RESUMO
The use of appropriate yeast strains allows to better control the fermentation during beverage production. Bee products, especially of stingless bees, are poorly explored as sources of fermenting microorganisms. In this work, yeasts were isolated from honey and pollen from Tetragonisca angustula (Jataí), Nannotrigona testaceicornis (Iraí), Frieseomelitta varia (Marmelada), and honey of Apis mellifera bees and screened according to morphology, growth, and alcohol production. Bee products showed to be potential sources of fermenting microorganisms. From 55 isolates, one was identified as Papiliotrema flavescens, two Rhodotorula mucilaginosa, five Saccharomyces cerevisiae, and nine Starmerella meliponinorum. The S. cerevisiae strains were able to produce ethanol and glycerol at pH 4.0-8.0 and temperature of 10-30 °C, with low or none production of undesirable compounds, such as acetic acid and methanol. These strains are suitable for the production of bioethanol and alcoholic beverages due to their high ethanol production, similar or superior to the commercial strain, and in a broad range of conditions like as 50% (m/v) glucose, 10% (v/v) ethanol, or 500 mg L-1 of sodium metabisulfite.
Assuntos
Bebidas Alcoólicas/microbiologia , Mel/microbiologia , Pólen/microbiologia , Leveduras/isolamento & purificação , Ácido Acético/análise , Ácido Acético/metabolismo , Animais , Abelhas , DNA Espaçador Ribossômico , Etanol/análise , Etanol/metabolismo , Fermentação , Genes Fúngicos , Glicerol/análise , Glicerol/metabolismo , Rhodotorula/genética , Rhodotorula/isolamento & purificação , Rhodotorula/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/isolamento & purificação , Saccharomyces cerevisiae/metabolismo , Leveduras/genética , Leveduras/metabolismoRESUMO
Eight yeast isolates identified as Saccharomyces cerevisiae were recovered from molasses-using Cuban distilleries and discriminated by nucleotide sequence analysis of ITS locus. The isolates L/25-7-81 and L/25-7-86 showed the highest ethanol yield from sugarcane juice, while L/25-7-12 and L/25-7-79 showed high ethanol yield from sugarcane molasses. The isolate L/25-7-86 also displayed high fermentation capacity when molasses was diluted with vinasse. In addition, stress tolerance was evaluated on the basis of growth in the presence of inhibitors (acetic acid, lactic acid, 5-hydroxymethylfurfural and sulfuric acid) and the results indicated that L/25-7-77 and L/25-7-79 congregated the highest score for cross-tolerance and fermentation capacity. Hence, these isolates, especially L/25-7-77, could serve as potential biological platform for the arduous task of fermenting complex substrates that contain inhibitors. The use of these yeasts was discussed in the context of second-generation ethanol and the environmental and economic implications of the use of vinasse, saving the use of water for substrate dilution.