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Browsing by Author "Slama, Rym"

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  • Study of Saccharomyces cerevisiae growth: screen the best conditions and evaluate the effects of wine and histamine
    Publication . Slama, Rym; Dias, L.G.; Estevinho, Leticia M.
    The rowanberries (Sorbus aucuparia, also called Tramazeira fruits in Portugal) are small orange-red “fruits” of a rowan tree, which are highly resistant to cold climates. They have been traditionally used in various processed foods due to their high relevance to human health. These berries have been described as an important source of phenolic compounds and a source of bacteria/yeasts, being suitable for the production of health-food products. In this work, the microbiology quality of Tramazeira fruit samples was evaluated to select the one with higher microbial quality that could be used to isolate/select a yeast for further assays. After yeast identification as Saccharomyces cerevisiae (API method), an experimental design was applied to define optimal experimental conditions in a culture media for its growth. For this purpose, a fractional factorial design with 4 factors, 3 levels (including the center points) was applied varying the culture medium composition in glucose (10, 15 and 20 g/L), peptone (5, 7.5 and 10 g/L) and yeast extract (1, 3 and 5 g/L), as well, the inoculum quantity (105 , 106 and 107 CFU/mL). The optimal culture media (standard media) had 10 g/L of glucose, 5 g/L of peptone, 1 g/L of extract yeast, and 107 CFU/mL of inoculum quantity, which allowed to obtain a growth value of 22.8 CFU, in logarithmic scale. To test Saccharomyces cerevisiae growth, different matrices as grape juice or a mixture of grape juice and white wine (1:1), together with different concentrations of histamine (2, 5, 10, and 20 mg/L), were tested. It was shown that the Saccharomyces cerevisiae growth was delayed in the culture media with the presence of alcohol. Also, there was no evidence that histamine levels did affected the overall of Saccharomyces cerevisiae growth. Considering the overall results, there was a reduction in growth in the culture medium prepared with grape juice in comparison to the standard culture media (85.3% of the result obtained in the standard media), while for the culture medium with the mixture of grape juice and white wine, the growth was 67.0% of the standard media.
    2022Master thesis Open access Show more