Biochemical studies on immobilized fungal β-glucosidase

Abstract

-β-Glucosidase from Aspergillus niger was immobilized on sponge by covalent binding through a spacer group (glutaraldehyde). Sponge-immobilized enzyme had the highest immobilization yield (95.67%) and retained 63.66% of the original activity exhibited by the free enzyme. The optimum pH of the immobilized enzyme remains almost the same as for the free enzyme (pH 4.0). The optimum temperature for β-glucosidase activity was increased by 10 ºC after immobilization. The activation energy (E a ) of the immobilized β-glucosidase was lower than the free enzyme (3.34 and 4.55 kcal/mol), respectively. Immobilized β-glucosidase exhibited great thermal stability and retained all the initial activity after incubation at 55 ºC for 2 h; however, the free enzyme retained 89.25% under the same condition. The calculated half-life (t ½ ) value of heat inactivation of immobilized enzyme at 60, 65 and 70 ºC was 213.62, 72.95 and 56.80 min, respectively, whereas at these temperatures the free enzyme was less stable (half-life of 200.0, 55.31 and 49.5 min, respectively). The deactivation rate constant at 65 ºC for the immobilized β-glucosidase is 9.5x10 -3 / min, which was lower than that of the free form (12.53x10 -3 / min). The immobilization process improved the pH stability of the enzyme (immobilized and free enzyme retained 69.35 and 39.86%, respectively, of their initial activity after 45 min at pH 7.5). The effect of some chemical substances on the activity of the immobilized and free β-glucosidase has been investigated. In the presence of sodium dodecyl sulfate (SDS) and p-chloromercuri benzoate (p-CMB) the immobilized enzyme retained 36.13 and 45.34%, respectively, of the initial activity, which is higher than that of free enzyme (13.71 and 1.61%, respectively). The Michaelis constant (K m ) value of the free enzyme was 40.0 mM, while the apparent K m value for the immobilized enzyme was 46.51 mM. The maximum reaction rate (v max ) of immobilized β-glucosidase was smaller than that of the free enzyme by 7.69%. Sponge-immobilized β-glucosidase was repeatedly used to hydrolyze cellobiose (5 and 8 cycles with retained activity of 67.32 and 51.04%, respectively).

Hybrid Nanomaterials of Magnetic Iron Nanoparticles and Graphene Oxide as Matrices for the Immobilization of β-Glucosidase: Synthesis, Characterization, and Biocatalytic Properties

“…enzyme was observed at pH 5.0; a similar pH profile has been reported for the immobilization of bgl on iron magnetic nanoparticles (Abraham et al, 2014), while other studies demonstrated that immobilized bgl on magnetic nanoparticles reaches its maximum activity at pH 4.0 (Ahmed et al, 2013;Zhou et al, 2013). In most cases, the immobilized bgl was found to keep its activity in a pH range from 2.5 to 5.0, indicating that the immobilized enzyme is less sensitive to the modification of the pH than the free enzyme.…”

“…This proves that the covalent immobilization of bgl onto magnetic nanoparticles, functionalized GO, and GO-magnetic nanoparticle hybrids results in more stable biocatalysts as compared to the native soluble enzyme. A similar improvement of the stability of bgl has been reported previously, where different materials were used for the covalent immobilization of the enzyme (Ahmed et al, 2013). The observed improvement in the thermal stability of immobilized bgl comparing to the free enzyme may result from the combined action of a reduced molecular mobility and an improved conformational stabilization of the enzyme induced by the covalent bonding of bgl to the nanomaterials (Figueira et al, 2011;Patila et al, 2016a).…”

Characterization and Immobilization of A Novel Hyaluronidase Produced By Streptomyces roseofulvus

“…The Tm value for the free hyaluronidase and Ca-alginate hyaluronidase were 24.7 and 46.1°C, respectively. These results indicated that, the immobilized enzyme was highly stable in comparison to the free form (Ahmed et al, 2013;Reda et al, 2018 a,b). Ahmed et al (2007) reported that the immobilized Egypt.…”

“…Ortega et al (1998) reported that entrapped β-glucosidase of Saccharomyces cerevisiae in alginate and polyacrylamide retained its activity of about 66.0%. Ahmed et al (2013) reported that Aspergillus niger β-glucosidase immobilized onto sponge showed the highest immobilized yield compared with its immobilized in agarose.…”

Production of Microcapsules used in Bioremediation and Plant Growth Support

“…Przykładowo chitozan był wykorzystany (przez Skoronskiego i współautorów) do adsorpcyjnej immobilizacji laktazy, następnie przeprowadzono sieciowanie z wykorzystaniem aldehydu glutarowego. Otrzymany produkt został wykorzystany do rozkładu związków fenolowych z wydajnością przekraczającą 90%, która możliwa była do osiągnięcia nawet po okresie magazynowania [14]. Wśród nieorganicznych nośników stosowane są: krzemionki, szkło porowate, węgiel aktywny.…”