(Monday’s/9.30H/CEB anfitheatre)
Zlatina Genisheva, Production of white wine by Saccharomyces cerevisiae immobilized on grape pomace
White wine was produced with Saccharomyces cerevisiae cells immobilized on grape pomace, by natural adsorption. The support, the main solid waste from the wine industry, was constituted by skins, seeds and stems. Immobilization was tested using different media, namely complex culture medium, raw grape must and diluted grape must. Grape pomace revealed to be an appropriate support for yeast cells immobilization. Moreover, grape must showed to be the most suitable medium as immobilized cells became adapted to the conditions in the subsequent alcoholic fermentation in the winemaking process. The produced wines either with immobilized cells or with free cells, for comparison, were subjected to chemical analysis by HPLC (ethanol, glycerol, sugars and organic acids) and by gas chromatography (major and minor volatile compounds); additionally, color (CIELab) and sensory analysis were also performed.
Hector Ruiz, Process Development for Bioethanol Production Using Wheat Straw Biomass
Pre-doctoral defense
Nowadays, the role of biorefineries is centered on integration of traditional and modern processes for utilization of biological raw material in the production of energy and chemicals. Lignocellulosic materials such as wheat straw are renewable biomass than can be used as substrate in fermentation processes. The use of wheat straw includes the following steps: milling, pretreatment, enzymatic saccharification and bioconversion of the obtained sugars in bioethanol. In a first stage, autohydrolysis pretreatment was used for solubilization of hemicellulose. In a second stage, the pretreated solids obtained after autohydrolysis were subjected to delignification using organosolv process. A high purity lignin was obtained after the sequential autohydrolysis-organosolv process. Following the biorefinery philosophy, the autohydrolysis hemicellulose extracted by autohydrolysis optimum conditions was used as reinforcements in a polymeric matrix for biocomposite manufacturing. The susceptibility to enzymatic saccharification of pretreated solids obtained by autohydrolysis and by sequential autohydrolysis-organosolv was studied. The simultaneous saccharification and fermentation of lignocellulosic materials was evaluated. In order to evaluate the effects of temperature, substrate concentration (autohydrolysis pretreated wheat straw) and enzyme loading on: 1) ethanol conversion yield, 2) ethanol concentration, and 3) CO2 concentration, an experimental design was used. Results showed that the ethanol conversion yield was mainly affected by enzyme loading, whereas for ethanol and CO2 concentration, enzyme loading and substrate concentration were found to be the most significant parameters. The scale-up of SSF was performed evaluating the effect of stirring on ethanol yield. When the SSF was conducted at higher stirring speed (250 rpm), 84.49 % of ethanol yield was obtained. Overall, results presented in this work, describe the development of an integrated process based on the biorefinery concept for the production of bioethanol from wheat straw. It is shown that wheat straw pretreated with autohydrolysis process can be used as a substrate for bioethanol production using a flocculent S. cerevisiae strain.
