What are the characteristics of saccharomyces cerevisiae?
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Answer:
Invasive growth
The yeast strains were cultivated on YPD medium (10 g/L yeast extract; 20 g/L peptone; 20 g/L glucose; 20 g/L agar) at 30 °C for 3 days, followed by incubation at room temperature for 2 days. The Petri dishes were photographed, and afterwards, the agar surface was washed with distilled water to remove colonies. The dishes were photographed again to verify the presence of colony spots in the agar (a sign of invasive growth into the culture medium). Spots were excised from the agar, placed on slides with water, and coverslipped, and filamentous structures were visualized with an optical microscope at 100× magnification.
Flocculation
The flocculation assay was performed according to Wang et al. (2008), with some modifications. After growth in the multiplication medium (sugar cane juice with around 4% of reducing sugars), the cells were collected by centrifugation, washed twice with sodium citrate buffer (50 mM; pH 3.0) containing 5 mM EDTA and washed again with water at 4 °C. The cells were resuspended in cold distilled water and diluted or concentrated until an OD (600 nm) of 2.0 was reached (Thermo Biomate® spectrophotometer). Flocculation (sedimentation) of the cells was determined in the absence or presence of calcium chloride (10 mM). After vigorous shaking, samples from the upper portion of the tube were taken at 0 and after 10 min, and the OD was determined. The flocculation percentage (%) was calculated as follows: Flocculation (%) = [(OD0min − OD10min) × 100] / OD0min.