ABSTRACT
Since their discovery, and until recent times, microorganisms have generally been regarded as dangerous. In spite of the signifi cant work by Louis Pasteur on non-pathogenic microorganisms involved in lactic and alcoholic fermentations (1857), it was only after the second world war, that some microorganisms, especially bacteria, began to be considered useful for their probiotic properties. On the other hand, their use as starters for the beverage and dairy industry has been widely accepted, since, from the beginning of human history (4000-2000 BC) they were employed without awareness by Sumerians, Aegyptians and Babylonians to obtain wine, beer, vinegar and sour milk. Similarly, the industrial production of antibiotics, acetone, butanol and other useful products by means of microbial fermentation expanded before the second world war.
