The superstars here are the lactobacillus bacteria, and they are all around us. In vegetable fermentation, we simply create excellent living conditions for the good lacto bacteria, so that they multiply and concentrate, and naturally process the veg.
This lacto-fermentation happens when the lacto bacteria eat the sugars in the veggies, and produce lactic acid.
Lactic acid is a natural preservative. It pretty well prevents the growth of harmful bacteria, preserves or even increases vitamin and enzyme levels, and improves digestibility by starting to break things down so there’s less work for your gut. This is all well-observed, mainstream science.
To kick off the fermentation, submerging cut up vegetables in salty water is all it takes. The lacto bacteria are already living on the veggies. They like it best when there’s no oxygen around, and underwater takes care of that. The salt kills of other competing bacteria, until the lacto army is built up to sufficient numbers to take over.
You’re nudging natural processes that are already going on in a particular direction, giving the lacto bacteria an extra advantage to their stuff. Simple!
(By the way, this is exactly the same basic process at work when you Bake sourdough bread.)
Next up, the few things you’ll need.