TY - JOUR
T1 - Rational Selection of Mixed Yeasts Starters for Agave Must Fermentation
AU - Larralde-Corona, Claudia Patricia
AU - De la Torre-González, Francisco Javier
AU - Vázquez-Landaverde, Pedro Alberto
AU - Hahn, Dittmar
AU - Narváez-Zapata, José Alberto
N1 - Publisher Copyright:
© Copyright © 2021 Larralde-Corona, De la Torre-González, Vázquez-Landaverde, Hahn and Narváez-Zapata.
PY - 2021/9/8
Y1 - 2021/9/8
N2 - Tequila and mezcal are both traditional Mexican liquors that are produced from cooked Agave spp. must fermentation and usually rely on spontaneous or pure Saccharomyces cerevisiae strain inoculation. In order to contribute to the rational selection of yeast starters for tequila and mezcal productions, we tested a collection of 25 yeasts originally isolated from mezcal musts, spanning 10 different yeast species. These strains were first characterized in a semi synthetic medium (labeled as M2, having 90 g/L fructose and 10 g/L glucose of initial hexoses) at 48 h of culture, observing a differential pattern in the consumption of sugars and productivity. Selected Saccharomyces strains left around 10 g/L of fructose and showed higher fermentation performance. However, some non-Saccharomyces strains, specifically from Torulospora (Td), Kluyveromyces (Km), and Zygosaccharomyces (Zb) genera, consumed almost all the sugar (i.e., Km1Y9 with <5 g/L) and had a high productivity of ethanol. In general, all Saccharomyces strains presented a high production of ethyl-butyrate, ethyl-decanoate, and ethyl-hexanoate with peaks of 10, 38, and 3 μg/L, respectively. In addition, some Kluyveromyces and Torulospora strains showed a high production of phenyl ethyl acetate (i.e., Km1D5 with up to 1400 μg/L); isoamyl acetate (i.e., Km1D5 and Td1AN2 with more than 300 μg/L), and hexyl acetate (i.e., Td1AN2 with 0.3 μg/L). Representative strains of the most productive genera (Saccharomyces, Torulospora, and Kluyveromyces) were selected to evaluate their fermentative performance and survival in a mixed culture on a medium based on Agave tequilana must, and their population kinetics was characterized using specific fluorescent in situ hybridization (FISH) probes in a qualitative and semi-quantitative analysis during fermentation. We observed that the mixture ratios of 0.1:1:1 or 1:1:1 (Saccharomyces:Kluyveromyces:Torulospora), maintained good fermentation productivities, with alcohol yields above 0.45 g/g, and allowed a high survival rate of the non-Saccharomyces strains during the fermentation process. Finally, mixed inoculum fermentations on A. tequilana must medium, including different Saccharomyces strains and the finally selected Torulospora and Kluyveromyces strains, showed the best production parameters in terms of ethanol, carbon dioxide, glycerol, and acetic acid values, as well as improved volatile metabolite profiles as compared to the pure cultures. All these data were used to propose a methodology of selection of strains to be used as a pure or mixed starter for tequila and mezcal fermentations, with high primary metabolite productivity and desired aromatic profile.
AB - Tequila and mezcal are both traditional Mexican liquors that are produced from cooked Agave spp. must fermentation and usually rely on spontaneous or pure Saccharomyces cerevisiae strain inoculation. In order to contribute to the rational selection of yeast starters for tequila and mezcal productions, we tested a collection of 25 yeasts originally isolated from mezcal musts, spanning 10 different yeast species. These strains were first characterized in a semi synthetic medium (labeled as M2, having 90 g/L fructose and 10 g/L glucose of initial hexoses) at 48 h of culture, observing a differential pattern in the consumption of sugars and productivity. Selected Saccharomyces strains left around 10 g/L of fructose and showed higher fermentation performance. However, some non-Saccharomyces strains, specifically from Torulospora (Td), Kluyveromyces (Km), and Zygosaccharomyces (Zb) genera, consumed almost all the sugar (i.e., Km1Y9 with <5 g/L) and had a high productivity of ethanol. In general, all Saccharomyces strains presented a high production of ethyl-butyrate, ethyl-decanoate, and ethyl-hexanoate with peaks of 10, 38, and 3 μg/L, respectively. In addition, some Kluyveromyces and Torulospora strains showed a high production of phenyl ethyl acetate (i.e., Km1D5 with up to 1400 μg/L); isoamyl acetate (i.e., Km1D5 and Td1AN2 with more than 300 μg/L), and hexyl acetate (i.e., Td1AN2 with 0.3 μg/L). Representative strains of the most productive genera (Saccharomyces, Torulospora, and Kluyveromyces) were selected to evaluate their fermentative performance and survival in a mixed culture on a medium based on Agave tequilana must, and their population kinetics was characterized using specific fluorescent in situ hybridization (FISH) probes in a qualitative and semi-quantitative analysis during fermentation. We observed that the mixture ratios of 0.1:1:1 or 1:1:1 (Saccharomyces:Kluyveromyces:Torulospora), maintained good fermentation productivities, with alcohol yields above 0.45 g/g, and allowed a high survival rate of the non-Saccharomyces strains during the fermentation process. Finally, mixed inoculum fermentations on A. tequilana must medium, including different Saccharomyces strains and the finally selected Torulospora and Kluyveromyces strains, showed the best production parameters in terms of ethanol, carbon dioxide, glycerol, and acetic acid values, as well as improved volatile metabolite profiles as compared to the pure cultures. All these data were used to propose a methodology of selection of strains to be used as a pure or mixed starter for tequila and mezcal fermentations, with high primary metabolite productivity and desired aromatic profile.
KW - Agave
KW - Kluyveromyces
KW - Saccharomyces
KW - Torulaspora
KW - aroma profile
KW - mezcal
KW - mixed starter
KW - tequila
UR - http://www.scopus.com/inward/record.url?scp=85115387685&partnerID=8YFLogxK
U2 - 10.3389/fsufs.2021.684228
DO - 10.3389/fsufs.2021.684228
M3 - Artículo
AN - SCOPUS:85115387685
SN - 2571-581X
VL - 5
JO - Frontiers in Sustainable Food Systems
JF - Frontiers in Sustainable Food Systems
M1 - 684228
ER -