LAB 3 REPORT BY YI LEE

Name: Choong Yi Lee

Matrix number: 111359

LAB 3: PREPARATION AND STERILIZATION OF CULTURE MEDIA

Introduction:

          Culture media are available commercially as powders; they require only the addition of water. Nutrient is a general purpose preparation for culturing microorganisms which are not nutritionally fastidious. The broth contains:

3.0g/L “Lab-lemco” powder (a beef extract)

2.0g/L yeast extract

5.0g/L peptone (a nitrogen source)

5.0g/L sodium chloride

2.0g/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 121°C 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 closes when the cell cooler air has been vented.

        Steam is continually forced into the chamber until the pressure reaches 103kPa above atmospheric pressure; sea level, this pushes the temperature in the chamber to 121°C. The high pressure prevents solutions from boiling over at this temperature. Larger volumes require longer than 15 minutes to heat up to 121°C 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 microorganisms.

Results:

The sample is prepared successfully and is ready for autoclaving.

weighing broth while preparing the culture media

 Discussion:

Autoclaving and it uses :

           An autoclave is an instrument used to sterilize equipment and supplies by subjecting them to high pressure saturated steam at 121 °C for around 15–20 minutes depending on the size of the load and the contents.

           The heat and pressure effectively eliminates bacteria, viruses and other pathogens and these devices are used extensively in laboratories and medical facilities in the preparation of culture media for microbiology and other life sciences applications, to sterilize laboratory glassware, medical instruments and to decontaminate potentially hazardous medical waste before disposal.

An autoclave

Autoclave Operating Procedures
A written sterilization procedure shall be in place for each workplace. This shall include the following:

1. Parameters
• Appropriate parameters for sterilization shall be determined from the testing with spore vials.
• The time it takes to sterilize a load will change depending upon the load density and the sterilization cycle one chooses. Tests have been performed which imitate these various situations. Please follow the established guidelines.
2. Protocol
• Identification of standard treatment containers and proper load placement shall be made.
3. Cleaning
• The autoclave and work areas shall be cleaned after every use and the work area shall be disinfected, as needed.
   

Reference:  

1) http://en.wikipedia.org/wiki/Autoclave

2) http://ezinearticles.com/?The-Many-Uses-of-Autoclave-Instruments&id=3253665

3) http://www.ehs.ufl.edu/Bio/autoclav.htm

4) http://www.bd.com/ds/technicalCenter/inserts/Nutrient_Agar.pdf

Conclusion:

         After autoclaving, the Scott bottles are removed from the autoclave machine and the cap of the bottle is tightened. The bottles are turned over again for a few times so that no agar will solidify at the bottom of the bottle. This is to make sure that the culture agar can be used for the pour-plate in the next laboratory work.