This is something special to know about sauerkraut. You don’t actually need a culture to make it. The cabbage combined with salt will make its own good bacteria. These bacteria dominate and crowd out the harmful ones and preserve the food in a safe way. You can make sauerkraut with just salt. You must add salt with this method to inhibit the growth of bad bacteria and to create an environment that is safe.
When you add salt, submerge the vegetables under the water, the good bacteria will dominate and keep out harmful pathogens. The salt pulls water out of the cabbage (through osmosis), and this creates the brine in which the cabbage can ferment and sour without rotting. The salt also has the effect of keeping the cabbage crunchy, by inhibiting organisms and enzymes that soften it. I do believe that using a starter culture has a lot more benefits, but this is a good method as well and the health benefits are many.
I don’t recommend culturing other vegetables without a culture. Cabbage has its own special properties that make it safe and easy to culture with just salt and water.