DIY Selective Media

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aqualung42
Posts: 35
Joined: Mon Dec 02, 2019 12:32 am

DIY Selective Media

Post by aqualung42 » Tue Dec 10, 2019 1:33 am

PurposeTo eliminate or reduce contamination of unwanted fungi and bacteria on agar due to less the sterile conditions.

Background: As an amateur grower, growing fungi for culinary use, I am frequently encountering contamination issues, most often from a rust colored contaminant, but others as well in spite of using a still air box. Given my current amateur status, it seems like a waste of resources to invest in a flow hood. Selective media with readily available supplies, if possible, would solve this issue until investments in more advanced equipment is made.

Proof of Concept:
Day Zero
  • Four glad mini rounds were filled with agar and sterilized, 2 with an antibacterial agar(1), 2 with an anti-fungal agar(2).
  • One of each were inoculated with spores and one of each with mycelium.
    Containers were placed in incubator @ 85 degrees.
Day Seven
  • Both anti fungal media show no signs of growth or contamination.
  • Both anti bacterial media show signs of desired fungal growth, but also have rust colored contaminant.
Preliminary Conclusion:
  • Anti bacterial recipe seems to work. Fine tuning with a more controllable recipe should be explored.
  • Anti fungal recipe seems to kill desired mycelium and prevent desired spores from maturing. Perhaps less anti-fungal, or an anti fungal that uses a different mechanism might be able to select for desired fungi and against fungal contaminants.
Media Recipes:
  1. Anti Bacterial
    1. 1.25 mL CVS triple ointment (400 units Bacitracin Zinc, 5000 Polymyxin, & 3.5 mg neomycin per 14g tube.
    2. 1/4 cup Potato flake agar
    3. Ointment was added to hot agar and mixed thoroughly, then divided between two mini round containers.
  2. Anti fungal
    1. 1 mL 2% miconazole nitrate liquid
    2. 1/4 cup potato flake agar
    3. Made similarly to antibacterial media.

aqualung42
Posts: 35
Joined: Mon Dec 02, 2019 12:32 am

Re: DIY Selective Media

Post by aqualung42 » Mon Feb 03, 2020 9:29 pm

Whoa! I had a gormet culture I had thought was hopelessly contaminated, and as a last ditch effort to save it I tried some of the last of the syringe in some of my makeshift selective media and after a month and a half of neglect, give or take, I saw some familiar looking mycelium. They were only the size of a rice grain but given the odor I'd bet I salvaged them.

Gonna transfer small samples to a new formula selective media using powdered triple ointment instead of the petrolatum based. The latter leaves a greasy mess on the surface.

One small measuring scoop (weight to follow) of "Polvos de Sulpha 7.5 gm.69 oz. First Aid Antibiotic Powder" was added to 1/4 cup of hot nutrient agar. Medium was allowed to cure and sterilized under UV-C lamp for 30 min.

Will update with results

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