What are self healing injection ports, and do you need them?

When using grain jars, the time will come where you need to place your spores inside the jar for inoculation. This can be done with cultures grown on agar, or in the form of liquid syringes as a spore syringe or liquid culture. This presents an issue as the contents of the grain jar are ideally sterile after you have pressure cooked or autoclaved them, and once the lid has been removed to insert the agar or liquid the contents have been exposed to the outside air, creating the possibility of contamination.


One common method to reduce this risk is through the use of still air boxes or flow hoods to reduce the chance that bacteria or moulds will land in your jars. Another alternative is the use of Self Healing Injection Ports on your jar lids, which will allow you to insert a syringe without opening the lid, removing the need for a SAB. This method only applies to teks that make use of spore syringe, and cannot be used for agar work. Therefore if you plan to use a lot of spore syringe opposed to agar for your inoculation, it is worthwhile knowing how to make and use a self healing injection port lid, If you plan to use mainly agar cultures for your inoculation, it’s best to stick to the SAB. It is likely you will find yourself doing both from time to time as they both have very distinct advantages. Agar allows you to identify suitable areas of mycelium to use for inoculation that are free from contam, and spore syringes are much quicker to make and use, however have a higher chance of contamination.

Jars with Self healing injection ports for growing mushrooms
Source: One Earth Mushrooms (https://www.youtube.com/watch?v=lN8VQDs7BBI&t=48s)

How to make a Self Healing Injection Port Jar Lid.

Equipment

(Example of ready made injection ports)
  • Jar Lids
  • Micropore tape or .22 micron self adhesive filters
  • High temperature RTV silicone or ready made self healing injection ports
  • Drill and drill bit

Notes on equipment:

The silicone you use will need to be able to withstand High temperature otherwise it will be destroyed during the sterilisation process and likely fall into your jars, ruining the contents.

Ready made self healing injection ports can be purchased online from amazon, and work effectively too. 

Steps for making a Self Healing Injection Port for Growing Mushrooms:

  1. Drill 5 holes in your lid. One centre hole for gas exchange, and 4 towards the outer rim for your injection sites. If you are using the ready made SHIPS, simply use the appropriate drill bit size. If you are making your SHIP with high temp silicone, simply make the hole about 5mm diameter or larger, giving you plenty of room to inject.
  2. For the high temp silicone, apply to both sides of your lid to cover the outer four holes, spread to cover roughly a 2mm overlap from the hole circumference. For the ready made SHIP’s simply place into the holes you have made
  3. Cover the one centre hole with micropore tape

Allow your silicone to set as per the manufacturer instructions and use, and reuse!

Tips:

A silicone that is marked as RTV indicates that it will set at room temperature (RTV = Room Temperature Vulcanising). This is what you want. When you are searching for high temperature silicone you may come across some that actually set at high temperatures. You want your silicone to set at room temperature, but be able to withstand high temperatures. That is the difference.

Micropore tape can be used as your primary gas exchange filter. This option is cheap, and easy, the integrity of the tape’s ability can be compromised by over stretching and repeated use. An alternative that will provide consistency is the use of .22 micron self adhesive filters, such as these. These filters are small enough to block contaminants while still allowing for gas exchange, each one will provide the same level of protection, allowing for consistency in your work.

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