Método simples para quantificar o metabolismo aeróbio e anaeróbio de levedura alcoólica

Abstract

The objective of this work was to quantify aerobic (respiration) and anaerobic (alcoholic fermentation) metabolisms of yeasts during the fermentation of two musts made from sugarcane or molasses by using one simple stoichiometric method. The experiment was conducted on three treatments (soluble solids content for the musts) and three repetitions adding up to nine parcels for each type of must (molasses and sugarcane juice). Molasses were diluted into water producing musts with 10, 20 e 30 °Brix, while for sugarcane either water or granulated sugar was added to the juice for the same purpose. Musts were inoculated using dry bakery yeast (100 g/L) and let to ferment under room temperature. CO2 and ethanol masses were determined throughout all the fermentation to quantify metabolized sugars (fermented and respired), using stoichiometric calculations. Results showed that during the process, yeasts catabolized sugar by both aerobic and anaerobic pathways, whereas the anaerobic prevailed. Fermentation rate, for the molasses must, ranged from 80.02% (10 °Brix) to 91.58% (30 °Brix) while for the sugarcane, from 83.17% (10 °Brix) to 89.16% (30 °Brix), which indicates that the Crabtree effect was present.