Sterilisation of Porous Scaffolds

I am looking for ways to pre-sterilising protocol my large scale scaffolds to grow
The scaffold is 3d printed with a material that has lignocellulosic particles and PVA (a water soluble polymer) here is the link :
Kai Parthy is an amazing engineer / designer /scientist / creator of these special filaments and the one I use is called “growlay”
The idea with this material is that you can use it with a regular desktop fused deposition printer, that extrudes thermoplastics. Great for people who want to avoid getting too deep into mechanics and hacking of the hardware.
After the print ends, you remove the PVA part by soaking it into water for two days (similar to rinsing away procedure of support structures of regular multi-material prints with PVA). After the object is dried out (NOT IN THE OVEN), what s left is the wooden particles that are glued by a backbone polymer. This means there is more surface area of lignocellulose on the scaffold where the fungi can grow on. IMG_20190813_130155|690x517](upload://ud7gEfQrI5PW3bJq3JTWoHx5oqF.jpeg)
But there are issues in my context especially with sterilisation:

  1. The structure is very porous both on micro and macro scale.
    So the sterilisation before introducing my intended mushrooms Reishi ( Ganoderma lucidum ) and Amadou *( Fomes fomentarius ), is very difficult.
    I have applied 1) Soaking in sterilised water, UV light exposure for days, 70%ethanol sprays, working in clean bench…
    BUt at the end just because I was scared, I overkilled with 10L of oyster spawn to avoid contamination. If I want to use liquid culture or less spawn, I need to sterilise better.
    @sebastionCocioba recommended I use NA-DCC as an easy way of bathing large objects for sterilisation.


The spawn needs to be applied after the scaffold is dried?
Because that drying period seems to be the main opportunity for contamination so if you can apply the spawn after removing the PVA, it should have an advantage over competing bacteria/fungi, no?

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I completely agree with you.
After the PVA is removed the the object becomes really wobbly and the mycelium application becomes really harder if I want to have some form retained.
What if I spray some liquid mycelium culture on the object after the PVA is removed? The liquid culture is not enough to compete with bad stuff ha?

No idea if the spray would be enough, maybe you have enough liquid spawn that you can do a second soak, after most of the pva is removed??

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Hmm, first I need to learn how to make a liquid spawn. I do not think that the mycelial cells that are attached on the structure after soaking will grow enough to fill the channels with solid matter though.
Maybe the liquid soaking method is good for making textile like objects or coating the print with mycelial skin…