Hi Dave,
We've discussed it on here before, but essentially, Bolt Threads has some very fundamental flaws to their approach.
First, there "technology" is not new. It has been used for decades to make proteins such as insulin. They genetically modify yeast to create a protein. This is a very expensive process and it yields very small amounts of protein compared to the quantity of your initial medium (mixture within your fermentation tank). You can do this with almost any protein that is small enough for the yeast to metabolize. There are tons of labs that you can contract out to produce your desired protein. You send them the protein you want, they send you the purified protein (for roughly the $37,000/kilo pricing that has been posted on Kraig Labs website). What Bolt essentially did is just choose a certain spider silk protein to be produced this way. This is also the same way that the other competitors make their silk protein. No part in this process has any significant breakthroughs in order to increase the amount of protein yield they receive from these yeast cells. If there were, it would be huge scientific news and spider silk would doubtfully be the first product produced from this new process (also, I read all their patent applications, they are using the exact same decades old process with no breakthroughs, not surprised).
Second, because the yeast is such a basic organism, it doesn't have the metabolic pathways to create large/long proteins the way complex organism like cows, humans, rats, spiders, or silkworms can. And spider silk is a very long repetitive protein chain. This is what gives it it's amazing properties. Each hydrogen bond on this long repetitive chain is attracted to the hydrogen bond of a nearby chain. So the longer the chain, the more bonds are interacting with each other, and ultimately, the stronger the fiber is. For bolt, the protein chain that the yeast can produce is a cut-off version of native spider silk protein. So technically, at the molecular level, Bolt has spider silk protein, which is why they can claim it. But, unfortunately for them, it is very short, so it doesn't have properties even close to native spider silk. So unless the scientific community all of a sudden discovers a yeast that can produce large proteins (more than 4-500 kDa) then Bolt is out of luck for ever getting a long enough protein that would even come close to spider silk properties (heres a hint: Scientist have been trying to find one for a long time and haven't)
Third, once Bolt has the protein (which takes a ton of purification to separate it from the rest of the medium because they have to make it into a powder first), they then have to make it into a thread which is an entirely other complex process that adds major costs. This would increase there costs from the published costs of protein production from companies that only produce the protein in liquid form. (sorry if that doesn't make sense.
There are other issues that I won't really get into, like how there process is in no way sustainable because the ammount of water and sugars needed to feed the yeast to make minute ammounts of protein, but I'll save that for another day.
For the sake of time, I didn't go into any scientific details so this is very broad strokes, but I hope the above explanation helps.
