VIEW ARTICLE    DOI: 10.1094/ASBCJ-63-0107

Analysis of Commercially Available Active Dry Yeast Used for Industrial Fuel Ethanol Production. E. Bellissimi and W. M. Ingledew (1), Department of Applied Microbiology and Food Science, College of Agriculture, University of Saskatchewan, Saskatoon, Saskatchewan Canada, S7N 5A8. (1) Corresponding author. Phone: 306.966.5028; Fax: 306.966.8898; E-mail: <ingledew@sask.usask.ca> J. Am. Soc. Brew. Chem. 63(3):107-112, 2005. Accepted December 20, 2004.

Seven industrial active dry yeasts (ADY) that are sold specifically for fuel alcohol production, but which may have brewing, winery, or bakery lineage (due to unavailability of specially selected strains for fuel alcohol use), were obtained from different suppliers. All were subjected to traditional screening methods to assess viability, contaminant levels, fermentation rates, generation times, optimal fermentation temperature, and fermentative performance in normal and very-high-gravity corn mashes. They were also compared by using two molecular techniques, karyotyping and mitochondrial DNA analysis. It was observed that of the seven samples, one had a significantly lower viability compared with the expected industrial norm of approximately 2.2 × 10(^10) cells/g. One sample had high levels of contaminants (0.1% anaerobic bacteria), suggesting that this ADY should not be used because of the risk of bacterial contamination and subsequent loss of ethanol yield during fermentation. More importantly, of the seven ADY, molecular examination revealed only four distinct karyotypic patterns. Mitochondrial DNA analysis confirmed the karyotypic results, but only three distinct patterns could be seen. These results demonstrated that of the seven ADY, only three unique yeast profiles were present. These results strongly suggest that many of the industrially available ADY are similar and indicate that yeasts may have been purchased by contract for resale or that some companies may have procured, grown, and sold the yeasts of their competitors. Keywords: Activity, Commercial ADY, Comparison, Fuel alcohol, Karyotyping, mtDNA analysis, Saccharomyces cerevisiae, Traditional analysis

Siete levaduras activas secas industriales (ADY) que se venden específicamente para la producción de alcohol combustible, pero que podrán tener linaje de cerveza, vino, o pan (debido a la indisponibilidad de cepas especialmente seleccionadas para uso de alcohol combustible), fueron obtenidas de diferentes proveedores. Todas fueron sujetadas a métodos de investigación tradicionales para determinar viabilidad, niveles de contaminante, velocidad de fermentación, tiempos de generación, temperatura óptima de fermentación, y funcionamiento fermentante en macerados de maíz normales y de muy alta gravedad. También se compararon usando dos técnicas moleculares, cariotipo y análisis ADN mitocondrial. Se observo que de las siete muestras, una tenía una viabilidad perceptiblemente más baja comparada a la norma industrial prevista de aproximadamente 2.2 × 10(^10) células/g. Una muestra tenía altos niveles de contaminantes (0.1% bacteria anaerobia), sugiriendo que esta ADY no se utilice debido al riesgo de contaminación bacteriana y pérdida subsecuente de producción de etanol durante fermentación. De más importancia, el examen molecular de las siete ADY reveló solamente cuatro patrones cariotipicos distintos. El análisis ADN mitocondrial confirmó los resultados cariotipicos, pero solamente se podían observar tres patrones distintos. Estos resultados demostraron que de las siete ADY, sólo tres perfiles únicos de levadura eran presentes. Estos resultados sugieren fuertemente que muchas ADY industriales disponibles son similares e indican que las levaduras se pudieron haber comprado bajo contrato para reventa o que algunas compañías pudieron haber procurado, haber crecido, y haber vendido las levaduras de sus competidores. Palabras claves: Actividad, ADY comercial, Alcohol combustible, Análisis mtDNA, Análisis tradicional, Cariotipo, Comparación, Saccharomyces cerevisiae