We isolated two Candida pseudointermedia strains from the Atlantic rain forest in Brazil, and analyzed cellobiose metabolization in their cells. After growth in cellobiose medium, both strains had high intracellular β-glucosidase activity [~ 200 U (g cells)-1 for 200 mM cellobiose and ~ 100 U (g cells)-1 for 2 mM pNPβG] and negligible periplasmic cellobiase activity. During batch fermentation, the strain with the best performance consumed all the available cellobiose in the first 18 h of the assay, producing 2.7 g L-1 of ethanol. Kinetics of its cellobiase activity demonstrated a high-affinity hydrolytic system inside cells, with Km of 12.4 mM. Our data suggest that, unlike other fungal species that hydrolyze cellobiose extracellularly, both analyzed strains transport it to the cytoplasm, where it is then hydrolyzed by high-affinity intracellular β-glucosidases. We believe this study increases the fund of knowledge regarding yeasts from Brazilian microbiomes.
Keywords: Atlantic rain forest; Cellobiase; Fermentation; Hydrolysis; Yeast; β-Glucosidase.