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Fermentation kinetics of dairy-relevant sugars in acid whey conditions by Saccharomyces, Kluyveromyces, and Brettanomyces species.

V. K. Rivera Flores

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06-22-2020

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Abstract:

M52
Fermentation kinetics of dairy-relevant sugars in acid whey conditions by Saccharomyces, Kluyveromyces, and Brettanomyces species.
V. K. Rivera Flores*, T. A. DeMarsh, S. D. Alcaine. Cornell University Ithaca, NY.

Acid whey (AW) from Greek yogurt is an underutilized by-product and a challenge for the dairy industry. One valued-added scheme is the fermentation of AW -with or without the addition of lactase- by yeast such as Saccharomyces, Brettanomyces and Kluyveromyces spp. to produce new styles of fermented beverages. Previous research in our group observed changes in fermentation performance with lactase addition. Therefore, this work aims to describe the fermentation kinetics of dairy-relevant sugars by S. cerevisiae, K. marxianus and B. claussenii in simulated AW conditions to study alcoholic fermentation as an alternative for AW's reinsertion into the food supply chain. For this purpose, 4 preparations of yeast nitrogen base with amino acids with 40 g/L of lactose (LAC), glucose (GLU), galactose (GAL) or a 1:1 mixture of glucose and galactose (GLU+GAL), with a final pH of 4.20, were used as fermentation media. Each medium was inoculated with S. cerevisiae, K. marxianus or B. claussenii to achieve an initial concentration of 4 � 106 cfu/mL in 500 mL and incubated at 25�C under anaerobic conditions, while density, pH, cell count, ethanol and organic acids were monitored. Statistical analysis was done using Tukey's HSD test. Results indicated that K. marxianus had a similar or better performance compared with S. cerevisiae, whereas B. claussenii sugar consumption rate was substantially lower. In particular, densities showed that there is no significant difference in the time that K. marxianus and S. cerevisiae need for the complete depletion of GLU (2 d, P > 0.05) and GAL (3 d, P > 0.05), and that GLU+GAL consumption was significantly faster in the presence of K. marxianus (3 d, P < 0.05). On the other hand, B. claussenii exhibited significant differences in sugar utilization while in LAC vs GLU+GAL, not completing the fermentation for the latter (P < 0.05); a phenomenon that will be explored further. These results provide a deeper understanding of dairy sugar utilization by relevant yeast, allowing for future work to optimize fermentations to improve valued-added beverage and ingredient production from AW.

Keywords: acid whey, fermentation, ethanol.