Fisiologia de 15 leveduras em diferentes condições de cultivo

Abstract

Bioprospecting of new strains of yeasts is important because of the great biodiversity that exists in nature and still little explored. Brazilian Midwest Region due to its environmental characteristics are favorable to the presence of microorganisms, such as yeasts, being an environment conducive to the bioprospecting of new strains. In addition, the region has several plants and distilleries, in which during the fermentation process several of wild yeasts are present. The physiological study of new strains becomes important for the establishment of new microbial platforms with different biotechnological applications. The first chapter presents a general introduction about the work. The second chapter is a reviews the use of kinetic parameters as a tool for physiological studies in yeast. In the third chapter, the physiology of Saccharomyces cerevisiae CAT-1, 3 yeasts isolated from sugar and alcohol plants and 11 yeasts isolated from fruits of the Brazilian Cerrado were evaluated using fructose (10 g L-1) as the sole source of carbon, in aerobiosis. The strains that showed the highest specific maximum growth rate (μmax) were isolated from must (values between 0.47 and 0.49 h-1). Among the isolated strains of fruits, Candida parapsilosis Recol 29 presented higher μmax (0.44 h-1). S. cerevisiae CAT-1 (3.02 h-1), S. cerevisiae BB9 (3.01 h-1) and Candida glabrata Recol 41 (2.52 h-1) stood out in terms of μS. C. parapsilosis Recol 29 and Rhodotorula mucilaginosa Recol 03 were those that presented higher YX/S. YP/S analysis indicated that C. glabrata Recol 10 and S. cerevisiae BB9 stood out (0.44 and 0.41 gEth gS-1, respectively). Finally, in the fourth chapter the physiology of S. cerevisiae CAT-1 and other 13 yeasts isolated from the Brazilian Cerrado were analyzed using kinetic parameters obtained from cultures with 3 different single sources of carbon (glucose, fructose or sucrose) under anaerobic conditions. In glucose, S. cerevisiae CAT-1 showed the highest values of μmax (0.35 h-1), μS (3.06 h-1) and PEth (0.69 gEth L-1 h-1). Candida glabrata Recol 43 and C. glabrata Recol 10 were distinguished by the rapid consumption of substrate, formation of ethanol and biomass. Meyerozyma guilliermondii Recol 09, Candida parapsilosis Recol 12, Candida parapsilosis Recol 37 and Isolate Recol 42 showed longer culture time. As in glucose, S. cerevisiae CAT-1 was superior to the other fructose strains, with values higher than μmax (0.25 h-1), μS (2.24 h-1) and PEth (0.60 gEth L-1 h-1). M. guilliermondii Recol 09, C. parapsilosis Recol 37 and Isolate Recol 42 presented cultures with more than 30 h and residual substrate. In sucrose, only S. cerevisiae CAT-1, S. cerevisiae BB9 and Pichia kudriavzevii Recol 39 were able to consume the entire substrate presenting PEth of 0.72, 0.51 and 0.44 gEth L-1 h-1, respectively. It was observed in the experiments that fructose is an interesting substrate, because in anaerobiosis the yeasts showed higher ethanol formation in this substrate. In addition, different strains showed biotechnological potential.