I am in the process of working on a pressure cooker free method of making agar plates that do not contaminate even in open air conditions. I make my own e liquid for my vape so I always have propylene glycol on hand. Its antibacterial properties are often talked about in the vaping groups I am in so I looked into this further. A 1942 study found that vapor from a small amount of propylene glycol produced immediate and complete sterilization in the air. This was my starting point.

I have made up 9 test plates with only slightly altering my original agar recipe. Propylene glycol was added to the mix in a small amount. The nutrients were slightly decreased and the agar was increased to make up for the viscosity of the propylene glycol.

All 9 plates were simply cleaned with soap and water and then dried with no sterile procedures. I then mixed my agar media, poured, and the plates were left to completely cool in open air. The plates solidified with no issue. Three plates were coughed on by me, three plates were touched with my unsterile fingers, and the other three were left alone. They were then sealed with lids. These are dishes I have used for no pour, so no wrapping was done.

It has been 24 hours and as of now, all of the plates are 100% contamination free. I have seen bacterial contamination appear in as little as a few hours, so this is a great sign so far.

Propylene glycol is hygroscopic, so my thought process is that unsterile dishes can be poured with agar media and the media is sterile. Once sealed, the propylene glycol agar media creates a sterile environment within the dish due to its hygroscopic properties.

Propylene glycol is not toxic. The only issue I see going forward is that the hygroscopic properties may draw moisture from the mycelium. Though with the propylene glycol being mixed in with the agar media and being in a sealed dish, conditions of the media itself should be acceptable for mycelial growth.

I will be doing transfers to the propylene glycol dishes and updating with my growth results.