Enhanced biocatalytic sustainability of laccase by immobilization on functionalized carbon nanotubes/polysulfone membranes

Abstract

Chemically functionalized multi-walled carbon nanotubes (CNTs) are used as carriers for laccase immobilization. In this work, CNTs were modified using different approaches with a combination of methods involving hydrothermal oxidation with nitric acid, treatment with 3-aminopropyltriethoxysilane, glutaraldehyde, N-ethyl-N-(3-(dimethylamino)-propyl) carbodiimide hydrochloride and N-hydroxysuccinimide. The enzyme immobilization efficiency and recovered activity were evaluated towards-azino-bis(3-ethylbenzathiazoline-6-sulfonic acid) biocatalytic oxidation. The best compromise between immobilization efficiency and recovered activity was obtained using the CNTs functionalized with 0.3 M HNO 3 , treated with N-ethyl-N-(3-(dimethylamino)propyl) carbodiimide hydrochloride and N-hydroxysuccinimide. This catalyst also showed the best thermal stability (at 50 and 60 ºC). The bioconjugate based on this material was characterized by vibrational spectroscopies (FTIR and Raman) and by N 2 adsorption. The results from reutilization tests showed that laccase activity was kept above 65% of its initial value after five consecutive cycles of reuse. The biocatalytic performance of the immobilized enzyme was evaluated for the degradation of a mixture of phenolic compounds in water containing phenol, resorcinol, 4-methoxyphenol and 4-chlorophenol. As means of cost efficient to enzyme reutilization, laccase was immobilized over polysulfone membranes blended with the functionalized CNTs and studied in the degradation of 4-methoxyphenol.

Polymer-Assisted Biocatalysis: Polyamide 4 Microparticles as Promising Carriers of Enzymatic Function

“…All three samples showed no activity, leading to the conclusion that there is no residual laccase in the supernatant, therefore almost 100% of the enzyme was adsorbed upon the PA4 supports (Table 3). This was a superior immobilization efficiency as compared to previous studies disclosing laccase immobilization by covalent bonding on PA6 [21] or carbon nanotube supports [30] with immobilization effectiveness (IE) values of 59-71% or 60-90%, respectively. However, the lack of activity of the residual supernatant means that it is free of active laccase but could contain some amounts of inactive enzyme.…”

Development of Electrochemical Biosensor Based on Nanostructured Carbon Materials for Paracetamol Determination

“…The presence of a strong absorption band at 3440 cm À 1 was attributed to the stretch OÀ H groups involved in intramolecular bonding [22]. The band, characteristic of carbonaceous materials, was detected in 2855 cm À 1 and it can be assigned to the CÀ H stretch, while the band at 1600 cm À 1 is characteristic of À C=C-stretch [23].The band at 1544 cm À 1 occurs due to aromatic stretching vibration of side chain amino acids, confirming the presence of laccase in the composite [24], which suggest the efficient formation of MWCNT/LAC composite.…”

Wastewater Treatment by Novel Polyamide/Polyethylenimine Nanofibers with Immobilized Laccase

“…In order to utilize enzymes for industrial applications, it is necessary to immobilize them, thereby enabling repeated or long-term use. In addition, enzyme immobilization usually improves pH and thermal stability by conserving tertiary structures and active sites, which also results in reduced financial costs [7,8]. Many types of enzyme supports exist, including nanoparticles [9,10], nanotubes [11], mesoporous materials [12], sponges [13], and nanofibrous materials [14][15][16].…”