Materials

• Nutrient Agar (Ager 65.2%, Peptones 21.7%, Beef Extract 13%) Carolina Biological Supply Company
• Distilled Water
• Petri Dish

Finally my contamination test is done. I followed this instruction.

4.6g of Nutrient Agar was mixed with 200ml of distilled water and it was autoclaved in a pressure cooker for more than 20 min. The pressure cooker/canner (16-Quart) I purchased from Amazon is probably too big. It took me more than an hour to get 10 psi even though I intended to bring it up to 15 psi. But it worked in the end.

The one petri dish was left uncovered for 30 min inside of running sterile hood and the other one was left uncovered on top of my work area for 30 min.

The sterile hood one on the left came out clean and the work area petri dish on the right had two molds.