For a mesophilic (Not sure about spelling) culture you can put one ounce in a quart of skim milk and make the culture. I use this for cottage cheese and sour cream.
Sterilize your jar.
Put in skim milk and boil for a half hour.
When the milk is at room temperature, you can add one ounce of culture.
Stir.
Let sit overnight and refrigerate.
It should look like yogurt and sometimes it has whey on top. This keeps in
the frig for about a week.
take my culture and freeze it in ice cube trays. One ounce equal one cube. I just keep a bag in my freezer and they are ready when I make cheese. Just remember to always keep one cube so you can make more culture. I do about 2 quarts at a time so I always have lots.
I know some people will tell you it looses it potency but I have no experienced that. Hubby's aunt does this and has been doing it for a long time with no problems.
I'm in a hurry so if the directions aren't clear, let me know.

Jess