[hirundo]

We hear that eating vegetables is more efficient in ecological footprint than eating meat, since it cuts out the middle man. Is it yet more efficient to cut out the plants and get dietary protein from the bacteria that feed them?

[philipkglass]

Possibly, yes. This is the dream of so called "single cell protein" production. One type of SCP has been sold for years under the brand name Quorn (derived from a fungus rather than bacteria).

Bacterial protein may trigger allergic reactions in people and bacterial biomass is purine-rich which can also be a problem for people prone to gout. It's possible that cell engineering, directed evolutionary selection, or additional post-growth processing can minimize these problems.

I personally think that the more likely path is using fast-growing bacteria as feed for animal agriculture or aquaculture. Solar panels are so efficient at sunlight conversion compared to plants that you could farm salmon protein starting from bacterial pellets grown on solar derived hydrogen with per-hectare productivity comparable to conventionally farming soy beans. But the solar farm can go on saline, dry, contaminated, or otherwise agriculturally useless land. And salmon has slightly greater nutritional value than soy protein plus significantly greater market value.

[harimau777]

I know that Quorn also has a reputation for causing allergic reactions. However, I don't know if that reputation is deserved or just misinformation.

[cratermoon]

Plants use water, sunlight, and organic chemicals. In plants, protein is made from soil nitrates. Bacteria don't feed the plants, but they can fix nitrogen from the air into the soil. If we really wanted to cut out the middleman, we'd turn the nitrogen we breathe directly into proteins. For now, we have to eat to obtain the essential amino acidd, Histidine; Isoleucine; Leucine; Lysine; Methionine; Phenylalanine; Threonine; Tryptophan; and Valine