Microbial Interactions in Fermented Beverages

FARÍAS M.E.; MENDOZA L.M.; AREDES FERNÁNDEZ P. A.; SOSA O. A.

Industrial Fermentation: Food Processes, Nutrient Sources and Production Strategies

Nova Science Publishers Inc

Lugar: Hauppauge NY; Año: 2009; p. 1 - 42

In complex microbial ecosystems constituted by a mixture of different species and strains, interactions will occur between individual microorganisms determining the final ecology. The general environment from which raw food products originate and the microbiological quality of the products in its processed state admits yeast growth. Only part of the primary microflora survives under the selective pressures exerted by the intrinsic and extrinsic biotic factors present in the ecosystem. Eventually, a particular yeast community will develop, and if environmental factors permit, a specific association would contribute positively or negatively to the final product. The types of interaction found in mixed populations of microorganisms are classified as direct or indirect interactions. Indirect interaction such as competition, commensalism, mutualism, amensalism or antagonism and neutralism; and direct interaction to predation and parasitism could be occurring. In fermented foods and beverages develop their nutritional and organoleptic qualities as a result of the metabolic activity of a succession of different microorganisms and it is unlikely that the interactions will separate into these discrete groups since more than one type of interaction occurs simultaneously. Considering wine production, the habitat presents an ecosystem where yeast-yeast, yeast filamentous fungi and yeast-bacteria interactions can be produced. The symbiosis of them depend on the yeast strain used providing amino acids, peptides and vitamins available as growth factors for lactic acid bacteria (LAB) development, or by the yeast ability to produce metabolic compounds which can act as inhibitors. Thus, interaction also can involve the antagonistic activity of yeasts against other microorganisms by means of the production or secretion of antibacterial a antifungal compounds, co-fermentation, and their role as in biological control. The flocculation is a phenomenon wherein the cells adhere in clumps and sediments rapidly from the medium in which they are suspended. This property could modify the metabolic behavior of the interacting cells. It is know that many microbes use extracellular signals to transmit information about population density and environmental conditions. As microbes continually need to respond to varying medium conditions, it is not surprising that quorum-sensing regulation that is modulated by physical factors and nutrients availability affect the interactions produced between microorganisms.