Navegando por Autor "Rodrigues, Marina Q. R. B."
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Item Optimizing and validating the production of ethanol from cheese whey permeate by Kluyveromyces marxianus UFV-3(Biocatalysis and Agricultural Biotechnology, 2014-04) Diniz, Raphael H. S.; Rodrigues, Marina Q. R. B.; Fietto, Luciano G.; Passos, Flávia M. L.; Silveira, Wendel B.The purpose of this study was to optimize the production of ethanol from cheese whey permeate using Kluyveromyces marxianus UFV-3. We used the response surface methodology (RSM) with a central composite rotational design (CCRD) to evaluate the effects of pH (4.5–6.5), temperature (30–45 °C), lactose concentration (50–250 g l^−1), and cell biomass concentration (A600 2–4). We performed 29 fermentations under hypoxia in cheese whey permeate and seven fermentations for the validation of the equation obtained via RSM. Temperature was the most significant factor in optimizing ethanol production, followed by pH, cell biomass concentration and lactose concentration. The conditions for producing ethanol at yields above 90% were as follows: temperature between 33.3 and 38.5 °C, pH between 4.7 and 5.7, cell biomass concentration between A600 2.4 and 3.3, and lactose concentration between 50 and 108 g l^−1. The equation generated from the optimization process was validated and exhibited excellent bias and accuracy values for the future use of this model in scaling up the fermentation process.Item Physiological characterization of thermotolerant yeast for cellulosic ethanol production(Applied Microbiology and Biotechnology, 2014-02-18) Costa, Daniela A.; Souza, Carlos J. A. de; Costa, Patrícia S.; Rodrigues, Marina Q. R. B.; Santos, Ancély F. dos; Lopes, Mariana R.; Genier, Hugo L. A.; Silveira, Wendel B.; Fietto, Luciano G.The conversion of lignocellulose into fermentable sugars is considered a promising alternative for increasing ethanol production. Higher fermentation yield has been achieved through the process of simultaneous saccharification and fermentation (SSF). In this study, a comparison was performed between the yeast species Saccharomyces cerevisiae and Kluyveromyces marxianus for their potential use in SSF process. Three strains of S. cerevisiae were evaluated: two are widely used in the Brazilian ethanol industry (CAT-1 and PE-2), and one has been isolated based on its capacity to grow and ferment at 42 °C (LBM-1). In addition, we used thermotolerant strains of K. marxianus. Two strains were obtained from biological collections, ATCC 8554 and CCT 4086, and one strain was isolated based on its fermentative capacity (UFV-3). SSF experiments revealed that S. cerevisiae industrial strains (CAT-1 and PE-2) have the potential to produce cellulosic ethanol once ethanol had presented yields similar to yields from thermotolerant strains. The industrial strains are more tolerant to ethanol and had already been adapted to industrial conditions. Moreover, the study shows that although the K. marxianus strains have fermentative capacities similar to strains of S. cerevisiae, they have low tolerance to ethanol. This characteristic is an important target for enhancing the performance of this yeast in ethanol production.Item Production and Characterization of β-Glucanase Secreted by the Yeast Kluyveromyces marxianus(Applied Biochemistry and Biotechnology, 2014-01-04) Lopes, Mariana R.; Souza, Carlos J. A. de; Rodrigues, Marina Q. R. B.; Costa, Daniela A.; Santos, Ancély F. dos; Oliveira, Leandro L. de; Ramos, Humberto J. O.; Guimarães, Valéria M.; Silveira, Wendel B.; Passos, Flávia M. L.; Fietto, Luciano G.An extracellular β-glucanase secreted by Kluyveromyces marxianus was identified for the first time. The optimal conditions for the production of this enzyme were evaluated by response surface methodology. The optimal conditions to produce β-glucanase were a glucose concentration of 4 % (w/v), a pH of 5.5, and an incubation temperature of 35 °C. Response surface methodology was also used to determine the pH and temperature required for the optimal enzymatic activity. The highest enzyme activity was obtained at a pH of 5.5 and a temperature of 55 °C. Furthermore, the enzyme was partially purified and sequenced, and its specificity for different substrates was evaluated. The results suggest that the enzyme is an endo-β-1,3(4)-glucanase. After optimizing the conditions for β-glucanase production, the culture supernatant was found to be effective in digesting the cell wall of the yeast Saccharomyces cerevisiae, showing the great potential of β-glucanase in the biotechnological production of soluble β-glucan.