Can somebody explain how this is different to the "pleather" being made as a side-product from the production of Kombucha? Thats been a thing for a while now.
AFAIK its also grown by mould, from culture. But, it forms as a mat on top of the Kombucha fermenting liquid.
Here is what they say about pleather in their Sustainability section:
Mylo is also a more sustainable option than synthetic leathers, most of which are made from polyurethane or PVC, These so-called ‘pleathers’ are manufactured using numerous toxic chemicals. While not proven to be dangerous to humans during use, these toxic chemistries persist in the landfills and groundwater where they end up.
Reading elsewhere, it doesn't look like Kombucha is a pleather. If not, then they are different processes for creating different materials that are substitutes for leather.
(please help me where I'm wrong other scientists... But here's my basic knowledge.)
Leather as you know it are combinations a few different (known) structural proteins secreted from mammals between skin cells, after the skin cells themselves have been removed, and the proteins become chemically glued together (cross-linked). The majority of that protein is collagen.
Plether is a plastic fiber (petroleum derivative) that is spun and processed in such a way as to have an appearance similar to the final leather product (kind of, close enough). It's not protein-based in any way.
This new leather, 'Mylo', is a protein-based 'fabric' where the base protein is secreted by fungi rather than mammals. However, fungi are similar enough to mammals evolutionarily, that the proteins they secrete are evolutionary related to those secreted by our own cells to make our skin. The primary protein in both cases is collagen. Additionally, fungi genetics are easily manipulable, so you can actually insert the DNA that encodes for mammal-like collagen, other proteins found in animal leather, or proteins with new or completely different functions that would never show up on the skin of a mammal (color, water resistance, enzymatic capabilities, etc.).
tldr: Pleather is nothing like animal leather chemically - but has some similar bulk properties. This new MyLo is chemically related (evolutionarily) to animal leather, but ultimately comes from fungi. But because it's genetically known, it can actually include new capabilities that cannot be found in animal leather.
Yes, like us, fungi are opisthokonts, but where collagen is the mammalian structural protein used for making leather, fungal hyphae are principally comprised of chitin—structurally closer to the polysaccharide cellulose of the mentioned "kombucha leather" than to the collagen protein. Collagen is present in fungi in certain edge cases, but bulk mycelium is mostly chitin. This is speculation, but leather made from chitin may actually be a bit stronger than animal leather made from collagen. Maybe closer to keratin in strength? (Interestingly, keratin is chemically cleaved in hides during leather production--not entirely sure why, to enhance flexibility and allow access to the collagen fibers?). Agreed about fungi being easier to engineer. As you point out, endogenous expression of dyes in hyphae for different colors of mycelial leather is compelling. GFP would be cool too for the rave and nightclub crowd.
The Quorn meat analogue[1] is another product made from compressed mycelium. I've had "chicken" nuggets made from it. They're...not bad, but as far as mycelial structures go I prefer mushrooms.
I'm curious to know how well this new material handles exposure to humidity/water, as I've grown some of the kombucha leather and its durability seemed to go out the window once it becomes wet (and possibly is exposed to significant humidity).
AFAIK its also grown by mould, from culture. But, it forms as a mat on top of the Kombucha fermenting liquid.