Imobilização de biocatalisadores para hidrólise enzimática de materiais lignocelulósicos
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2019-02-26
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Universidade Federal de Goiás
Resumo
In the present work, different strategies of cellulases immobilization were studied. The
strategy that showed better cost-benefit was chosen for further optimization. The enzymatic
cocktail employed in this study was the Cellic Ctec 3 produced by Novozymes. One of the
main challenges was to immobilize in a non-selective way, the greatest possible number of
the (at least) 17 enzymes present in the cocktail, since they have different molecular masses,
types and number of functional groups on their surface. It’s worth mentioning that the
absence of one of these enzymes may prevent the complete conversion of the cellulose into
glucose. Cellulases immobilized by both cross-linking and covalent attachment on
glutaraldehyde-activated chitosan gel as well as sequential immobilization of β-glycosidase
(nucleus) and cellulases (periphery) had their performances evaluated in the hydrolysis of
sugarcane bagasse pretreated by an Organosolv process. Cellulases immobilized by covalent
attachment on glutaraldehyde activated chitosan gel presented the best results. A preliminary
study was necessary to develop a methodology to obtain the sequential immobilized β-
glycosidase, since the use of this methodology for hydrolysis of lignocellulosic materials
represents a great scientific innovation. Reaction parameters such as chitosan concentration
in gel preparation (0.5% to 2%), pH (7 to 10), immobilization time (10 to 120 minutes) and
enzyme loading (40.2 to 1340 mg protein / g support) were evaluated. Cellulases immobilized
at pH 9.0 for 30 minutes exhibited better hydrolysis performance when an enzyme loading of
134 milligrams per gram of support was used. Hydrolysates with a glucose content of 13.43
and 10.35 g / L were obtained when micro fibrillated avicel and pre-treated sugarcane
bagasse were used as substrate, respectively. The immobilized cellulase lost 60% of its
hydrolysis performance after 8 cycles of application using microfiber avicel as substrate. The
loss was 75% after 6 cycles of application when sugarcane bagasse was used. The great
hydrolysis performance associated with the successful reuse of the immobilized cellulases
indicates that the improvement of both immobilization methodology and pretreatment of
lignocellulosic biomass is able to generate cellulose with a high degree of purity, which will
allow the development of a continuous system of enzymatic hydrolysis with retained enzyme
in the reactor.
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PEREIRA, M. B. Imobilização de biocatalisadores para hidrólise enzimática de materiais lignocelulósicos. 2019. 74 f. Dissertação (Mestrado em Engenharia Química) - Universidade Federal de Goiás, Goiânia, 2019.