Problems and profit with

waste

Standard Grade Biology

Biotechnology

Learning Outcomes

• Describe some examples of the

damage caused to the environment

by disposal of untreated sewage.

• Give examples of diseases which may

be spread by untreated sewage.

Untreated Sewage

• Untreated sewage contains

– Organic material

– Mineral salts

– Bacteria

• Some of these can cause disease

• Untreated sewage can have biological

and chemical effects on a river

– Biosphere revision / indicators of pollution

Effect of untreated sewage on

a river

• Complete the diagram with labels

untreated

sewage

bacteria release

nitrates and

phosphates

anaerobic

bacteria releases

methane and

ammonia gases

foul smelling

gases and rotting

material float to

surface

animals die from

lack of oxygen

bacteria respire

using up the

oxygen

algal bloom

(forms a thick

mat)

bacteria feed on

raw sewage

Effect of untreated sewage on a river

Water-borne diseases

• Untreated sewage contains micro-

organisms which can cause disease

– Dysentery

– Typhoid

– Cholera

• Disease is prevented by keeping

sewage separate from drinking water.

Risk of water-borne diseases

• Contamination of drinking water may

occur after

– Earthquakes (pipes fracture)

– Flooding

• Boiling water reduces risk of

contamination

Learning Outcomes

• Describe the principal precautions to be taken during laboratory work with microorganisms.

• Explain the precautions which are taken during manufacturing processes with reference to resistant fungal and bacterial spores.

• Explain the importance of such precautions in biotechnological processes whenever relevant.

Airborne disease

• The air contains

– Dust

– Fungal spores

– Bacteria (and

spores)

Sterile Techniques

• Surfaces are wiped with disinfectant

• Glassware is treated in an autoclave

• Agar plates are prepared to ensure agar is

sterile at the start of the experiment

Culturing microorganisms

• Sterile techniques are used to avoid

contamination with unwanted microbes

Preparing a bacterial culture

Summary of precautions

Resistant Spores

• Bacterial cells protect themselves from

unfavourable conditions by forming

endospores.

• Endospores are resistant to

– Extreme temperatures

– Drying out

– pH changes

– disinfectants

Sterile technique summary

• Write out each technique and write

out why each stage is necessary

– Heating glassware in an autoclave

– Holding lid over open petri dish

– Flaming wire loop

– Flaming the mouth of the culture tube

– Applying tape to the plates

Learning Outcomes

• Describe the part played by bacteria

in the process of decay and recycling

of carbon and nitrogen. Explain the

process of decay in terms of the

energy requirements of micro-

organisms.

Decay

• Decomposers are

– Bacteria

– Fungi

• They decompose

organic substances

in order to obtain

the energy and

materials they need

to survive.

Nutrient cycling

Nutrients in environment

decomposers

consumers

producers decomposition

Fossil fuels

Coal, oil, gas, peat

Combustion

(burning)

Carbon dioxide In the air (CO2)

photosynthesis

respiration

Carbon compounds

in plants

Carbon

compounds

in animals

decay

feeding

The carbon cycle

saprophytes

• Organisms which obtain it’s food from

dead or decaying organic matter.

• Enzymes are secreted onto the food

for external digestion before being

absorbed.

• Mineral salts present in the organic

matter are released into the soil and

are recycled.

Nitrogen Cycle

The Nitrogen Cycle

• Plants and animals need nitrogen to make proteins.

• Nitrogen gas is unreactive and can not be used by living things

• Nitrogen gas must be changed to nitrates before it can be used by plants.

• Animals then eat plants

The Nitrogen Cycle

Nitrogen gas in air (N2)

Nitrates in soil (NO3)

Proteins in Plants Proteins in animals

Dead bodies or

waste material

Ammonium compounds (NH4)

Nitrites in soil (NO2-)

The nitrogen cycle

Nitrogen gas in the air

Nitrogen fixation

Nitrates in soil

Nitrogen fixing

bacteria in the

soil

Nitrogen fixing

bacteria in

root nodules

Nitrifying bacteria

Decay bacteria break

down proteins and

release ammonia

Plant protein Animal protein

Animal wastes

Denitrifying bacteria

Nitrogen fixation

• Making nitrates from the nitrogen gas

in the air

• Nitrogen-fixing bacteria (Rhizobium)

found in the soil and in the root

nodules of leguminous plants, such as

peas, beans and clover

Nitrogen Fixation

Feeding

Decay

• Nitrogen compounds in living things

are returned to the soil as ammonium

compounds through: – excretion and egestion by animals

– the breakdown of dead plants and animals by saprophytic

(decay) bacteria

Nitrifying bacteria

• Change ammonium compounds to

nitrates

Ammonium compounds Nitrosomonas

Nitrites Nitrobacter

Nitrates

decay

decay

Denitrifying bacteria

• Denitrifying bacteria (Pseudomonas

denitrificans) live in water logged soils

(anaerobic conditions)

• They change nitrates back into

nitrogen gas.

denitrification

The bacteria

• The nitrogen cycle involves four different types of bacteria – Saprophytic bacteria

– Nitrifying – Nitrosomonas and Nitrobacter

– Denitrifying – Pseudomonas denitrificans

– Nitrogen-fixing - Rhizobium

• In an exam, you will need to be able to describe the roles of these bacteria

Leaching

• Some nitrates may be washed out of

the soil by rainwater, this is called

leaching.

• Leaching can lead to the

eutrophication of lakes

Decay Summary

• Decay is the breakdown of dead

organisms and waste by microbes

(bacteria and fungi)

• Allows the recycling of nutrients

• Decaying material provides a source

of energy for decomposers

Carbon Cycle Summary

CO2 in air

C Compounds

in plants

C Compounds

in animals

C Compounds

in dead

organisms

Fossils

photosynthesis

respiration

respiration

Respiration by decomposers

Burning of fossil fuels

feeding

Nitrogen Cycle

Key Microbial Processes • Nitrogen Fixation

– Bacteria in root nodules convert nitrogen to nitrate

• Decay – Decomposers (bacteria and fungi) breakdown

nitrogen compounds into ammonium compounds

• Nitrification – Bacteria convert ammonium compounds to

nitrites

– Bacteria convert nitrites to nitrates

• Denitrification – Bacteria convert nitrates to nitrogen gas

Learning Outcomes

• State that the main process in the treatment of sewage is its breakdown by the action of decay micro-organisms to products harmless to the environment.

• Explain why complete breakdown of sewage is only possible in aerobic conditions.

• Describe how the oxygen required by micro-organisms can be provided during sewage treatment.

• Explain why a range of microorganisms is needed to break down the range of materials in sewage.

Sewage

• Sewage is organic waste from humans

• Primary treatment of sewage • Screening

• Grit removal

• Primary settlement

• Secondary Treatment – Oxygen is provided to create aerobic

conditions so that bacteria • Grow faster

• Are more efficient

• Breakdown the sewage completely

– Two methods • Biological filtration

– Sewage is sprayed onto stone beds

• Activated sludge process – Compressed air is forced through sewage

Sludge

• The suspended matter in the “purified” sewage settles out as activated sludge

• The liquid is now effluent

• The effluent is released into the river

• The sludge is treated – Methane gas is produced

– Left over solids go to landfill or sea disposal

Why are a range of micro-

organisms needed • To ensure complete breakdown of sewage

into carbon dioxide, water and inorganic substances

• High concentrations of nitrates could lead to an algal bloom in the river – so bacteria are used to remove excess nitrates, phosphates and ammonium compounds.

• The aim of sewage treatment is to reduce the chemical oxygen demand (COD) of the river to the lowest level possible.

Learning outcomes

• Give 2 examples of useful products and the waste materials from which they are gained through the action of micro-organisms and explain the economic importance of this technology.

• Explain the advantages of upgrading waste in terms of increasing its available energy or protein levels.

Upgrading Waste

• Upgrading waste converts waste products to useful products with a higher economical value.

• Upgrading by micro-organisms – High energy source e.g. methane

– Rich protein source e.g. Mycoprotein

• Advantages – Reduces environmental pollution

– Economic saving on waste disposal

Examples

industry Waste

product

Micro-organism

used in upgrading

Useful

product

Cheese

making whey yeast

Protein

(cattle feed)

vitamins

Gas and

oil methanol

Methylophillus

(bacterium)

Protein

(animal

feed)

Potato

crisps starch Fusarium mycoprotein

Learning outcomes

• State that alcohol and methane are

products of fermentation.

• Explain the advantages of deriving fuel

through fermentation rather than from

fossil sources.

Fuels

• Methane – Micro-organisms carry out anaerobic

fermentation on manure producing methane gas

– Gas is used for heat and electricity

• Alcohol – Fermentation of sugar by yeast produces

alcohol – Alcohol is separated from mixture by

distillation

– Used as a fuel

Fuels

• Fuels from sugars (Brazil) – Sugar cane is grown and fermented into

alcohol

– This mixed with petrol produces gasohol which can be used to run cars

• Fermentation of plant material provides a renewable source of fuels

• Fossil fuels are non-renewable resources

Learning Outcomes

• State that under suitable conditions,

micro-organisms can reproduce very

rapidly by asexual means.

• State that micro-organisms may be

harvested to provide protein rich food

for animals or man.

Growth rate of micro-organisms

• A bacterium divides asexually by

dividing into two.

• Suitable conditions

– Optimum pH

– Optimum temperature

– Supply of food and water

• Unlimited growth can occur under

ideal conditions

Growth of

bacteria • Use the data

to plot a line graph of bacterial growth

• Describe the shape of the curve produced

Time of 24-hour

clock

Number of

bacteria

0900 1

0930 2

1000 4

1030 8

1100 16

1130 32

1200 64

1230 128

1300 256

1330 512

1400 1024

Using micro-organisms

• Single-celled protein

– A high percentage of a bacterial cells mass is protein.

– Bacterial cells are grown, harvested and dried to form a powder called single-celled protein (SCP)

– Used to feed chicken and calves

• Single-celled fuels

– Strains of yeast produce a rich supply of oil

– This would be suitable for human consumption