And Carrying on the Asimov Theme...

In Isaac Asimov's The Caves of Steel, most of the nutritional needs of the vast population of Earth is met with specially-engineered fungi and yeast. It's a not-uncommon trope elsewhere in SF, too - Vernor Vinge uses it in A Deepness in the Sky, for instance, when he mentions the "bactries" the starfarers use to concoct organic materials.

So, we took a step down that road today.