Fermentação de carboidratos por Meyerozyma Caribbica em microaerobiose

Abstract

Brazil is the second largest producer of ethanol in the world, but its production is almost entirely first generation, obtained through the fermentation of the sucrose contained in the sugarcane juice and/or molasses by the yeast Saccharomyces cerevisiae. Thus, the viability of the production of second-generation (2G) ethanol may further increase Brazilian production, however, in this case, it is necessary to ferment lignocellulosic raw materials composed of different sugars that S. cerevisiae is not capable of fermenting. In this context, it is extremely desirable to characterize other yeast species in order to select the most appropriate strains for the new process. In order to know the fermentative performance of the Meyerozyma caribbica species in relation to the main sugars found in lignocellulosic hydrolysates, the fermentation profiles of four strains of this yeast were evaluated under microaerobiosis condition in media containing alternately glucose, xylose or cellobiose as carbon sources. For this end, cellular biomass, sugar consumption and the ethanol production by these strains were analyzed during 12 hours of incubation. The analyzed yeasts consumed all the glucose during the incubation period and efficiently fermented this hexose, presenting fermentative yield equivalent to the theoretical maximum. On the other hand, xylose and cellobiose were not consumed by the cells during the period evaluated, thus making it impossible to produce ethanol from these carbohydrates. Thus, despite the inability to metabolize the pentose and the disaccharide tested under microaerobic conditions, the data demonstrate high fermentative efficiency of the analyzed yeasts against glucose, the main sugar in lignocellulosic hydrolysates.