Lab Report 3 by Ooi Sin Ying

Name           : Ooi Sin Ying
No. Matrice : 111410

Introduction:
Culture media are available commercially as powders; the require only addition of water. Nutrient medium is a general preparation for culturing microorganisms which are not nutritionally fastidious.
The broth contains:
 - 3.0 g/L "Lab-lemco" powder (a beef extract)
 - 2.0 g/L yeast extract
 - 5.0 g/L peptone （a nitrogen source)
 - 5.0 g/L sodium chloride
 - 15.0 g/L agar powder
The agar has the same composition, except that it contains 15g/L agar.
The final pH of both media is 7.4.
Autoclaving is a process that use moist heat and pressure so that all parts of the material to be sterilized reach 121ºC for 15 minutes. An autoclave is, in essence, a large pressure cooker; a chamber which may be sealed off against surrounding air. Materials for sterilization are placed in the chamber, the door is sealed, and pressurized steam is forced into the chamber. The incoming steam displaces cooler air through an exhaust valve; this valve closes when the cell cooler air has been vented.
Steam is continually forced into the chamber until the pressure reaches 103kPa above atmospheric pressure; at sea level, this pushes the temperature in the chamber to 121ºC. The high pressure prevent solutions from boiling over at this temperature. Larger volumes require longer than 15 minutes to heat up to 121ºC throughout. After sterilization, the steam pressure is slowly decreased to atmospheric pressure. The sterilized objects can then be removed.

Objective :
To prepare sterile nutrient agar for culturing microorganism

Dicussion :
1. Preparation of nutrient medium.
 - Weigh appropriate amount of broth (with agar) powder into Scott bottles and dissolve with 200mL
   of distilled water. Mix well.
 - Loosely recap the bottles and set aside for sterilization.
 - Sterilized all media at 121ºC for 15 minutes.
 - After autoclaving, remove the media. Allow the broth preparation to cool then tighten the cap of
   each bottle.

2. Principle od autoclave
 - most effective and most efficient means of sterilization.
 - Higher temperature ensure more rapid killing.
 - The standard temperature and pressure of autoclave is 121ºC and 15psi.
 - Autoclave operates by using steam under pressure as a sterilizing agent.
 - High pressures enable steam to reach high temperature which increase heat content and killing
    power.
 - Ideal for sterilizing biohazardous waste, surginal dressing, glassware, microbiologic media, liquids.
 - Plastics and certain medical instrument such as fibre-optic endoscopes cannot withstand
    autoclaving.
 - Materials with bioactive compounds cannot be autoclaved.

3.Principle of laminar flow
 - Physical containment devices that acts as primary barriers to protect  from worker-generated or
   environmental sources of contamination and protect the laboratory worker and laboratory
   environment from expose to infectious or other hazardous materials that are present within the
   hood.
 - Two types of laminar flow :
   (a) Horinzontal laminar flow
   (b) Biological safety cabinet
 - Both use a high-efficiency particulate air (HEPA) filter and blowers that generate a non-mixing
   stream of air.
 - Horizontal laminar flow provide a near-sterile environment for clean handling of non hazardous
    material such as sterile media or equipments.
 - Because of the flow of air within the hood directs back to the user and the room, horizontal flow
   hoods are never to be used with infectious agents or toxic chemicals.
 - Flame sterilization should be minimized in laminar flow as the turbulence generated by the flame
   can disturb the sterile air stream.
 - Turn on the blower and UV light without work for about 60 mins before use and after used.


Conclusion :
The nutrient medium is prepared sucessfully.
Autoclaving is a most effective and most efficient means of sterilization.
Laminar cabinet can provide a contamination free condition during experiment.

Reference :
1.http://en.wikipedia.org/wiki/Autoclave
2.http://wiki.answers.com/Q/The_principle_involved_in_the_operation_of_autoclave
3.http://www.globalrph.com/aseptic.htm
4.http://wiki.answers.com/Q/What_is_the_principle_of_Laminar_air_flow