L-asparaginase (ASNase, EC 3.5.1.1) is an enzyme that catalyzes L-asparagine hydrolysis into L-aspartic acid and
ammonia and is mainly applied in pharmaceutical and food industries [1]. The ASNase currently commercialized for pharmaceutical purposes is produced from two main bacterial sources: recombinant Escherichia coli
and Erwinia chrysanthemi. However, some disadvantages are associated with its free form, such as the shorter
half-life [2]. Immobilization of ASNase has been proposed as an efficient approach to overcome this limitation
[3]. In this work, a straightforward method, including the functionalization of multi-walled carbon nanotubes
(MWCNTs) through a hydrothermal oxidation treatment with nitric acid, and the immobilization of ASNase
by adsorption over pristine and modified MWCNTs was investigated. Different operation conditions, including pH, contact time, ASNase/MWCNT mass ratio, and the operational stability of the immobilized ASNase were
evaluated. The characterization of the ASNase-MWCNT bioconjugate was addressed using different techniques,
namely Transmission Electron Microscopy (TEM), Thermogravimetric analysis (TGA), and Raman spectroscopy.
Functionalized MWCNTs showed promising results, with an immobilization yield and a relative recovered activity of commercial ASNase above 95%, under the optimized adsorption conditions (pH 8, 60 min of contact
and 1.5´10–3 g.mL-1of ASNase). The ASNase-MWCNT bioconjugate also showed improved enzyme operational
stability (6 consecutive reaction cycles without activity loss), proving its suitability for application in industrial
processes.publishe
