EFFECTS ON THE MINERAL COMPOSITION OF FLEISCHMANN’S YEAST (Saccharomyces cerevisiae) FERMENTING SUGAR-CANE JUICE CONTAMINATED WITH COBALT

Abstract

The current work aimed to study the accumulation and the effects of cobalt on themineral composition of Fleischmann’s yeast Saccharomyces cerevisiae fermentingsugarcane juice with controlled contamination, in sub-toxic levels of cobalt. Thesterilized juice (120°C, 20 minutes), with 12% of total reducing sugars (TRS) and fourlevels of pH (3.5; 4.5; 5.5 and 6.5) was added with cobalt chloride salt (CoCl2.6H2O)resulting in six levels of contamination (0.0; 0.1; 0.5; 1.0; 2.0 e 5.0 mg Co L-1) and 24treatments. The juice inoculation was carried out with bread yeast (10% p/p). Afterthe end of the fermentation (6 hours), the fermented media were centrifuged, and thecellular viability, budding rate and levels of cobalt, phosphorus, calcium, magnesium,sulfur, copper, iron, manganese, potassium and zinc were determined (in dry weight– dw). The absorption of cobalt was influenced by the pH. This absorption was higherin pH 3.5, whereas in pH 6.5 we found almost no absorption. The levels ofpotassium, calcium, zinc and phosphorus decreased with the increase of pH whilethe levels of sulfur content increased. No significant differences could be observed inthe fermentative velocity for the several treatments.