5-Hydroxymethylfurfural induces ADH7 and ARI1 expression in tolerant industrial Saccharomyces cerevisiae strain P6H9 during bioethanol production.

The aims of this work were to obtain, by evolutionary engineering, an industrial strain of Saccharomyces cerevisiae tolerant to high concentrations of HMF and to determine the expression levels of genes previously described as responsible for this tolerance. Cells were grown under anaerobic and oxygen limited conditions, in the presence of glucose or sucrose as carbon sources. P6H9 strain presented high expression levels for genes ADH7 and ARI1 in presence of HMF. This tolerant strain also showed higher ethanol productivity, biomass formation and alcohol dehydrogenase activity comparing to sensitive strains. Results suggest that S. cerevisiae P6H9 strain presents potential to be used for second-generation ethanol production.

Conversion of sugars present in rice hull hydrolysates into ethanol by Spathaspora arborariae, Saccharomyces cerevisiae, and their co-fermentations.

The production of ethanol by the new yeast Spathaspora arborariae using rice hull hydrolysate (RHH) as substrate, either alone or in co-cultures with Saccharomyces cerevisiae is presented. Cultivations were also carried out in synthetic medium to gather physiological information on these systems, especially concerning their ability to grow and produce ethanol in the presence of acetic acid, furfural, and hydroxymethylfurfural, which are toxic compounds usually present in lignocellulosic hydrolysates. S. arborariae was able to metabolize xilose and glucose present in the hydrolysate, with ethanol yields (Y(P/S)(et)) of 0.45. In co-cultures, ethanol yields peaked to 0.77 and 0.62 in the synthetic medium and in RHH, respectively. When the toxic compounds were added to the synthetic medium, their presence produced negative effects on biomass formation and ethanol productivity. This work shows good prospects for the use of the new yeast S. arborariae alone and in co-cultures with S. cerevisiae for ethanol production.

Cellulase production by Penicillium echinulatum on lactose.

The inducer effect of lactose on cellulase activity in Penicillium echinulatum 9A02S1 was studied. Submerged cultivation was performed using different concentrations of lactose and cellulose, in which the pH, mycelial mass, soluble proteins, filter paper activity (FPA), and activity of beta-glucosidases were measured. The cultures containing lactose only presented low FPAs (0.1 FPU/ml). The cultures with associated cellulose and lactose and those containing cellulose only presented similar enzymatic activities (1.5 FPU/ml), suggesting the possibility of up to 75% reduction in the cellulose concentration. In relation to the beta-glucosidases, increasing the lactose/cellulose ratio results in a proportional increase of enzymatic activity. In the cultures using both inducers, there is a longer duration of the acid phase in relation to treatments using only cellulose or lactose, indicating diauxia and catabolic repression.