Native lactic acid bacteria (LAB) are capable of growing during winemaking, thereby strongly affecting wine quality. The species of LAB present in musts, wines during malolactic fermentation (MLF), and barrels/filters were investigated in wineries from the emerging wine region of Queretaro, México using multiplex PCR and culture. The resistance to wine-like conditions (WLC): ethanol (10, 12, and 13%), SO2 (30 mg⋅l-1), and low pH (3.5) of native LAB strains was also studied. Five species were detected within 61 samples obtained: Oenococcus oeni, Lactobacillus plantarum, Pediococcus parvulus, Lactobacillus hilgardi, and Lactobacillus brevis. Four species (excepting L. brevis) were found in must; O. oeni and P. parvulus were ubiquitous in wine and L. plantarum and L. brevis were mainly present at the initial stage of MLF, while L. hilgardii was mostly detected at the advanced stage. Furthermore, some species detected in barrel/filter, prove them to be hazardous reservoirs. From 822 LAB isolates, only 119 resisted WLC with 10% ethanol; the number of strains able to grow in WLC with 13% ethanol decreased approximately by 50%, O. oeni being the most versatile species with 65% of resistant isolates, while Lactobacillus spp. and P. parvulus were the most strongly affected, especially those recovered from barrel/filter, with less than 10% of resistant isolates. This study evidences the presence of local strains able to be used as starter cultures, and also enabled the assessment of the risks derived from the presence of spoilage LAB strains resistant to WLC.

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Criteria to select autochthonous yeast strains for their use in fermented beverages include their ability to dominate the media and to enhance desired sensorial characteristics and their inability to produce undesired compounds such as biogenic amines or off-odors. One of the key features in yeast selection is its Implantation, surpassing different stresses, and its fermentation performance, which requires setting up the process and monitoring it, involving important amount of resources. Methods to evaluate the tolerance of yeast strains are usually based in the qualitative measure of the growth of the microorganism in a medium containing the limiting compound after a specific time of incubation. However, studying strain growth through optical density measurements permits to estimate quantitative and comparable parameters providing an insight into the fitness of the cell to certain environment, lag phase duration, growth rate, and maximum population, among others. In the last decades, cultureindependent methods have been used to evaluate the dynamic of microbial populations during fermentative process. In this chapter, a review of recent advances in the selection of fermentative yeasts as well as the utilization of kinetic evaluation and molecular strategies in conditions associated with fermented beverage for selecting yeast strains is presented.

A method to select yeast strains for fermentation taking into account the natural differences of yeast isolates. This methodology is based on the cell exposition to combinations of sugar and ethanol, which are the most important stress factors in fermentation. This strategy will help to identify the most tolerant strain that could improve ethanol yield and reduce fermentation time.

Fermented beverages are widely diverse around the world and their quality is largely based on the organoleptic characteristics developed by the metabolism of the microorganisms present during fermentation. In order to achieve controllable processes in fermented beverages along with organoleptic complexity, two divergent approaches have been followed in terms of inoculum development: (1) the inoculation of multiple microorganisms, intending to promote synergism and favor organoleptic complexity derived from the metabolic diversity, and (2) the genetic modification of a single strain with the intention that it performs multiple functions. In this chapter, we discuss these divergent approaches, their achievements and perspectives.

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The aim of this study was to isolate, identify and determine the oenological potential of yeasts present in Vitis vinifera organs of grapevines established in Queretaro State, Mexico. The yeast distribution was influenced by the organ and the sampling season, and the yeast populations ranged from 0.8 and 5.5 Log CFU/g. A total of 93 yeasts were isolated, identified by RFLP and confirmed by sequencing of the ITS region, prevailing Aureobasidium cf. melanogenum and Basidiomycota yeast. The identified species with previously reported oenological potential were: Pichia cf. kluyveri and Clavispora cf.opuntiae. Remarkably, P. cf. kluyveri 3.1HM showed killer phenotype and was the most tolerant to sulfur dioxide, and survived 72 h after its inoculation in ‘Tempranillo’ must. C. cf. opuntiae 5.7HM showed β-glucosidase activity, the highest tolerance to 5 % ethanol and 25 °Brix (sugar levels). On the contrary, Rhodotorula isolates were not tolerant to stress conditions, and R. mucilaginosa 8HM did not grow under must conditions. Mixed fermentation using H. uvarum NB108/S. cerevisiae N05 resulted in the highest volatile acidity (0.45 g/L acetic acid), while no differences for total acidity, alcohol strength, residual sugars and total SO2 were found between the mixed fermentations treatments. This study provides an insight into the yeast diversity present in grapevines established in Queretaro, Mexico, and the oenological potential of. P. cf. kluyveri 3.1HM.