Hidrólise de quitosana a partir de quitosanases e enzimas não-específicas imobilizadas
Chitooligosaccharides (COS) are products of the chitosan hydrolysis, which are high value-added because of their biological activities. The chitosan hydrolysis can be catalyzed by acid, although this method requires high temperature and does not have a large selectivity regarding the size of the...
Kaydedildi:
| Yazar: | |
|---|---|
| Diğer Yazarlar: | |
| Materyal Türü: | Dissertação |
| Dil: | pt_BR |
| Baskı/Yayın Bilgisi: |
Brasil
|
| Konular: | |
| Online Erişim: | https://repositorio.ufrn.br/jspui/handle/123456789/28241 |
| Etiketler: |
Etiketle
Etiket eklenmemiş, İlk siz ekleyin!
|
| Özet: | Chitooligosaccharides (COS) are products of the chitosan hydrolysis, which are
high value-added because of their biological activities. The chitosan hydrolysis can be catalyzed
by acid, although this method requires high temperature and does not have a large selectivity
regarding the size of the COS chains, a key feature for the expression of biological activities.
Alternatively, the use of enzymes as catalysts for the hydrolysis becomes an interesting option
because it requires mild conditions and the enzymes cleave specific bonds. However, processes
involving enzymes are quite costly, so it is necessary to implement strategies to reduce the
operational costs. Among these strategies, the immobilization of enzymes stands out as a
technique that usually increases thermal and pH stability, besides allowing enzyme recycle. The
use of non-specific enzymes can be highlighted as another strategy. Thus, the present study
investigated the immobilization of cellulase, β-glucosidase, and chitosanases for chitosan
hydrolysis. Prior to this study, the chitosanolytic activity of non-specific enzymes was evaluated
under different conditions. The highest activity for cellulase was obtained at pH 6.0 , whereas
for β-glucosidase, at pH 4.0, both at 55 oC. In order to evaluate the potential of the
immobilization techniques, experiments were carried out with adsorption on the cationic resin
Streamline SP and covalents bonds on silica-gel microparticles activated with glutaraldehyde.
Regarding the adsorption, pH 5.0 favored the immobilization of all enzymes, and in terms of
enzyme load, cellulase and quitosanase were favored by the lowest enzymatic load (25 U/g)
while β-glucosidase was favored by the highest enzymatic load (50 U/g). When analyzing the
covalent bond assays, the enzymes followed the same trend for enzimatic load, while in terms
of glutaraldehyde concentration, cellulase and β-glucosidase were favoured by the highest
concentration (1.00%), while the chitosanase yielded the best result with the lowest
concentration (0.50%). It is noteworthy that thermal stability, pH, and recycle tests were
performed to determine the best immobilization strategy for each enzyme. Thus, the best
immobilization strategy for cellulase and β-glucosidase was the covalent bonds, compared to
the adsorption, since it favored the stability of both enzymes during recycles (conserving
40.00% of the initial activity, compared to 20.00% of adsorption for cellulase, and 14.75%
against only 5.75% in the adsorption system for β-glucosidase). Finally, both immobilization
strategies succeeded in increasing the stability of the chitosanase, but adsorption showed a
marked increase in performance compared to the covalent bond strategy, maintaining 65.00%
of the initial activity at the end of the recycles against 44.42% for the covalent system. In
conclusion, all three immobilized enzymes were successful in chitosan hydrolysis. |
|---|