I wasn't happy with how the milk agar we made on 26 Feb 2022 separated. I looked for milk agar protocols online and found one that suggested using half the concentration of skim milk powder.
Making Skim Milk Agar Plates
a recipe from sciencing.com:
https://sciencing.com/make-skim-milk-agar-plates-8305900.html
- materials needed:
- (2) 500mL beakers
- (1) 500mL screw top culture media bottle
- Distilled or deionized water (dH2O)
- 2g agar powder
- 10g skim milk powder
- Fill each beaker with 100mL dH2O.
- In one beaker, dissolve 10g skim milk powder.
- In the other beaker, dissolve 2g agar powder.
- Combine and mix the contents of the two beakers into a culture media bottle.
- Cap the media bottle but be sure to keep the cap loose, meaning about 1 full turn away from fully screwed on tight. The cap should jiggle a little when touched.
- Autoclave at 121⁰C and 15psig for 15 minutes. I used 30 minutes, because Wendy had to autoclave some LB agar at the same time for 30 minutes. Wendy didn't think it would make much difference for me-- in her experience, nothing bad has happened when media is autoclaved 30 minutes instead of 15. She said that anything more than an hour would be excessive from an energy use and diminishing returns perspective-- we won't gain much more sterility from autoclaving more than an hour.
Unfortunately, distinct layers formed again. I suspect that milk curdles at autoclave temperatures.
[Insert photo of layered agar.]
Here's a different recipe— twice the concentration of the above. It's from Salih, Yehya. (2020). Re: In place of skim milk powder what can I use for preparing Skim Milk agar?. Retrieved from: https://www.researchgate.net/post/In-place-of-skim-milk-powder-what-can-I-use-for-preparing-Skim-Milk-agar/5e90d06f7582b62b6a491e8f/citation/download.
Dear Richard Herman
We can use skim milk, agar and distilled water with a ratio of 10 gm: 2 gm: 90 ml for them respectively.
Best regards..