Pursuing the Perfect Performer of Fermented Beverages: GMMs vs. Microbial Consortium

Fermented beverages are widely diverse around the world and their quality is largely based on the organoleptic characteristics developed by the metabolism of the microorganisms present during fermentation. In order to achieve controllable processes in fermented beverages along with organoleptic complexity, two divergent approaches have been followed in terms of inoculum development: (1) the inoculation of multiple microorganisms, intending to promote synergism and favor organoleptic complexity derived from the metabolic diversity, and (2) the genetic modification of a single strain with the intention that it performs multiple functions. In this chapter, we discuss these divergent approaches, their achievements and perspectives

Growth Kinetics for the Selection of Yeast Strains for Fermented Beverages

Criteria to select autochthonous yeast strains for their use in fermented beverages include their ability to dominate the media and to enhance desired sensorial characteristics and their inability to produce undesired compounds such as biogenic amines or off-odors. One of the key features in yeast selection is its Implantation, surpassing different stresses, and its fermentation performance, which requires setting up the process and monitoring it, involving important amount of resources. Methods to evaluate the tolerance of yeast strains are usually based in the qualitative measure of the growth of the microorganism in a medium containing the limiting compound after a specific time of incubation. However, studying strain growth through optical density measurements permits to estimate quantitative and comparable parameters providing an insight into the fitness of the cell to certain environment, lag phase duration, growth rate, and maximum population, among others. In the last decades, culture-independent methods have been used to evaluate the dynamic of microbial populations during fermentative process. In this chapter, a review of recent advances in the selection of fermentative yeasts as well as the utilization of kinetic evaluation and molecular strategies in conditions associated with fermented beverage for selecting yeast strains is presented

Mechanisms of resistance in postharvest fruit-pathogen interaction

The objective of this review was to bring together concepts related to studies aimed at elucidating defense mechanisms against disease-causing agents, mainly in postharvest. Like plants, fruits are exposed to attack by pathogens that cause rot during postharvest storage, resulting in considerable losses. To control these pathogens, synthetic chemicals are used; however, since they are toxic, genetic resistance is regarded as a viable alternative. Fruits can withstand pathogens by means of physical barriers (presence of thick cuticular or trichome layers) and chemical ones, or through induced defenses that are activated once the host detects the presence of the pathogen, triggering the oxidative burst during the early hours of interaction. This burst entails the generation of reactive oxygen species (ROS), such as superoxide (O2ˉ), hydroxyl radical (OHˉ) or hydrogen peroxide (H2O2), and the activation of genes involved in several metabolic pathways. The study of such mechanisms may allow detecting disease-resistant genetic materials, thus reducing the use of toxic products.Este trabajo ha sido financiado por el gobierno español a través del proyecto AGL2011-30519-C03-03 y por el Consejo Nacional de Ciencia y Tecnología de México a través de los Fondos FOMIX-QRO-2010-C01-145514

Agricultura sostenible: detección de la podredumbre gris determinada por PCR en viñedos de Querétaro

El cultivo de la vid ha cobrado importancia en Querétaro, debido a que su producción repercute en la economía del estado; sin embargo, parte de esa producción se pierde debido a enfermedades, como la podredumbre gris, ocasionada por el hongo Botrytis cinerea. Para su pertinente control, es necesario optar por un método de detección, como las técnicas moleculares basadas en la reacción en cadena de la polimerasa (PCR). El objetivo fue estandarizar la PCR convencional para detectar B. cinerea en vid; para ello, se muestrearon uvas cv. "Merlot" en viñedos del estado: El Rosario (FRo), Bodegas de Cote (BCo) y Azteca (VAz). La PCR convencional se optimizó utilizando dos pares de oligonucleótidos específicos para B. cinerea (C729+/- y BC108/53) y se validó amplificando ADN de diferentes cepas de B. cinerea y otros microorganismos asociados a la vid. Finalmente, la técnica estandarizada se utilizó para determinar la incidencia de B. cinerea en los viñedos. Los iniciadores C729+/- presentaron un amplicón de 750 pb solo con el ADN de B. cinerea. Los viñedos mostraron baja incidencia de B. cinerea (15%); la más alta fue en VAz (p=0.017), seguido de BCo y FRo. Entre estos dos últimos no hubo diferencias significativas; se obtuvo 9.5 y 7.5%, respectivamente. La diferencia obtenida en la incidencia podría atribuirse al manejo cultural del viñedo y al inoculo primario presente en campo, puesto que no se encontró relación con las condiciones climáticas