Nutrient agar:

For 18 to 20 plates:
5g commercial Nutrient Broth (a powder) from Southern Biological
(Or 1g Beef Stock Powder & 2g Peptone)
10g agar powder
500 ml distilled water.
Weigh agar. Add water, stir until dissolved.
Add nutrient broth.
Heat carefully until boiling. Don’t boil over.
Pour into Schott bottles-with the blue cap. Put cap on loosely.
(Or pour into conical flasks and stopper loosely with cotton wool)
Sterilise 20mins at 151 lb/sq in. in an Autoclave or pressure cooker.
Cool a little and pour into sterile petri dishes. using the ‘Aseptic Technique’.
Seal in clear plastic bags, in the fridge. Store upside down; this stops the media from getting wet.
Once inoculated, the plates must be sealed around the edges with Parafilm or wide sticky tape or completely wrapped in cling wrap.
Inoculated plates must not be reopened.
Do not dispose of contaminated plates straight into the bin.
The Health Department insists that THE PLATES MUST BE RE-STRERILISED IN AN AUTOCLAVE OR PRESSURE COOKER BEFORE DISPOSAL.
If this can’t be done then the experiment has to be cancelled.
Place into an oven bag, and re-sterilise as above. They are then safe to throw into the bin.

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