LAB 3 : PREPARATION & STERILIZATION OF CULTURE MEDIA
INTRODUCTION
A growth medium or culture medium is
a liquid or gel designed to support the growth of microorganisms ,cell or
small plants.
There are two major types of growth media: those used for cell culture,
which use specific cell types derived from plants or animals, and microbiological culture, which are used
for growing microorganisms, such as bacteria or yeast. The most common
growth media for microorganisms are nutrient
broths and agar plates, a specialized media are sometimes
required for microorganism and cell culture growth.
figure : agar culture media
Autoclaves are used in
sterilization. The advantage of using an autoclave is that it can reach
temperatures higher than boiling water alone, so it can kill not only bacteria
but also bacterial spores, which tend to be resistant. Autoclaves are used in
laboratories to assure items such as glassware and surgical equipment are
sterile.
Autoclaves are built around
the principal that the boiling point of water increases when it is under
pressure. At 15 pounds of pressure per square inch, the boiling point of water
increases from 100 degrees Celsius to 121 degrees Celsius. At this temperature,
all life forms are killed within 15 minutes.
figure : autoclave machine
OBJECTIVE
To prepare sterile nutrient
agar for culturing microorganisms.
DISCUSSION
The culture media are
prepared by weighing all the broth component as below ;
0.6 g/L “Lab-lemco” powder
(beef extract)
0.4 g/L yeast extract
1.0 g/L peptone (nitrogen
source)
1.0 g/L sodium chloride
3.0 g/L agar powder
figure : agar powder and beef extract
figure : yeast extract
figure : peptone
figure : sodium chloride
Then, put the broth into
Scott bottles and dissolve it with 200 mL of distilled water.
Autoclave sterilization times and
temperatures are dependent on the composition and nature of the items being
autoclaved. Minimum times are usually 15
minutes at 250 F (121 C) or 5 minutes at 270 F (132.2 C). Autoclaves should be set at 250F when
sterilizing . Items to be sterilized are loaded into the autoclave in a manner
so that nothing touches the inside of the chamber. Items to be sterilized
should be placed into the autoclave so that steam can uniformly flow between
items. When the autoclave cycle is complete and the pressure
returns to zero the door may be opened. Before opening the door, wear heat-resistant autoclave gloves. To prevent being scalded from the steam, move
to the opposite side of the door opening.
Open door slowly and once opened, walk away from the direct line of the
steam. After a few minutes, the
autoclave materials can then be removed.
Items will still be very hot for a while. Items should not be used until cool to the touch.
The benefit of autoclaving
is it allows materials to be sterilized
within a relatively short time frame without the use of reagents.
CONCLUSION
REFERENCES
en.wikipedia.org/wiki/Growth_medium
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