Aplicação de diferentes estratégias de pré-tratamento para conversão da fibra de coco verde em etanol celulósico
Large volumes of green coconut husk residues are generated from the exploration of the fruit. Thus, arousing interest in the use of this lignocellulosic material as a raw material for the production of biofuels. Therefore, the present study evaluates the influence of different pre-treatments, aim...
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| 格式: | Dissertação |
| 語言: | pt_BR |
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Universidade Federal do Rio Grande do Norte
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| 在線閱讀: | https://repositorio.ufrn.br/handle/123456789/54353 |
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| 總結: | Large volumes of green coconut husk residues are generated from the
exploration of the fruit. Thus, arousing interest in the use of this lignocellulosic material as a
raw material for the production of biofuels. Therefore, the present study evaluates the
influence of different pre-treatments, aiming at using coconut fiber to obtain cellulosic
ethanol, being: sulfuric acid (H2SO4, 1% (v/v)) and steam explosion, as well as their
combination (combined pre-treatments) with sodium hydroxide (NaOH, 1 and 4% (m/v)) and
alkaline hydrogen peroxide (H2O2, 3 and 6% (m/v)). Were also evaluated separate hydrolysis
and fermentation (SHF), simultaneous saccharification and fermentation (SSF), and semisimultaneous saccharification, and fermentation (SSSF) strategies using the enzyme cocktail
Cellic CTec2 and the yeast Saccharomyces cerevisiae (PE-2). The evaluation of the pretreatments was carried out based on the analysis of the chemical composition of the materials,
using High-Performance Liquid Chromatography (HPLC), Fourier Transform Infrared
Spectroscopy (FTIR), and X-Ray Diffraction (DRX) for the crystallinity index. HPLC was
also used to evaluate the sugars during the hydrolysis and fermentation processes. The results
of the chemical composition of the applied pre-treatments, indicated that the pre-treatment
with sulfuric acid followed by NaOH (4.0% m/v) (ACN4) which presented the greatest
increase in the cellulose content (74.4% ) and pre-treatment with a steam explosion followed
by NaOH (4.0% m/v) (EXPN4) which showed the highest level of delignification (25%)
compared to in natura biomass, in order to facilitate enzymatic attack during the hydrolysis
step. It is noteworthy that practically all the hemicellulose was hydrolyzed in the acid pretreatment, thus, a significant concentration of xylose (10.5 g/L) was recorded in its liquid fraction, which was higher than that of the steam explosion (2.53 g/L). The use of sulfuric acid pre-treatments and steam explosion were effective to remove the hemicellulose present in
the coconut fiber, but the enzymatic digestibility values of the combined pre-treated materials
were low (cellulosic conversion less than 50%). In the enzymatic hydrolysis, the enzymatic
cocktail Cellic CTec2 was used in different enzymatic loads (10,0, 15,0 and 20,0 FPU/g),
with the best results obtained for the load of 10.0 FPU/g for using the ACN4 pre-treatment
and 15.0 FPU/g for the EXPN4 pretreatment, with cellulosic conversions 48.68 ± 1.98% and
50.24 ± 2.87%, glucose content 15.59 ± 0.63 g/L and 13.28 ± 0.75 g/L, for the ACN4 and
EXPN4 assays, respectively. Regarding the fermentation strategies that were carried out
varying the solid load, between 5% and 15% (m/v), the SSSF strategy, when using the acidalkaline pre-treatment with NaOH (4.0% m/v), showed a better result compared to SSF, with
a cellulosic ethanol yield of 46.67±2.31% and 18.37±0.91 g/L of ethanol. While HFS did not
show results regarding ethanol production. For all these reasons, green coconut fiber proved
to be suitable to be used to obtain second-generation ethanol (2G). |
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