QUANTIFICAÇÃO DO METABOLISMO RESPIROFERMENTATIVO DE LEVEDURAS DE CERVEJA, VINHO E PÃO POR MÉTODO ESTEQUIOMÉTRICO

The alcoholic yeast can breathe and ferment simultaneously, called respiro-fermentative metabolism.  Yeast’s respiration and fermentation metabolism can be measured considering the amount of ethanol produced in the fermentation process and the carbon dioxide produced in both respiration and fermentation processes. This research focused on calculating the respiration and fermentation rates of five different alcoholic yeast strains (baker’s, beer top-fermenting (ale), beer bottom fermenting (lager), red wine and white wine) by stoichiometry. Sugar cane must (15 °Brix) was used as growth medium. Fermentation was performed in an open vessel at room temperature. A sample was taken hourly, and the fermentation process ended after 8 hours. Beer top-fermenting yeast and baker’s yeast resulted in higher respiration rates (19.17% and 19.12%), while white wine yeast and bottom-fermenting yeast resulted in higher fermentation rates (90.48% and 89.67%). Bottom-fermenting yeast produced higher amount of ethanol (7.57%) and baker’s yeast presented higher metabolic activity (131.59 g of sucrose consumed).