Journal of Materials Research and Technology (Sep 2021)
Modified magnetite nanoparticle as biocatalytic support for magnetically stabilized fluidized bed reactors
Abstract
Magnetically stabilized fluidized bed reactor (MSFBR) is a sustainable and cost-effective biotechnological process, which justifies the increasing search for biocatalytic superparamagnetic supports to enzyme immobilization. This work, investigates the effect of modified nanomagnetite, Fe3O4 (nM), for biocatalytic support on properties associated with catalytic behavior and potential use in MSFBR. The nM was either synthesized and then modified with 3-aminopropyltriethoxysilano (nM-APTES) or stabilized with oleic acid (nM-OA) and later modified with chitosan (nM-OA-Cs). A novel correlation study was carried out about the support dimension effect, enzymatic surface loading and retained activity. Both nM-based supports were morphologically, structurally and magnetically characterized by X-ray diffraction, thermogravimetry, Mössbauer and Fourier-transform Infrared spectroscopies, as well as vibration sample magnetometry, scanning (SEM) and transmission (TEM) electron microscopies. The nM-APTES and nM-OA samples disclosed crystal sizes of 8.07 and 8.69 nm, respectively. From TEM imagens, the average particles sizes were 10.9 nm for nM-APTES and 12.6 nm for nM-OA. The nM-OA-Cs displayed an average particles size of 918.6 μm. These magnetic supports displayed high saturated magnetization, 79.6 emu/g for nM-APTES and 72.7 emu/g for nM-OA. The amano lipase AK enzyme was immobilized on supports activated with glutaraldehyde. The enzyme loading density of nM-APTES-GA-Lip (122 mg/g) with 61% immobilization yield was higher than that of nM-OA-Cs-GA-Lip (46 mg/g) with 23% immobilization yield. The catalytic activity of nM-APTES-GA-Lip (85%) was higher than that of nM-OA-Cs-GA-Lip (46%), which reflected the correlation between enzyme loading efficiency on the magnetic nanosupports and their relative activity, essential to potential use in MSFBR.
