title: Improvement of growth, fermentative efficiency and ethanol tolerance of Kloeckera africana during the fermentation of Agave tequilana juice by addition of yeast extract.
abstract: BACKGROUND
  The aim of this work was to improve the productivity and yield of tequila fermentation and to propose the use of a recently isolated non-Saccharomyces yeast in order to obtain a greater diversity of flavour and aroma of the beverage. For that, the effects of the addition of different nitrogen (N) sources to Agave tequilana juice on the growth, fermentative capacity and ethanol tolerance of Kloeckera africana and Saccharomyces cerevisiae were studied and compared.
  
  
  RESULTS
  Kloeckera africana K1 and S. cerevisiae S1 were cultured in A. tequilana juice supplemented with ammonium sulfate, diammonium phosphate or yeast extract. Kloeckera africana did not assimilate inorganic N sources, while S. cerevisiae utilised any N source. Yeast extract stimulated the growth, fermentative capacity and alcohol tolerance of K. africana, giving kinetic parameter values similar to those calculated for S. cerevisiae.
  
  
  CONCLUSIONS
  This study revealed the importance of supplementing A. tequilana juice with a convenient N source to achieve fast and complete conversion of sugars in ethanol, particularly in the case of K. africana. This yeast exhibited similar growth and fermentative capacity to S. cerevisiae. The utilisation of K. africana in the tequila industry is promising because of its variety of synthesised aromatic compounds, which would enrich the attributes of this beverage.
authors.affiliation: CIATEJ-Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco, Av. Normalista 800, 44270 Guadalajara Jalisco, Mexico. dmdm@ciatej.net.mx
authors.forename: Dulce M
authors.initials: DM
authors.lastname: Díaz-Montaño
authors.forename: Ernesto
authors.initials: E
authors.lastname: Favela-Torres
authors.forename: Jesus
authors.initials: J
authors.lastname: Córdova
mesh_terms: D027882:Agave / Q000382:microbiology*; D000434:Alcoholic Beverages; D000645:Ammonium Sulfate; D018929:Cell Culture Techniques; D000431:Ethanol; D005285:Fermentation; D005516:Food Microbiology; D005524:Food Technology; D055322:Kloeckera / Q000254:growth & development / Q000378:metabolism*; D009584:Nitrogen; D010710:Phosphates; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D015003:Yeasts
chemical_list: D010710:Phosphates; C024788:ammonium phosphate; D000431:Ethanol; D009584:Nitrogen; D000645:Ammonium Sulfate