[MilaM]

Yes! Fermentation of fresh foods with lactic acid bacteria increases the acidity of foods and hence the shelf life. As far as I know, though, you also have to add salt to suppress the growth of less desirable microorganisms.

Edit: You can skip the fermanation step by pickling your vegetables with a suitable vinegar. The taste will be much different though.

[frogulis]

Yup, my understanding is that salt suppresses many bacteria, then the acid produced by lactobacteria (hopefully) suppresses botulism. Essential to ensure you have enough sugars to convert to acid! Test the pH in your ferments if you're giving them to friends!