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Old June 13, 2013   #42
greentiger87
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Join Date: Aug 2012
Location: Houston, TX - 9a
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So.. I've been culturing a certain biological antifungal product that many of us have found extremely useful. And it's been really successful! It's a streptomycete. I'm using a submerged culture technique, inoculating directly from the product with each batch, and using the product immediately. So basically, this allows the product to go a lot further - but you still need to buy it.

I've cultured 5 times now successfully, with a few failures. I'm using a 5 gallon bucket filled to about 3.5 gallons and an aquarium air pump with two airstones (each a cube of 1 inch).

Success is incredibly obvious because of the sweet smell streptomycetes produce. The effects on plants are pretty unmistakable as well.

I've tried a few different "recipes". The important thing is to keep nitrogen relatively low, use no simple sugars, and as few simple carbohydrates as possible. This favors actinobacteria over other bacteria. The most successful recipe is below.

1/4 cup crab or shrimp shell (provides chitin along with other macro and micro nutrients)
1 tbsp vinegar (this brings my tap water to slightly below neutral pH)
2 quarts of tapwater (my tapwater is hard, high in sodium, and alkaline)
1/4 cup cornmeal (carbohydrate and other nutrients)
1 tsp brewers yeast powder (provides full spectrum of nutrients and possible minor growth factors)

Chitin as the primary nitrogen source promotes the production of antifungal enzymes/metabolites and favors actinobacteria. For actinobacteria, the brewers yeast powder may actually be counterproductive. Actinobacteria are well adapted to situations with very little nutrition, and perhaps no exogenous growth factors, unlike many bacteria. However, it is a standard component of many culture mediums. I haven't yet experimented with leaving it out, but I will.

Do not add molasses, honey, sugar, or anything remotely sweet. It's just not necessary for actinobacteria, and will likely result in other bacteria taking over the culture. I've tried. The smell was horrible.

Cornmeal is very, very cheap at feed stores.

I powder the ingredients in a spice grinder if necessary.

Option 1) Tyndallization - Mix the solids and liquids in a stockpot. Bring to a low boil for thirty minutes, replacing water as needed. Let it sit overnight, covered. Boil again for thirty minutes and it's ready to use.

Pressure cookers used to scare me, so this is what I would have done in the past and have tried twice with success on this organism. Allowing the liquid to sit overnight promotes the germination of dormant spores that weren't killed by the first boiling. The second boiling kills most organisms before they have a chance to sporulate again.

Option 2) Ghetto Autoclave - Stick everything in a pressure cooker and let it go to three whistles or whatever makes you happy. Add extra water to account for the lost steam. Can be ready to use within 30 minutes of mixing.

Now you just dump everything in a well cleaned 5 gallon bucket and dilute to about 3.5 gallons. Turn on the pump, and add a tsp of the product. Wait three days or so. Smell it when you get impatient to reassure yourself.

Airline tubing, bubble stones, and the 5 gallon bucket should be thoroughly cleaned and disinfected after every use. Note that the air you're blowing into the culture is obviously not disinfected or sterilized. Apparently the streptomycete has enough of a headstart that this is not a problem.

I haven't had to use any chemical fungicides so far this season!

Last edited by greentiger87; June 13, 2013 at 11:11 AM.
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