The uses of AFLP for detecting DNA polymorphism, genotype identification and genetic diversity between yeasts isolated from Mexican agave-distilled beverages and from grape musts

Aims: The objectives were to determine the variability and to compare the genetic diversity obtained using amplified fragment length polymorphism (AFLP) markers in analyses of wine, tequila, mezcal, sotol and raicilla yeasts. Methods and Results: A molecular characterization of yeasts isolated from Mexican agave musts, has been performed by AFLP marker analysis, using reference wine strains from Italian and South African regions. Conclusions: A direct co-relation between genetic profile, origin and fermentation process of strains was found especially in strains isolated from agave must. In addition, unique molecular markers were obtained for all the strains using six combination primers, confirming the discriminatory power of AFLP markers. Significance and Impact of the Study: This is the first report of molecular characterization between yeasts isolated from different Mexican traditional agave-distilled beverages, which shows high genetic differences with respect to wine strains

Effects of the addition of different nitrogen sources in the tequila fermentation process at high sugar concentration

Aims: To study the effect of the addition of different nitrogen sources at high sugar concentration in the tequila fermentation process. Methods and Results: Fermentations were performed at high sugar concentration (170 g l -1) using Agave tequilana Weber blue variety with and without added nitrogen from different sources (ammonium sulfate; glutamic acid; a mixture of ammonium sulfate and amino acids) during the exponential phase of growth. All the additions increased the fermentation rate and alcohol efficiency. The level of synthesis of volatile compounds depended on the source added. The concentration of amyl alcohols and isobutanol were decreased while propanol and acetaldehyde concentration increased. Conclusions: The most efficient nitrogen sources for fermentation rate were ammonium sulfate and the mixture of ammonium sulfate and amino acids. The level of volatile compounds produced depended upon types of nitrogen. The synthesis of some volatile compounds increased while others decreased with nitrogen addition. Significance and Impact of the Study: The addition of nitrogen could be a strategy for improving the fermentation rate and efficiency in the tequila fermentation process at high sugar Agave tequilana concentration. Furthermore, the sensory quality of the final product may change because the synthesis of the volatile compounds is modified. Zapotitlán 2007 The Authors

Increasing fermentation efficiency at high sugar concentrations by supplementing an additional source of nitrogen during the exponential phase of the tequila fermentation process

In the tequila industry, fermentation is traditionally achieved at sugar concentrations ranging from 50 to 100 gm L-1. In this work, the behaviour of the Saccharomyces cerevisiae yeast (isolated from the juices of the Agave tequilana Weber blue variety) during the agave juice fermentation is compared at different sugar concentrations to determine if it is feasible for the industry to run fermentation at higher sugar concentrations. Fermentation efficiency is shown to be higher (above 90%) at a high concentration of initial sugar (170 g L-1) when an additional source of nitrogen (a mixture of amino acids and ammonium sulphate, different than a grape must nitrogen composition) is added during the exponential growth phase

Glucose and acetate influences on the behavior of the recombinant strainEscherichia coli HB 101 (GAPDH)

International audienc

In vitro interactions between ectomycorrhizal fungi and ericaceous plants

Sequential methodology based on the application of three types of experimental designs was used to optimize the astaxanthin production of the mutant strain 25-2 of Phaffia rhodozyma in shake flask cultures. The first design employed was a factorial design 25, where the factors studied were: pH, temperature, percent of inoculum, carbon and nitrogen concentrations, each one at two levels. This design was performed in two medium types: rich YM medium and minimal medium, based on date juice (Yucca medium). With this first design the most important factors were determined (carbon concentration and temperature) that were used in the second experimental strategy: the method of steepest ascent was applied in order to rapidly approach the optimum. Finally, a second-order response surface design was applied using temperature and carbon concentration as factors. The optimal conditions stimulating the highest astaxanthin production were: 19.7°C temperature; 11.25 g 1-1 carbon concentration; 6.0 pH; 5% inoculum and 0.5 g 1-1 nitrogen concentration. Under these conditions the astaxanthin production was 8100 ?g 1-1, 92% higher than the production under the initial conditions. " 2001 Elsevier Science B.V.",,,,,,"10.1016/S0168-1656(01)00279-6",,,"http://hdl.handle.net/20.500.12104/43399","http://www.scopus.com/inward/record.url?eid=2-s2.0-0035850234&partnerID=40&md5=9e24610d6355a27e6d8bba5f14bb281d",,,,,,"3",,"Journal of Biotechnology",,"25

Transitory plasmid instability during the exponential phase of growth of a recombinantEscherichia coli

International audienc

Optimization of astaxanthin production by Phaffia rhodozyma through factorial design and response surface methodology

Sequential methodology based on the application of three types of experimental designs was used to optimize the astaxanthin production of the mutant strain 25-2 of Phaffia rhodozyma in shake flask cultures. The first design employed was a factorial design 25, where the factors studied were: pH, temperature, percent of inoculum, carbon and nitrogen concentrations, each one at two levels. This design was performed in two medium types: rich YM medium and minimal medium, based on date juice (Yucca medium). With this first design the most important factors were determined (carbon concentration and temperature) that were used in the second experimental strategy: the method of steepest ascent was applied in order to rapidly approach the optimum. Finally, a second-order response surface design was applied using temperature and carbon concentration as factors. The optimal conditions stimulating the highest astaxanthin production were: 19.7°C temperature; 11.25 g 1-1 carbon concentration; 6.0 pH; 5% inoculum and 0.5 g 1-1 nitrogen concentration. Under these conditions the astaxanthin production was 8100 μg 1-1, 92% higher than the production under the initial conditions. © 2001 Elsevier Science B.V