Effect of Age of Agave tequilana Weber Blue Variety on Quality and Authenticity Parameters for the Tequila 100% Agave Silver Class: Evaluation at the Industrial Scale Level

Due to the oversupply and scarcity cycles of the Agave tequilana Weber blue variety, the effect of agave age (harvested in 4, 5, and 6 years) as raw material for the tequila 100% agave silver class was studied for each stage in a full-scale (industrial) process. Harvested plants showed differences in their morphological characteristics that affected the amount of juice; this had an impact in the fermentation stage since must composition was modified in the nitrogen content and juice/exudate ratio. This was noticed due to an increase in the production of higher alcohols attributed to the odd-chain fatty of the exudate, which affects n-propanol production. The characterization of the final product showed the feasibility to use agaves (less than 7 years) to produce the Tequila 100% agave silver class and to comply with the quality criteria. Furthermore, the final product was analyzed with the gas chromatography-isotope ratio mass-spectrometry technique to determine its authenticity. The δ13CVPDB isotopic parameter (−13.40‰ in average) values show the type of plant used as a raw material for ethanol production, while the δ18OVSMOW (20.52‰ in average) isotopic parameter can be helpful in corroborating and ensuring the traceability of the product and the geographical location of the beverage production.

Caracterización in silico y análisis de la expresión expresión génica de proteínas abundantes en la embriogénesis tardía de Agave tequilana Weber var. azul

Conocimiento previo/especie: Agave tequilana Weber var. azul es un importante cultivo en México, utilizado para la producción de tequila. Muchas especies de Agave son tolerantes a condiciones áridas. Sin embargo, las bases moleculares de los mecanismos seleccionados en los agaves para confrontar el estrés abiótico, no han sido descritas. Hipótesis: Las proteínas abundantes en la embriogénesis tardía (LEAPs), una superfamilia asociada a las respuestas ante el estrés abiótico en plantas, son un elemento clave en las respuestas de los agaves ante ambientes áridos. Métodos: Datos transcriptómicos de A. tequilana fueron utilizados para realizar análisis in silico e identificar genes que codifican Agave LEAPs. Comparamos sus características estructurales y su similitud/divergencia con LEAPs de otras plantas, utilizando bioinformática. La abundancia de los transcritos de AteqLEAP en órganos vegetativos y en respuesta a altas temperaturas fue determinada mediante qRT-PCR. Resultados: Identificamos tres AteqLEAPs estructuralmente diferentes. Las AteqLEA_5Bs muestran similitud (relativamente baja) con LEAPs conocidas como “atípicas” (LEA_3) y exhiben, inesperadamente, altos niveles de expresión constitutiva en hojas. Los transcritos de AteqLEA_5C (LEA_2) mostraron baja expresión en todos los órganos analizados. Dos isoformas de AteqDHN tipo SK3 muestran el típico desorden estructural e hidrofilicidad de las dehidrinas y son altamente expresadas en hojas no desarrolladas, meristemo vegetativo y tallo (piña). Conclusiones: Las AteqLEAP_5B parecen tener un papel protector preventivo en las hojas fotosintéticas plenamente funcionales; mientras que las AteqDHNs parecen proteger tejidos en proceso de diferenciación como meristemos y hojas en desarrollo; así como tejidos de almacenamiento, como el tallo del agave.

Role of xylose from acidic hydrolysates of agave bagasse during biohydrogen production

This study compares the H2 production from glucose, xylose, and acidic hydrolysates of Agave tequilana bagasse as substrates. The fermentation was performed in a granular sludge reactor operated in two phases: (1) model substrates (glucose and xylose) and (2) acidic hydrolysates at 35 °C, pH 4.5 and a hydraulic retention time of 5.5 with glucose (10 g L−1) and xylose (12 g L−1). A sequencing batch reactor was used to acclimate the biomass between the glucose and xylose continuous fermentation (with a mixture of xylose-glucose) and acidic hydrolysates. During the discontinuous acclimating step, the xylose/glucose ratio increment negatively affected the H2 productivity. Although the continuous H2 production with xylose was negligible, the co-fermentation with glucose (88–12%) allowed H2 productivity of 2,889 ± 502 mL H2 L−1d−1. An acidic hydrolysate concentration of 3.3 gcarbohydrate L−1 showed a 3-fold higher H2 productivity than with a concentration of 10 g L−1. The results indicated that xylose, as the only substrate, was challenging to metabolize by the inoculum, and its mixture with glucose improved the H2 productivity. Therefore, the low H2 productivity with hydrolysates could be related to the presence of xylose.