Tech Tuesday: Vegan Spider Silk

Image by GollyGforce – Living My Worst Nightmare

So, couple of weeks back, I did a Tech Tuesday about recycling, and focused mostly on plastics. Particularly, the oh so handy, and oh so problematic single use plastics. One of the points I made was that plastics that truly biodegrade aren’t really the best plastics. They are very short-lived plastics, suitable for compost bags, take out containers, and grocery store produce bags (etc.). One of the implications of that was that someday we might come up with plastics that were as good as what is there today, while also being fully biodegradable.

Who knew that someday was two weeks away?

What this is, is essentially making plastics with plant-based proteins. In this case, Soy Isolate Proteins (SIP), which are a by-product of soy production. Proteins, because they are very twisty molecules, are very good at forming long chains. What they aren’t is very soluble. The way you get any molecules to form the long chains needed to make a polymer is to dissolve things, then as it dries out, the chains form. What this team did was use a mild acid (acetic acid, the acid part of vinegar) and an ultrasonic treatment to get the plant proteins to dissolve. Once dissolved, the solution is heat treated (to 90 degrees C) and the solvent is removed (I assume evaporated away, but maybe it’s just drained off), leaving a self-assembled protein polymer film behind.

A key takeaway here is that none of this is ‘tricky’. Pour the SIP into a vat of acetic acid, play it a song at ultrasonic frequencies until it all dissolves, warm it up to just about boiling, let it cool down and remove the acetic acid. That just screams ‘industrial scalable’.

So where does the ‘Vegan Spider Silk’ come into this? Spider silk (and silk fabric, for that matter), are nothing more than proteins dissolved in a solution in the insect’s body, and when that solution is expelled, it quickly dries and the proteins form long, very strong, molecular chains¹. So, this is making spider silk, but forming it into sheets and films, instead of threads. The Vegan part comes from the lack of animals or insects in the process. No need to kill silk moth pupae, or try to harvest silk from spiders².

And being that it is just chained together proteins, it’s as biodegradable as a spider web, or a cocoon, or a silk shirt.

I doubt we’ll be using this version of it for anything beyond short term food packaging (plastic windows in the deli sandwich box, or some analog of cling wrap), but that depends on how long it can hang around before it starts to degrade. I mean, spider egg sacks seem to stay stuck to the roof of my front porch for the better part of a year, and silk shirts aren’t falling apart in the closet just because they got washed. So, who knows, it might be more useful than just that.

Oh, for those interested, here is the Nature article.

1. Remember that spider silk is, kg for kg, stronger than steel
2. Spiders are already rather ornery creatures, and trying to make them make silk makes them even more ornery