Consider it as an addendum for PcMan answer, mostly on economic feasibility.
At uni, we did grow E. Coli and in the context of the question, it can be said we had a funny substrate for their happy growth. The substrate was meat soup(sort of, how it was made), we even joked about tasting it, but yeah didn't happen, the thing was like 20 y.o. stuff in the bottles, color like soy sauce. We diluted it, added salt, and used it to grow night cultures(concentrations of bacterias like 1e8/cm3, or something, forgot it), made agar with it for Petri dishes.
In that sense economical feasibility, if you rob an old soviet lab for this magical stuff it can be economically feasible, even if you are better off with just drinking it.
But otherwise, it depends on different factors.
The efficiency of a process, they do not eat all of it because of their own byproducts, other strains of different stuff start to catch up with those in a few days later and all that.
So for a full conversion of your substrate, you lose energy anyway in such conversion, but additionally, for that, you have other means on top to keep your tasty strain of bacterias to be a predominant inhabitant of a substrate, and you have to remove their byproducts (a result of metabolism) for them to enjoy it further.
Removing byproducts and keeping culture to stay monoculture is an effort in the first place, but how big these efforts are - it differs depending on what is grown and how it is grown.
In that sense bacterial mats(SCOBY) like the kombucha thing it super easy - one removes byproducts by drinking it and replenishes it with tea and sugar. Sometimes it can get infected, just peal layer off, cut off that piece and you are done. If one keeps cleanliness while operation on a level of "wash your hands", do not touch the thing - it enough to not have such problems at all.
Keeping E. coli to be a single strand is also relatively simple, just your regular lab procedures seed it to get a colony, grow that colony. Or like that E. coli long-term evolution experiment on their site they have their working procedure but basically, it is done by having backup copies in a freezer and detecting contamination.
- but with a petri dish, you know once you open it the next day, remove the lid, it will go bad in few days(3-4-5) due to mold or something strange. Even if you do not open it it will take longer but it will happen. To prevent reduce chances it needs a cleanroom environment, we had regular ones cuz operation procedures are less expensive and we didn't need those for what we did in the way we did. But that meat growth may require more strict conditions.
With yeast it is also easy to remove byproducts, also in line with a drink-it behavior, you know, and that higher C2H5OH is their protective mechanism to keep themselves the only consumers of the substrate. (if they are in the anaerobic mode, for mass aerobic mode is preferable, more mass of result product, but things may or may not become a bit harder)
All those more or less are liquid states, cultures have some tricks this or another way because they are alpha predators on that microbiological level, more or less.
But grow meat and recreate texture at the same time protecting it from spoiling, because any bacteria or mold wants to corrupt eat it as well, so as its substrate - it is a situation similar to sheep against wolves - that can be a challenge. Mammal bodies can do that because of the immune system and skin and few other tricks. Challenge looks like 10x compared to a regular lab situation and culture.
- and here I would like to be more specific, but I do not know what they do to grow meat things.
So your efforts go up as well, decreasing the economic feasibility.
energy, nutritional value
13.91 MJ/kg energy value for dry yeast, and conversion ratio plant matter and such to yeast is like around 28%, as I see from nonenglish sources, not super credible as well, for English references it may be useful to look up "Yeast cow feed" or something, it used as making supplementary feed for cows and such.
Dry meat nutrition value is about the same https://www.eatthismuch.com/food/nutrition/dry-meat,2118470/
So if you have similar water content as the nutritional situation it can be 1:1, which is somewhat expected.
So in a sense of energy, substrate conversion can be around 30%, and if we take sugar as a price gauge for a substrate which is 1/10 of meat price then as result it is possible to have endproduct of 0.3 prices of meat.
One needs macro and microelements to grow stuff, not a big deal, look aquaponics prices for that, not expensive stuff.
So the question of economic feasibility lays in - is it possible to squeeze the procedures in below that 0.7 leftover prices, for the strain of a culture you need for the purpose. And it heavily depends on that culture and procedures it requires. For some random cultures, it can be easy, with others it clearly can be expensive on a lab scale. As for industrial-scale, there is some potential, but it heavily depends on specifics.
It depends on what you are ready to eat, but yes it can be cheaper. Try worms btw, the red worms especially. Paper(cardboard) and leaves are what they need.
Yes, it is just a biological matter, it can have different digestive values due to different factors, but we are made of pretty much the same stuff energy-wise. Autolysis can be your friend in some cases, for yeast as an example.
It depends on what it is. (Here should be a screenshot from soy sauce factory, their fermenting barrels, and a guy tasting it happily(kinda, he is japan, he had strange tasting/thinking face), without any explanation to it, but ... - yeah definitely meme material from the future).