Homemade Gelatin Plates for Growing Microorganisms

Introduction

In the microbiology laboratory different types of media are used to grow microorganisms. Nutrient agar is typically used in the laboratory, but can be expensive to buy and difficult to make in a home setting. Gelatin plates are able to grow various types of fungi as well as some bacteria. Only microorganisms that utilize the enzyme gelatinase will be able to break down the gelatin as a source of protein. If you choose to grow organisms on the gelatin that can use it as a nutrient source, the gelatin will assume a more liquid consistency after the organisms break it down.

The process of creating gelatin plates is simple and can be completed using materials available at the grocery store. This project is intended for people who have had some experience dealing with microorganisms. Growing microorganisms in your home isnot recommended, it is much safer to grow them in a controlled laboratory.

Supplies

· 1.5 packets of plain gelatin
· 1 cup of water
· 2 teaspoons of sugar
· 4 beef cubes
· 6 Foil muffin cups (these will act as petri plates)
· 6 sandwich bags

Equipment

· Small pot
· Measuring cup and measuring spoons

Time & Cost

This project should take 30 minutes or less, including the time allotted for the mixture to cool in the foil cups. The total cost for the ingredients required was $8.17 and the recipe makes about 6 nutrient gelatin plates.

Potential Hazards

THE STOVE TOP AND PAN WILL BE HOT. Boiling water will be required in this project, so keep an eye on the pan to make sure the water does not boil over and scald your skin. When pouring the mixture into the foil cups, make sure you do not get it on your skin. Children should only complete this project in the presence of an adult.

Step 1: Gather and Mix the Ingredients

In the pot, mix:
· 4 beef cubes
· 1.5 envelopes of plain gelatin
· 1 cup of cold water
· 2 teaspoons of sugar

Step 2: Boil & Stir

After placing all the ingredients in the water, allow it to boil while constantly stirring the mixture.

Step 3: Cooling

Once the mixture is free of clumps, take the pot off of the stove and allow it to cool.

Step 4: Transfer to Foil Muffin Cups

After the mixture has cooled for about 5-10 minutes, pour the mixture into the 6 foil muffin cups.  Fill each of the cups about halfway full.

Step 5: Allow the Gelatin to Solidify

Once each cup has been filled, allow the mixture to harden. This process can be expedited by placing the cups in the refrigerator. Solidification should take around 20 minutes.

Step 6: Storing the Gelatin Plates

After the mixture has solidified, place each cup in an air tight sandwich bag. This prevents any external contaminants from coming into contact with the surface of the gelatin. If you plan on inoculating the plates, do so within a few days in order to obtain the best results.

Step 7: Troubleshooting

After completing the previous steps, the gelatin should appear dark red.

The mixture should not move too easily when the foil muffin tin is jostled. If the mixture fails to solidify after refrigeration that means there was not enough gelatin in the mixture. Add 2 envelopes of gelatin if this is the case. If the mixture is sticky, too much gelatin was added. In this case, use 1 envelope of gelatin instead of 2.

If there is anything unclear in these instructions please let me know, feedback is welcomed.