Fermentation by lactic acid bacteria, molds and yeasts is one of the oldest methods for a safe preservation of foods. Many probiotics are a natural part of the beneficial gut microbiota and have a 'generally recognized as safe' (GRAS) status. Prebiotic carbohydrates such as inulin and fructooligosaccharides (FOS) are natural vegetable components and considered as GRAS. For prebiotics an eventual inconvenience is gas production in the gut. Possibilities to utilize probiotics to increase the safety in foods and drinking water.