. It is grown deliberately as a source of vitamin B and protein, sold as food yeast; and it is used in the commercial manufacture of ethanol, including ethanol blended into fuel.
Every Indian kitchen that makes idli or dosa has watched this. A batter of rice and urad dal left overnight in a warm place rises, becomes frothy and turns slightly sour by morning. The rising is carbon dioxide from yeasts fermenting in the batter; the souring is lactic acid from bacteria working alongside them. Steam the risen batter and the trapped gas makes an idli soft.
Now notice that the bakery and the brewery run the same reaction and simply keep different halves of it. One traps the gas and drives off the alcohol; the other keeps the alcohol and lets the gas go.
So there is one process and two products, and the industry is decided by which product is collected. That is worth stating in an answer, because it converts two apparently unrelated uses into a single piece of chemistry.
How do fungi ripen cheese, and why grow mushrooms at all?
In cheese the fungus develops the flavour; in mushroom farming the fungus is itself the food.
Cheese processing. Milk is first curdled — the protein is set into a solid curd and the watery whey drained off. At that stage the curd is bland.
The curd is then ripened by particular fungi, which are introduced deliberately and allowed to grow under controlled temperature and humidity. Their enzymes break down the fat and the protein of the curd, and the products of that breakdown are what give a cheese its characteristic flavour, smell and texture.
- Penicillium roqueforti produces the blue-green veins and the sharp flavour of blue cheeses
- Penicillium camemberti grows as a soft white rind and ripens the cheese from the outside inwards
The longer the ripening, the stronger the flavour — which is why cheese is sold by age.
Mushroom cultivation. A mushroom is the fruiting body of a fungus — the part that appears above ground, while the main body of fine threads spreads through the material below.
Two kinds are grown commercially in India:
- Agaricus — the button mushroom, grown on prepared compost
- Volvariella — the paddy-straw mushroom, grown on rice straw, which suits a warm climate
Why mushroom growing is valuable.
- Mushrooms are rich in protein and in vitamins, and low in fat and carbohydrate — so they suit a diet that needs protein without much energy
- They are grown on agricultural waste — paddy straw, wheat husk, sugarcane bagasse, cotton waste — material that would otherwise be burnt. So the process turns waste into food
- They need no farmland and no sunlight, and can be grown in sheds, so they do not compete with crops for ground
- The spent compost left afterwards is good manure
- It provides employment and income on a small scale, needing little land and modest capital
Now the warning that belongs with this section. Not every mushroom is edible. Some, such as Amanita, are severely poisonous, and a few of the poisonous kinds closely resemble edible ones — so much so that appearance alone is not a safe guide.
That is why mushrooms are cultivated rather than gathered, and why a wild mushroom should never be eaten on the strength of how it looks. A question asking why mushroom collecting from the wild is discouraged wants exactly this, and "they might be dirty" is not the answer.
One more use worth a line, because it completes the picture from the previous part. Penicillin, the antibiotic, is obtained from the fungus Penicillium — a relative of the cheese-ripening species. So the group that gives us mouldy bread also gives us the antibiotic that treats bacterial infection, and the antibiotic list of the bacteria lesson is incomplete without it.
Cheese processing. Milk is first curdled — the protein is set into a solid curd and the watery whey drained off. At that stage the curd is bland.
The curd is then ripened by particular fungi, which are introduced deliberately and allowed to grow under controlled temperature and humidity. Their enzymes break down the fat and the protein of the curd, and the products of that breakdown are what give a cheese its characteristic flavour, smell and texture.
- Penicillium roqueforti produces the blue-green veins and the sharp flavour of blue cheeses
- Penicillium camemberti grows as a soft white rind and ripens the cheese from the outside inwards
The longer the ripening, the stronger the flavour — which is why cheese is sold by age.
Mushroom cultivation. A mushroom is the fruiting body of a fungus — the part that appears above ground, while the main body of fine threads spreads through the material below.
Two kinds are grown commercially in India:
- Agaricus — the button mushroom, grown on prepared compost
- Volvariella — the paddy-straw mushroom, grown on rice straw, which suits a warm climate
Why mushroom growing is valuable.
- Mushrooms are rich in protein and in vitamins, and low in fat and carbohydrate — so they suit a diet that needs protein without much energy
- They are grown on agricultural waste — paddy straw, wheat husk, sugarcane bagasse, cotton waste — material that would otherwise be burnt. So the process turns waste into food
- They need no farmland and no sunlight, and can be grown in sheds, so they do not compete with crops for ground
- The spent compost left afterwards is good manure
- It provides employment and income on a small scale, needing little land and modest capital
Now the warning that belongs with this section. Not every mushroom is edible. Some, such as Amanita, are severely poisonous, and a few of the poisonous kinds closely resemble edible ones — so much so that appearance alone is not a safe guide.
That is why mushrooms are cultivated rather than gathered, and why a wild mushroom should never be eaten on the strength of how it looks. A question asking why mushroom collecting from the wild is discouraged wants exactly this, and "they might be dirty" is not the answer.
One more use worth a line, because it completes the picture from the previous part. Penicillin, the antibiotic, is obtained from the fungus Penicillium — a relative of the cheese-ripening species. So the group that gives us mouldy bread also gives us the antibiotic that treats bacterial infection, and the antibiotic list of the bacteria lesson is incomplete without it.
What harm do fungi do to food and to crops?
Fungi spoil stored food and produce poisons in it, and they cause many of the most destructive diseases of crops.
Spoilage of food. Moulds grow on bread, chapatis, jam, pickles, fruit, cheese, leather, cloth, books and damp paper, especially during the monsoon when the air is warm and humid. They make the food discoloured, musty and unfit to eat.
Some go further and produce mycotoxins — poisons that remain in the food even after the mould is removed. Aspergillus growing on stored groundnuts and maize produces aflatoxin, which damages the liver and is dangerous in small quantities.
How spoilage is prevented, and each method denies the fungus a requirement:
- Keep the food dry — moulds need moisture above all, which is why grain is dried before storage
- Keep it cool, and refrigerate where possible
- Store in airtight containers, and in a well-ventilated dry place
- Add preservatives, and use salt, sugar, vinegar or oil as the bacteria lesson described
- Discard food that is already mouldy rather than scraping it — the mycotoxin may have spread further than the visible mould
Fungal diseases of crops. These cause very heavy losses, and the standard examples are:
- Rust and smut of wheat
- Late blight of potato
- Blast of rice
- Red rot of sugarcane
- Powdery mildew and downy mildew of grapes and other crops
- Wilt of cotton, pigeon pea and other plants
- Tikka disease of groundnut
How crop disease is controlled.
- Spraying with a fungicide — a copper sulphate and lime mixture is the traditional one
- Sowing disease-resistant varieties
- Treating the seed with a fungicide before sowing, since many fungi travel on the seed
- Crop rotation, so the fungus of one crop finds no host next season
- Destroying infected plants and crop residue rather than leaving them in the field
- Proper drainage, since most of these fungi need damp conditions
Diseases of humans and animals. Ringworm, athlete's foot, dhobi itch and dandruff are all fungal infections of the skin, scalp or nails, and they spread by contact and by sharing clothes, towels and combs.
Destruction of timber and material. Dry rot of wood weakens beams, doors and furniture; fungi also attack books, clothes, leather goods and even the lenses of optical instruments in damp conditions.
Now put the harmful list beside the useful one, because it is the same list. Penicillium ripens a cheese and gives us penicillin; Penicillium also grows on a rotting orange. Aspergillus is used industrially and also poisons groundnuts. The mould on a loaf is doing precisely what the mould in a blue cheese does.
So every method of preventing fungal spoilage is about conditions, not about the organism. Keep it dry and the fungus cannot act; let it get damp and warm and it will, whether the material is a chapati, a leather bag, a wheat crop or a wooden beam.
Which is why the single most effective thing in a monsoon is dryness, and why a grain store, a bookshelf and a cheese cave are three places where humidity is watched for exactly the same reason with three different answers.
Spoilage of food. Moulds grow on bread, chapatis, jam, pickles, fruit, cheese, leather, cloth, books and damp paper, especially during the monsoon when the air is warm and humid. They make the food discoloured, musty and unfit to eat.
Some go further and produce mycotoxins — poisons that remain in the food even after the mould is removed. Aspergillus growing on stored groundnuts and maize produces aflatoxin, which damages the liver and is dangerous in small quantities.
How spoilage is prevented, and each method denies the fungus a requirement:
- Keep the food dry — moulds need moisture above all, which is why grain is dried before storage
- Keep it cool, and refrigerate where possible
- Store in airtight containers, and in a well-ventilated dry place
- Add preservatives, and use salt, sugar, vinegar or oil as the bacteria lesson described
- Discard food that is already mouldy rather than scraping it — the mycotoxin may have spread further than the visible mould
Fungal diseases of crops. These cause very heavy losses, and the standard examples are:
- Rust and smut of wheat
- Late blight of potato
- Blast of rice
- Red rot of sugarcane
- Powdery mildew and downy mildew of grapes and other crops
- Wilt of cotton, pigeon pea and other plants
- Tikka disease of groundnut
How crop disease is controlled.
- Spraying with a fungicide — a copper sulphate and lime mixture is the traditional one
- Sowing disease-resistant varieties
- Treating the seed with a fungicide before sowing, since many fungi travel on the seed
- Crop rotation, so the fungus of one crop finds no host next season
- Destroying infected plants and crop residue rather than leaving them in the field
- Proper drainage, since most of these fungi need damp conditions
Diseases of humans and animals. Ringworm, athlete's foot, dhobi itch and dandruff are all fungal infections of the skin, scalp or nails, and they spread by contact and by sharing clothes, towels and combs.
Destruction of timber and material. Dry rot of wood weakens beams, doors and furniture; fungi also attack books, clothes, leather goods and even the lenses of optical instruments in damp conditions.
Now put the harmful list beside the useful one, because it is the same list. Penicillium ripens a cheese and gives us penicillin; Penicillium also grows on a rotting orange. Aspergillus is used industrially and also poisons groundnuts. The mould on a loaf is doing precisely what the mould in a blue cheese does.
So every method of preventing fungal spoilage is about conditions, not about the organism. Keep it dry and the fungus cannot act; let it get damp and warm and it will, whether the material is a chapati, a leather bag, a wheat crop or a wooden beam.
Which is why the single most effective thing in a monsoon is dryness, and why a grain store, a bookshelf and a cheese cave are three places where humidity is watched for exactly the same reason with three different answers.
Exam tip
Exam tip: name the fungus, the process and the product it gives
Write the fermentation equation and name yeast as the fungus: .
For a bakery, say the CARBON DIOXIDE is trapped in the dough and makes it rise, and that the alcohol and the gas evaporate during baking. Name the process leavening.
For a brewery, say the ALCOHOL is the product wanted.
One reaction, two industries — the difference is which product is collected. Say it; it is worth a mark.
For cheese, say the fungus RIPENS the curd by breaking down fat and protein, developing the flavour, smell and texture. Name Penicillium roqueforti or Penicillium camemberti.
Curdling comes first and ripening second — the fungus does not curdle the milk.
**For mushrooms, name Agaricus** (button, on compost) and Volvariella (paddy straw). Say a mushroom is the fruiting body.
Give at least three reasons for growing mushrooms: rich in protein and vitamins; grown on agricultural waste, turning waste into food; no farmland needed; spent compost is manure; provides employment.
Say that not all mushrooms are edible and name Amanita as poisonous — this is why they are cultivated rather than gathered.
**Penicillin comes from the FUNGUS Penicillium, not from a bacterium.
Name Aspergillus and aflatoxin on groundnuts and maize, and say the toxin survives after the mould is removed.
Learn the crop diseases with their crops: rust and smut of wheat, late blight of potato, blast of rice, red rot of sugarcane, mildew of grapes, tikka of groundnut.
And for prevention, lead with dryness** — moulds need moisture more than anything else.
For a bakery, say the CARBON DIOXIDE is trapped in the dough and makes it rise, and that the alcohol and the gas evaporate during baking. Name the process leavening.
For a brewery, say the ALCOHOL is the product wanted.
One reaction, two industries — the difference is which product is collected. Say it; it is worth a mark.
For cheese, say the fungus RIPENS the curd by breaking down fat and protein, developing the flavour, smell and texture. Name Penicillium roqueforti or Penicillium camemberti.
Curdling comes first and ripening second — the fungus does not curdle the milk.
**For mushrooms, name Agaricus** (button, on compost) and Volvariella (paddy straw). Say a mushroom is the fruiting body.
Give at least three reasons for growing mushrooms: rich in protein and vitamins; grown on agricultural waste, turning waste into food; no farmland needed; spent compost is manure; provides employment.
Say that not all mushrooms are edible and name Amanita as poisonous — this is why they are cultivated rather than gathered.
**Penicillin comes from the FUNGUS Penicillium, not from a bacterium.
Name Aspergillus and aflatoxin on groundnuts and maize, and say the toxin survives after the mould is removed.
Learn the crop diseases with their crops: rust and smut of wheat, late blight of potato, blast of rice, red rot of sugarcane, mildew of grapes, tikka of groundnut.
And for prevention, lead with dryness** — moulds need moisture more than anything else.
Did you know
Why an idli and a loaf of bread rise for the same reason
A loaf of bread and an idli look nothing alike. One is baked in an oven in a Western kitchen, the other steamed in a stack of moulds in an Indian one. One is made of wheat, the other of rice and dal.
Both are soft and full of holes, and both are soft for exactly the same reason: a micro-organism blew bubbles into the mixture and the bubbles were trapped.
In bread the organism is yeast, added deliberately, and the gas is carbon dioxide from fermentation. In idli batter the yeasts are already present on the grain and in the air, and they are left overnight to do the same work while lactic acid bacteria sour the batter alongside them.
Then the mixture is cooked, the gas expands with the heat, the starch and protein set around the bubbles, and the holes are locked in place. Kill the organisms first and you get something quite different: an unleavened chapati, a puri, a flat dense biscuit.
Which explains a few things every cook knows without knowing why. A batter left out on a cold night barely rises, because the yeast is too cold to ferment. A batter left too long goes sour and collapses, because the fermentation has gone on past the useful point. Adding a pinch of sugar speeds it up, because sugar is the substrate. And a batter kept in an airtight container can lift its own lid.
There is a wider point in this. The same reaction turns up in a bakery, a brewery, a vat of curd and an idli pot — and in each case somebody noticed the effect and learnt to control it long before anybody could have written down the equation for it.
The chemistry was being used correctly for a very long time before it was understood, and a good deal of traditional food processing is exactly that: careful control of a micro-organism by people who knew the conditions precisely and the organism not at all.
Both are soft and full of holes, and both are soft for exactly the same reason: a micro-organism blew bubbles into the mixture and the bubbles were trapped.
In bread the organism is yeast, added deliberately, and the gas is carbon dioxide from fermentation. In idli batter the yeasts are already present on the grain and in the air, and they are left overnight to do the same work while lactic acid bacteria sour the batter alongside them.
Then the mixture is cooked, the gas expands with the heat, the starch and protein set around the bubbles, and the holes are locked in place. Kill the organisms first and you get something quite different: an unleavened chapati, a puri, a flat dense biscuit.
Which explains a few things every cook knows without knowing why. A batter left out on a cold night barely rises, because the yeast is too cold to ferment. A batter left too long goes sour and collapses, because the fermentation has gone on past the useful point. Adding a pinch of sugar speeds it up, because sugar is the substrate. And a batter kept in an airtight container can lift its own lid.
There is a wider point in this. The same reaction turns up in a bakery, a brewery, a vat of curd and an idli pot — and in each case somebody noticed the effect and learnt to control it long before anybody could have written down the equation for it.
The chemistry was being used correctly for a very long time before it was understood, and a good deal of traditional food processing is exactly that: careful control of a micro-organism by people who knew the conditions precisely and the organism not at all.
Exam relevance
Why does NEET keep returning to fermentation and fungi?
Because Class 12 has a whole chapter on microbes in human welfare, and almost every industrial fungus on this page appears in it.
This is the foundation for Class 11 Biology Biological Classification and Class 12 Microbes in Human Welfare, examined in NEET. Biological Classification covers Kingdom Fungi properly — the classes Phycomycetes, Ascomycetes, Basidiomycetes and Deuteromycetes, with Penicillium and yeast among the Ascomycetes and Agaricus among the Basidiomycetes. Questions asking which class a named fungus belongs to are standard, so the genera learnt here should be learnt with their class later.
Fermentation is examined as a pathway. Class 11 Respiration in Plants gives the alcoholic fermentation of yeast with the enzymes named — pyruvate decarboxylase and alcohol dehydrogenase — and contrasts it with lactic acid fermentation. The ATP yield of fermentation against aerobic respiration is a recurring calculation in JEE Main and NEET, and the reason it is so low is the incomplete breakdown described in the respiration chapter.
Class 12 covers the industrial products directly. Yeast for bread, beer, wine and ethanol; Penicillium for penicillin; and the other microbial products — citric acid from Aspergillus, statins from Monascus, cyclosporin A from Trichoderma. Match-the-column questions pairing a microbe with its product are among the most predictable NEET items in that chapter, and the fungi on this page are several of the rows.
Cheese is an examined example. Class 12 names the ripening of cheese by Penicillium roqueforti and the role of Lactobacillus in curdling — so the two-stage process described here, curdling then ripening, is what that question tests. Swiss cheese and its large holes from a bacterial gas are the companion example.
Mushroom cultivation appears as an applied topic. Class 12 Strategies for Enhancement in Food Production covers it under single-cell protein and the use of agricultural waste, and the nutritional argument made here — high protein, low fat, grown on waste — is the argument that chapter makes.
Crop disease is examined in plant pathology and in breeding. Class 12 covers disease-resistant varieties as a goal of plant breeding, naming resistance to rust of wheat as an example. The list of fungal crop diseases here is what makes that breeding objective make sense, and biological control with Trichoderma is covered as a biocontrol agent.
Aflatoxin is examined as a food-safety point, and fungal skin diseases — ringworm and athlete's foot — appear in Class 12 Human Health and Disease among the diseases caused by fungi, alongside Candida.
What the questions look like. For board work, expect explain the role of yeast in bakeries and breweries with the equation, describe the use of fungi in cheese processing, give the advantages of mushroom cultivation, state four harmful effects of fungi with examples, and name two fungal diseases of crops with the crop affected. Every answer wants a named fungus. For NEET, expect microbe-to-product matching, the class a fungus belongs to, fermentation pathway questions and biocontrol agents.
How board and competitive emphasis differ. A board paper rewards the named fungus with the process and the product. A competitive paper assumes all three and asks for the class, the enzyme, or which product a less familiar microbe yields.
The single trap that costs the most marks. Attributing penicillin to a bacterium. An antibiotic is defined as a product of a micro-organism, and micro-organisms include fungi — **penicillin comes from Penicillium, a fungus, while streptomycin and tetracycline come from bacteria. The defence is to attach each antibiotic to its source organism when you first learn it**, because the definition of an antibiotic says nothing about which kingdom it came from, and a question that lists four antibiotics and asks which is fungal is testing only that one fact.
This is the foundation for Class 11 Biology Biological Classification and Class 12 Microbes in Human Welfare, examined in NEET. Biological Classification covers Kingdom Fungi properly — the classes Phycomycetes, Ascomycetes, Basidiomycetes and Deuteromycetes, with Penicillium and yeast among the Ascomycetes and Agaricus among the Basidiomycetes. Questions asking which class a named fungus belongs to are standard, so the genera learnt here should be learnt with their class later.
Fermentation is examined as a pathway. Class 11 Respiration in Plants gives the alcoholic fermentation of yeast with the enzymes named — pyruvate decarboxylase and alcohol dehydrogenase — and contrasts it with lactic acid fermentation. The ATP yield of fermentation against aerobic respiration is a recurring calculation in JEE Main and NEET, and the reason it is so low is the incomplete breakdown described in the respiration chapter.
Class 12 covers the industrial products directly. Yeast for bread, beer, wine and ethanol; Penicillium for penicillin; and the other microbial products — citric acid from Aspergillus, statins from Monascus, cyclosporin A from Trichoderma. Match-the-column questions pairing a microbe with its product are among the most predictable NEET items in that chapter, and the fungi on this page are several of the rows.
Cheese is an examined example. Class 12 names the ripening of cheese by Penicillium roqueforti and the role of Lactobacillus in curdling — so the two-stage process described here, curdling then ripening, is what that question tests. Swiss cheese and its large holes from a bacterial gas are the companion example.
Mushroom cultivation appears as an applied topic. Class 12 Strategies for Enhancement in Food Production covers it under single-cell protein and the use of agricultural waste, and the nutritional argument made here — high protein, low fat, grown on waste — is the argument that chapter makes.
Crop disease is examined in plant pathology and in breeding. Class 12 covers disease-resistant varieties as a goal of plant breeding, naming resistance to rust of wheat as an example. The list of fungal crop diseases here is what makes that breeding objective make sense, and biological control with Trichoderma is covered as a biocontrol agent.
Aflatoxin is examined as a food-safety point, and fungal skin diseases — ringworm and athlete's foot — appear in Class 12 Human Health and Disease among the diseases caused by fungi, alongside Candida.
What the questions look like. For board work, expect explain the role of yeast in bakeries and breweries with the equation, describe the use of fungi in cheese processing, give the advantages of mushroom cultivation, state four harmful effects of fungi with examples, and name two fungal diseases of crops with the crop affected. Every answer wants a named fungus. For NEET, expect microbe-to-product matching, the class a fungus belongs to, fermentation pathway questions and biocontrol agents.
How board and competitive emphasis differ. A board paper rewards the named fungus with the process and the product. A competitive paper assumes all three and asks for the class, the enzyme, or which product a less familiar microbe yields.
The single trap that costs the most marks. Attributing penicillin to a bacterium. An antibiotic is defined as a product of a micro-organism, and micro-organisms include fungi — **penicillin comes from Penicillium, a fungus, while streptomycin and tetracycline come from bacteria. The defence is to attach each antibiotic to its source organism when you first learn it**, because the definition of an antibiotic says nothing about which kingdom it came from, and a question that lists four antibiotics and asks which is fungal is testing only that one fact.
Key takeaways
Fungi in industry and the harm they do: quick revision
- Yeast is a single-celled fungus, and fermentation is its anaerobic respiration: .
- Bakery — the carbon dioxide is trapped in the elastic dough and makes it rise; baking kills the yeast and drives off both the alcohol and the gas, leaving the holes. The process is leavening.
- Brewery — the alcohol is the product wanted; the gas escapes or is kept dissolved as fizz.
- One reaction, two industries — the difference is which product is collected.
- Other uses of yeast: a source of vitamin B and protein, and the commercial manufacture of ethanol.
- Idli and dosa batter rises on the same carbon dioxide, with lactic acid bacteria souring it alongside the yeast.
- Cheese — the milk is curdled first, then the curd is ripened by fungi whose enzymes break down its fat and protein, developing the flavour, smell and texture. Penicillium roqueforti gives the blue veins; Penicillium camemberti the soft white rind.
- Mushroom — the fruiting body of a fungus. Agaricus (button) is grown on compost; Volvariella (paddy straw) on rice straw.
- Value of mushroom growing: rich in protein and vitamins and low in fat; grown on agricultural waste, turning waste into food; needs no farmland or sunlight; the spent compost is manure; provides employment on little land.
- Not all mushrooms are edible — Amanita is severely poisonous and some poisonous kinds resemble edible ones, which is why mushrooms are cultivated rather than gathered.
- Penicillin is obtained from the fungus Penicillium.
- Food spoilage — moulds on bread, chapatis, jam, pickles, fruit, leather, cloth and paper, especially in the monsoon. Mycotoxins remain after the mould is removed; Aspergillus on groundnuts and maize produces aflatoxin.
- Prevention — keep food dry above all, keep it cool, use airtight containers and good ventilation, add preservatives, and discard mouldy food rather than scraping it.
- Fungal crop diseases: rust and smut of wheat, late blight of potato, blast of rice, red rot of sugarcane, powdery and downy mildew of grapes, wilt, and tikka of groundnut.
- Control — fungicide spraying (a copper sulphate and lime mixture), resistant varieties, seed treatment, crop rotation, destroying infected plants, and good drainage.
- Human fungal diseases: ringworm, athlete's foot, dhobi itch, dandruff — spread by contact and shared clothing.
- Destruction of material: dry rot of timber, and damage to books, cloth, leather and optical instruments in damp conditions.
- The useful and the harmful fungi are the same organisms. Penicillium ripens cheese, yields penicillin and rots an orange — so every preventive method works on the conditions, and dryness is the most effective of them.
Name any fungus on this page and say both a use and a harm for it — if most of them give you both, you have understood what this chapter is actually about.
- Bakery — the carbon dioxide is trapped in the elastic dough and makes it rise; baking kills the yeast and drives off both the alcohol and the gas, leaving the holes. The process is leavening.
- Brewery — the alcohol is the product wanted; the gas escapes or is kept dissolved as fizz.
- One reaction, two industries — the difference is which product is collected.
- Other uses of yeast: a source of vitamin B and protein, and the commercial manufacture of ethanol.
- Idli and dosa batter rises on the same carbon dioxide, with lactic acid bacteria souring it alongside the yeast.
- Cheese — the milk is curdled first, then the curd is ripened by fungi whose enzymes break down its fat and protein, developing the flavour, smell and texture. Penicillium roqueforti gives the blue veins; Penicillium camemberti the soft white rind.
- Mushroom — the fruiting body of a fungus. Agaricus (button) is grown on compost; Volvariella (paddy straw) on rice straw.
- Value of mushroom growing: rich in protein and vitamins and low in fat; grown on agricultural waste, turning waste into food; needs no farmland or sunlight; the spent compost is manure; provides employment on little land.
- Not all mushrooms are edible — Amanita is severely poisonous and some poisonous kinds resemble edible ones, which is why mushrooms are cultivated rather than gathered.
- Penicillin is obtained from the fungus Penicillium.
- Food spoilage — moulds on bread, chapatis, jam, pickles, fruit, leather, cloth and paper, especially in the monsoon. Mycotoxins remain after the mould is removed; Aspergillus on groundnuts and maize produces aflatoxin.
- Prevention — keep food dry above all, keep it cool, use airtight containers and good ventilation, add preservatives, and discard mouldy food rather than scraping it.
- Fungal crop diseases: rust and smut of wheat, late blight of potato, blast of rice, red rot of sugarcane, powdery and downy mildew of grapes, wilt, and tikka of groundnut.
- Control — fungicide spraying (a copper sulphate and lime mixture), resistant varieties, seed treatment, crop rotation, destroying infected plants, and good drainage.
- Human fungal diseases: ringworm, athlete's foot, dhobi itch, dandruff — spread by contact and shared clothing.
- Destruction of material: dry rot of timber, and damage to books, cloth, leather and optical instruments in damp conditions.
- The useful and the harmful fungi are the same organisms. Penicillium ripens cheese, yields penicillin and rots an orange — so every preventive method works on the conditions, and dryness is the most effective of them.
Name any fungus on this page and say both a use and a harm for it — if most of them give you both, you have understood what this chapter is actually about.