Biotechnological potential of yeast isolates from cachaça: the Brazilian spirit.

This study identified phenotypic traits appropriate for biotechnological applications of 118 yeasts isolated from cachaça distilleries. Different properties were verified: capacity to use alternative carbon sources; ability to tolerate high concentrations of sucrose, ethanol, methanol, aluminum and zinc as well as different pH values and foam production. Pichia guilliermondii and Pichia anomala strains were identified as the most promising ones for application in the second-generation biofuel industry, showing ability to grow on high glycerol concentrations. Other isolates, identified as Saccharomyces cerevisiae, produced bioethanol comparable to the industrial strains, and were therefore ideal for use in the first-generation ethanol industry. Some of these strains also showed high resistance to aluminum, as observed in sugarcane juice, and to inter-cycle washings with diluted sulphuric acid, as performed in the industrial bioethanol production process. In summary, yeast isolates from cachaça distilleries displayed robustness and phenotypic plasticity, which makes them interesting for biotechnological applications.

Variable flocculation profiles of yeast strains isolated from cachaça distilleries.

In cachaça production, the use of yeast cells as starters with predictable flocculation behavior facilitates the cell recovery at the end of each fermentation cycle. Therefore, the aim of this work was to explain the behavior of cachaça yeast strains in fermentation vats containing sugarcane through the determination of biochemical and molecular parameters associated with flocculation phenotypes. By analyzing thirteen cachaça yeast strains isolated from different distilleries, our results demonstrated that neither classic biochemical measurements (e.g., percentage of flocculation, EDTA sensitivity, cell surface hydrophobicity, and sugar residues on the cell wall) nor modern molecular approaches, such as polymerase chain reaction (PCR) and real-time PCR (q-PCR), were sufficient to distinctly classify the cachaça yeast strains according to their flocculation behavior. It seems that flocculation is indeed a strain-specific phenomenon that is difficult to explain and/or categorize by the available methodologies.

Signals of aging associated with lower growth rates in Kluyveromyces lactis cultures under nitrogen limitation.

The effects of aging on the specific growth rate of Kluyveromyces lactis cultures, as a function of (NH4)2SO4 concentration, were evaluated. The growth kinetic parameters maximum specific growth rate and saturation constant for (NH4)2SO4 were calculated to be 0.44 h(-1) and 0.15 mmol·L(-1), respectively. Batch cultures were allowed to age for 16 days without influence of cell density or starvation. The specific growth rates of these cultures were determined each day and decreased as the population aged at different nitrogen concentrations. Aging signals (N-acetylglucosamine content of the cell wall, cell dimensions, and apoptosis markers) were measured. Apoptosis markers were detected after 5 days at limiting (NH4)2SO4 concentrations (0.57, 3.80, and 7.60 mmol·L(-1)) but only after 8 days at a nonlimiting (NH4)2SO4 concentration (38.0 mmol·L(-1)). Similarly, continuous cultures of K. lactis performed under nitrogen limitation and, at lower dilution rates, accumulated cells exhibiting aging signals. The results demonstrate that aging affects growth rate and raise the question of whether nitrogen limitation accelerates aging. Because aging is correlated with growth rate, and each dilution rate of the continuous cultures tends to select and accumulate cells with a respective age, cultures growing at lower growth rates can be useful to investigate yeast physiological responses, including aging.