Physiological characterization of two native yeasts in pure and mixed culture using fermentations of agave juice

Abstract

2019. Physiological characterization of two native yeasts in pure and mixed culture using fermentations of agave juice. Cien. Inv. Agr. 46(1): 1-11. Yeast cells are subjected to diverse environmental conditions during the alcoholic fermentation of agave juice, causing different kinetic behaviors. Agave juice was used as culture medium to evaluate the kinetic behavior of Saccharomyces cerevisiae ITD-00185 and Torulaspora delbrueckii ITD-00014a, as pure and mixed cultures, under different inoculum sizes (1×10 5 , 1×10 6 , 1×10 7 and 1×10 8 cells mL -1 ), and combined pH levels (3.5, 4.0 and 4.5) and temperatures (18 °C, 28 °C and 38 °C). Saccharomyces cerevisiae displayed high fermentation capacities at all inoculum concentrations assayed. However, T. delbrueckii required a high inoculum concentration (≥1×10 7 cells mL -1 ) to perform at fermentation levels similar to S. cerevisiae. Low temperatures (18 °C) slowed fermentation, while high temperatures (38 °C) adversely affected the development of the yeast strains, especially T. delbrueckii. The best temperature was 28 °C in all fermentations. The pH level had a strong effect on the performance of the coculture, since the fermentation kinetics suggested a synergistic effect at pH 4.5, while an antagonistic effect was postulated at pH 3.5. In all of the mixed culture cases, a positive effect at 28 °C, especially at pH 4.0 and 4.5, was demonstrated by greater levels of sugar consumption and ethanol production (~20%, p<0.05) compared to fermentations of the S. cerevisiae monoculture. The coculture results allow us to postulate that a complex interaction exists between the two yeasts, which could be synergistic or antagonistic, as the environmental conditions change.

Traditional Fermented Beverages of Mexico: A Biocultural Unseen Foodscape

“…Similar examples exist around the world and, recently, the use and characterization of starter cultures has been a main trend of research that could be used to improve fermentations and prevent the possible risk of spoilage [157][158][159]. This is, for instance, the case of traditional and industrial production of wines [160][161][162][163][164]. However, there are still few studies identifying and characterizing traditional starter cultures for traditional products in Mexico.…”

“…The practice of selecting fermentative environments or controlled facilities is common; for instance, people procure fermenting inside the house or special areas to control the external environmental heterogeneity in light incidence, temperature, external contaminants, or pathogens. Moreover, there is a cultural selection of the person who performs the fermentation and the substrate's quality [22,23,97,163,164]. A commonly overlooked aspect is how the microbial communities of starters are selected, prepared, conceived, stored, and used by local fermenters looking for the most favorable composition to improve the quality of their final products.…”

“…The interrelationships between the native microbial strains, substrates, techniques, tools, and fermentative environments of TMFB have been little studied. We identified studies that characterized the clay pots or tinas de fermentación for pulque [164] and tesgüino [85]. In fact, for tesgüino clay pots, fermenters use the specific name of tesgüineras and if the clay pot is broken, the pieces are trembled inside a new one, thus maintaining the microbiota from the old one.…”