Lactic acid has a wide range of applications in food, pharmaceutical, chemical and cosmetic industries, among others. Recently, a great deal of interest has been devoted to the production of pure L(+) or D(-) lactic acid and their transformation into biodegradable lactide polymers (PLA). Research efforts have been focused on reducing production costs, throughout new substrates, new fermentation techniques, and emerging microorganisms capable of achieving high concentration, high productivity and high yields of lactic acid. This review summarizes the knowledge on biotechnological lactic acid production.