Caracterização e avaliação do potencial biotecnológico de leveduras da cana-de-açúcar

Abstract

The yeasts found during the fermentation of sugarcane juice are still little known in relation to their biotechnological potential. In this perspective, the present work aimed to morphologically characterize yeasts isolated from sugarcane must and to evaluate the growth capacity at different temperatures, carbon sources and concentrations of acetic acid and ethanol, as well as the production of hydrogen sulfide. Seven yeasts were reactivated and characterized macro and micromorphologically. For the growth test at different temperatures, the yeasts were inoculated in YPDA (Yeast Peptone Dextrose Agar) and incubated at 4°C, 15°C, 20°C, 25°C, 30°C, 37°C and 40°C. To evaluate growth on different carbon sources, YPD (Yeast Peptone Dextrose) + specific carbon source (fructose, sucrose, maltose, galactose, lactose and xylose) were used. For the hydrogen sulfide production test, a specific medium called LA was used. To verify the tolerance of yeasts to acetic acid and ethanol, concentrations of 10, 15 and 20% were used and after 72h of incubation, growth and effective growth were evaluated based on absorbance measurements at 600 nm at times 0 and 72h in the spectrophotometer. The yeasts showed morphological similarities in terms of elevation and white color, and morphological differences in terms of shape, margins, surface, diameter and size of the colonies. In the micromorphological characterization, ellipsoidal, subglobose and oval cells with pseudohypha formation were observed in yeasts A and E. All yeasts showed a satisfactory growth rate at temperatures of 15ºC, 20ºC and 30ºC. At 37°C only yeasts A, B and D grew well and at 40°C only yeasts B and D did. All yeasts grew in the presence of fructose. Yeast A, B, D and G grew using sucrose, galactose, lactose and xylose as carbon sources. Yeasts A, D, E and F did not show formation of hydrogen sulfides. Only yeast C showed cell growth in the three concentrations of acetic acid (10%, 15%, 20%), while, for the ethanol test, only yeast B showed cell growth at a concentration of 20%. Of the seven yeasts used in the study, yeasts A, B and D stood out in most stages. These results indicate a possible biotechnological potential of yeasts isolated from must, however more studies need to be conducted.