Immobilization of a recombinant endo-1,5-arabinanase secreted by Aspergillus nidulans strain A773

An endo-1,5-arabinanase (abnA) encoding gene from Aspergillus niveus was identified, cloned and successfully expressed in Aspergillus nidulans strain A773. Based on amino acid sequence comparison, the 34-kDa enzyme could be assigned to CAZy GH family 43. Characterization of purified recombinant endo-1,5-arabinanase (AbnA) revealed that it is active at a wide pH range (pH 4.0–7.0) and an optimum temperature at 70 °C. The immobilization of the AbnA was performed via covalent binding onto agarose-modified supports: glyoxyl iminodiacetic acid–Ni2+, glyoxyl amine, glyoxyl (4% and 10%) and cyanogen bromide activated sepharose. The yield of immobilization was similar on glyoxyl amine and glyoxyl (96%), and higher than glyoxyl iminodiacetic acid–Ni2+ (43%) support. The thermal inactivation of these immobilized preparations showed that the stability of the AbnA immobilized on glyoxyl 4 and 10% was improved by 4.0 and 10.3-fold factor at 70 °C. The half-life of glyoxyl 4% derivative at 60 °C was >48 h (pH 5), 9 h (pH 7) and 88 min (pH 9). The major hydrolysis product of debranched arabinan or arabinopentaose by glyoxyl agarose-immobilized AbnA was arabinobiose.

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► pEXPYR plasmids carrying abnA gene was transformed into A. nidulans strain A773.
► The AbnA was successfully over-secreted to culture medium by maltose induction.
► Purified recombinant AbnA was immobilized in modified agarose supports.
► 10% glyoxyl agarose derivative was 10.3-fold more stable than the free enzyme at 70 °C.
► Arabinotriose and arabinobiose were the major AbnA hydrolyses products from arabinan.