Agar Formulae for All Occasions

All of these formulae assume a total final volume of one liter. If the listed ingredients do not make up one liter of volume, and most do not, then it is assumed that a measure of water is added to make up the difference. The first two are basics that should be sufficient for nearly all purposes. It has been brought to my attention that those formulas calling for vegetable juice have a marked tendency to boil over. You may want to use a larger than usual container when preparing them. It should also be noted that most city water sources, and many wells, produce water that is in the pH 8 to pH 9 range, and this can present problems when trying to produce a pH balanced agar. Distilled water can be had in most grocery stores for 60 cents a gallon or so. I strongly encourage the use of this, as it assist in obtaining repeatable results.

MEA

• 20 grams of agar
• 20 grams of malt extract
• 2 grams of yeast

PDA

• 20 grams of agar
• the strained broth produced by boiling 300 grams of diced potatoes in one liter of water for one hour
• 10 grams of dextrose
• optional 2 grams of yeast

DFA This is a very nice agar for mushroom growers to use in the step right before innoculating a bulk substrate.

• 20 grams agar
• 20 grams crushed dogfood

Meat Broth Agar
Take 500 grams of beef heart or very lean beef and grind it as finely as possible. Add 1 liter of water and and allow it to sit overnight in the refrigerator. Filter through cheesecloth and then boil for ten minutes. Skim the fat off and filter through filter paper or a coffee filter.

• the above described broth
• 1 gram of peptone (optional)
• this may require a buffer to raise the PH
• 20 grams of agar

Milk Agar
This was apparently used at one time for testing milk samples. It doesn't actually contain milk. I haven't tried this one out, and I wonder if the mention of only 12 grams of agar is correct. If someone tries this let me know how it goes.

• 5 grams Peptone or Tryptone
• 3 grams Yeast
• 1 gram dextrose
• 12 grams of agar

Crossely's Milk Medium
I understand this to have at one time been a test medium for canned good contaminants.

• skim milk to a total of one liter
• 10 grams of peptone
• 15 grams of agar

Merrick's V8 Medium
This one strikes me as somewhat of an overkill. Should grow just about anything however. Lactose is often available from homebrew stores as milk sugar. Most yeast cannot digest this simple sugar, or so I've been led to believe. Incidently this is intended as a low PH medium for the cultivation of lactobacilli and related genera. Citric acid or lactic acid can be added to further lower the PH.

• 500 ml of V8 vegetable juice
• 10 grams of tryptone
• 5 grams of lactose
• 3 grams of meat extract
• 15 grams of agar

V-8 Oatmeal Agar

• 50 ml V-8 juice
• 25 grams cream of oats (or else just plain oatmeal, ground finely if possible)
• 15 grams of agar