Microbiologia
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/11840
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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 The high fermentative metabolism of Kluyveromyces marxianus UFV-3 relies on the increased expression of key lactose metabolic enzymes(Antonie van Leeuwenhoek, 2001-11-09) Diniz, Raphael H. S.; Silveira, Wendel B.; Fietto, Luciano G.; Passos, Flávia M. L.The aim of this work was to obtain insights about the factors that determine the lactose fermentative metabolism of Kluyveromyces marxianus UFV-3. K. marxianus UFV-3 and Kluyveromyces lactis JA6 were cultured in a minimal medium containing different lactose concentrations (ranging from 0.25 to 64 mmol l−1) under aerobic and hypoxic conditions to evaluate their growth kinetics, gene expression and enzymatic activity. The increase in lactose concentration and the decrease in oxygen level favoured ethanol yield for both yeasts but in K. marxianus UFV-3 the effect was more pronounced. Under hypoxic conditions, the activities of β-galactosidase and pyruvate decarboxylase from K. marxianus UFV-3 were significantly higher than those in K. lactis JA6. The expression of the LAC4 (β-galactosidase), RAG6 (pyruvate decarboxylase), GAL7 (galactose-1-phosphate uridylyltransferase) and GAL10 (epimerase) genes in K. marxianus UFV-3 was higher under hypoxic conditions than under aerobic conditions. The high expression of genes of the Leloir pathway, LAC4 and RAG6, associated with the high activity of β-galactosidase and pyruvate decarboxylase contribute to the high fermentative flux in K. marxianus UFV-3. These data on the fermentative metabolism of K. marxianus UFV-3 will be useful for optimising the conversion of cheese whey lactose to ethanol.