Slides in this set
3.1 Growing Microbes
Microorganisms, on a small scale, are grown on AGAR in PETRI dishes. Agar
contains CARBOHYDRATE as an energy source, but may also contain some
MINERALS, PROTEINS and VITAMINS and supplementary nutrients.…read more
3.1 Growing Microbes
To prepare an uncontaminated culture:
- Petri dishes and the culture medium (agar) must be sterilised before use.
- Inoculating loops, used to transfer the microorganisms, must be sterile first
by passing through a flame.
- The lid of the Petro dish should be help in place with adhesive tape to
prevent any microorganisms getting in or out.
In schools and colleges these cultures should be incubated (stored) at 25DegC.
If grown at higher temperatures, harmful microorganisms (pathogens) are
more like to grow. In industry, higher temperatures are used to promote
Agar, Culture, Sterile, Inoculating, Incubate.…read more
3.2 Food Production using Yeast
Yeast cells have a NUCLEUS, CYTOPLASM and CELL MEMBRANE surrounded by a
- When oxygen is PRESENT, they respire AEROBICALLY and reproduce quickly.
- When oxygen is ABSENT, they respire ANAEROBICALLY and produce ALCOHOL
(ETHANOL), and CARBON DIOXIDE. This is called FERMENTATION.
When beer is brewed, the starch in barley grains is used as the carbohydrate energy
source for the yeast. The start is first broken down into sugars in the barley grains
by enzymes during the germinating process. When these sugars have been
fermented and the process is complete, hops are added to give the beer flavour.
When wine is made, the grapes contain `natural' sugars, which the yeast used as the
KEY WORDS: Aerobic, Anaerobic, Yeast, Fermentation, Germination, Enzymes, Hops.…read more
3.3 Food Production using Bacteria
Bacteria is widely used in the manufacture of different cheeses. They are also
use to make yogurt.
There are 3 stages to making yogurt:
1. Bacteria is added to warm milk.
2. The milk sugar (Lactose) is fermented by the bacteria, producing lactic acid.
3. The lactic acid caused the milk to clot (solidify) and the yogurt is formed.
Lactose, Lactic Acid, Ferment, Clot.…read more
3.4 Large-Scale Microbe Production
Industrial Fermenters are large vessels used to grow microorganisms. The conditions
in the fermenter are very carefully monitered:
- The is as air supply providing oxygen for respiration.
- There is a stirrer used to keep the microorganisms spread out and to make sure
that the temperature is the same in all parts of the vessel.
- There is a water-cooled jacket around the outside, as the respiring microorganisms
release heat and a constant temperature needs to be maintained.
- There are sensors to monitor both pH and temperature.
The fungus FUSARIUM is grown to produce MYCOPROTEIN, a protein-rich food
suitable for vegetarians. Fusarium is grown aerobically on starch and the
Sensors, Fusarium, Mycoprotein.…read more