They're baking up soy hemoglobin in yeast and purifying it to add to non-meat burgers. This is particularly neat considering how complex the human heme synthetic pathway is. I suspect even in soy, it's more than just producing a "pre-(a-)"protein-- you'd have to make a few other enzymes along the heme synthetic pathway and provide an environment conducive to them working.
It does make me wonder, why soy? Corn and rice hemoglobins, unlike soy hemoglobin, are basically ubiquitous in our diet as far as I know. I suppose soy hemoglobin may be more meat-like or easier to produce.
I’m not an expert, but I know that soy is used as a nitrogen replacing plant during crop rotation. So it’s possible that the cost of soy is lower than rice or corn, as it’s an off cycle replenishing plant.
Jan 2018 cost per ton:
Soy: 405
Corn: 155
Rice: 442
Well! There goes that idea! Is the US corn subsidy the reason it’s so much cheaper?
Maybe a part of the price difference can be explained by the fact that corn (maize) uses the C4 photosynthesis vs the less efficient C3 used by soy and rice.
This paper (Figure 2) lists the protein sequences of 14 different plant hemoglobins. I am no expert, but they don't seem too different to me, any of them.
It does make me wonder, why soy? Corn and rice hemoglobins, unlike soy hemoglobin, are basically ubiquitous in our diet as far as I know. I suppose soy hemoglobin may be more meat-like or easier to produce.