Single celled organism - is a fungus!
- cell membrane
- cell wall
- nucleus containing DNA
Aerobic and Anaerobic Respiration of Yeast
Yeast can respire with or without oxygen:
yeast + oxygen --> carbon dioxide + water
- Necessary for yeast to grow and produce --> Produce more energy
Anaerobic Respiration (Known as Fermentation)
yeast --> carbon dioxide + ethanol (alcohol)
Beer and Wine Making
Carbohydrates are used in the making of beer and wine = enerygy source for the yeast --> respiration
- Malting process - starch in barley grains broken down into sugar solution by enzymes (carbohydrase?) in germinating grains.
- Sugar solution extracted and fermented.
- Hops added to give flavour.
- Use the natural sugars on the fruit as enerfy source for yeast.
- Any fruit or vegetable can be used!
NB: The yeast will be poisoned if the concentration of ethanol exceeds 14%
Yoghurt and Cheese Making
- Starter bacteria added to warm milk
- Bacteria ferments milk sugar -Lactose- to produce lactic acid.
- Lactic acid causes the milk to clot and solidify to yoghurt.
- Fruits and flavours can be added to give the yoghurt its taste.
- Starter bacteria added to warm milk
- Bacteria produces more lacic acid (than in yoghurt) and produces solid curds.
- Curds are seperated from whey. (Whey can be used as animal feed)
- Enzymes are added to speed up seperation process.
- Mould and bacteria are added to give flavour.
- The cheese is left to ripen. (The ripening time depends on the cheese being made)
Growing Microorganisms on an Industrial Scale
Microorganisms are grown in large vessels called fermenters.
To control conditions, industrial fermenters have:
- Air Supply - sterilised air is provided for the microorganisms to respire aerobically.
- Stirrer - the content of the fermenter is stirred to provide an equal distribution of heat and nutrients for the microorganisms.
- Water-Cooled Jacket - removes excess heat produced from the respiring microorganisms. Cold air is constantly pumped into the jacket.
- Measuring instruments - moniter factors e.g pH, tempereture, so that changes are made accordingly.
Phases of Bacterial Growth
(sorry couldn't insert the picture :( )
1) Lag Phase - the bacteria is starting to grow.
2) Exponential Phase - the bacteria is growing, doubling every twenty minutes.
3) Stationary Phase - growth slows and eventually stops.
4) Death Phase - the bacteria is dying faster than it is reproducing and doubling.
Conditions that may change the rate of growth
1) Food used up
2) Metabolism of bacteria causes rise in heat
3) Oxygen levels (respiration) falls
4) CO2 levels rise - change in pH
5) Waste products build up - poison bacteria
- Penicillin is grown from the mould Penicillim Notatum
- Was discovered by Alexander Fleming
- It was further developed and mass production method was developed by Howard Florey and Ernst Chain
- A mould found on a melon was seen to have 200 times the yield of penicillin than that found by Fleming.
- The antibiotic is made by growing the mould (Penicillium) in a fermenter.
- A sterilised medium of sugar, amino acids, mineral salts and other nutrients is added.
- It is made by soaking corn in water.
- The mould only starts producing the antibiotic after it had used up its nutrients (lag phase is about 40 hours).
- The mould produces the antibiotic in aerobic respiration --> oxygen is needed.
To get the maximum yield of Penicillin:
- In the first 40 hours, the mould is provided with enough food to grow.
- Then, the supplies are limited so that the penicillin is produced.
- Next 140 hours, the brith is removed regularly and small amounts of nutrients are added.
- The is gives us the maximum yield of the antibiotic
- It is then extracted and purified to be used as medicine
The fungus Fusarium is ued to make mycoprotein.
Mycoprotein - protein made from fungus
- Grows and reproduces every 5 hours on cheep sugary syrup (made from waste carbohydrates)
- Needs aerbic respiration
- Fungal biomass is harvested, purified and flavours are added.
Can be used as a meat alternative:
- High in protein, and low in fat.
- High in fibre.
- Low in calories
- Is a flammable gas made when bacteria breaks down plant and animal waste in anaerobic conditions
- It is mainly methane but composition depends on waste added and bacteria present.
- Plant and animal waste contain carbohydrates --> potentially enormous energy resources.
Bacteria in biogas works best at 30 degrees. Best suited to hot countries.
Reaction is exothermic. If heat is added at the beginning and generator is insulated --> can work anywhere.
Waste from the generator can be used as fertiliser.
On a small scale, biogas generators can supply enough energy to supply a family, a farm or even a small villiage.
- Main materials: waste vegetables, animal dung, human waste.
- Excellent Fertiliser
- Poor Quality biogas
- Religious and culture taboos against using human waste
- Cow and buffalo dung used
- Less Fertiliser
- Excellent Quality Biogas
Ethanol as a fuel
Sugar Cane or Maize used.
- If the sugar rich products of cane and maize fermented anaerobically --> broken down incompletely --> ethanol produced and extracted by distillation.
Sugar Cane -----------------> Ethanol
Maize ---------------------------.>Sugar--------------------> Ethanol
(Carbohydrase = starch --.> sugar) (Fermentation)
Advantages and Diadvantages of Ethanol as a Fuel
- no toxic or greenhouse gases.
- Can mix with conventional fuel -- reduces pollution a little
- carbon neutral -- no overall increase in carbon dioxide levels in the atmosphere.
- Takes a lot of plant material --> limited to countries with enough space and suitable climate to grow lots of plant material.
- Methods of ethanol productions leaves large quantities of unused cellulose from plant material --> could find way of using it in the future.
- When oil prices drop, can't subsidise with ethanol, still to expensive.
Advantages and Disadvantages of Floating Drum biog
Used for small, medium family sized farms
- Easy to construct
- Easy to operate
- Steady gas pressure produced
- Reliable, well-tried tecnology
- Metal gas holder relatively expensive.
- Metal gas holder may rust.
Advantages and Disadvantages of Fixed Drum biogas
- Low initial cost
- long useful life - no moving/rusting parts
- well insulated
- sealing of gas holder not always tight
- gas pressure fluctuates