Highly Efficient and Stable Novel NanoBiohybrid Catalyst to Avert 3,4-Dihydroxybenzoic Acid Pollutant in Water

Abstract

The present study reported for the first time covalent immobilization of protocatechuate 3,4-dioxygenase (3,4-POD) onto functionalized multi-walled carbon nanotubes (F-MWCNT) for degrading the toxic 3,4-dihydroxybenzoic acid (3,4-DHBA) pollutant in water. The F-MWCNTs had a maximum 3,4-POD loading of 1060 μg/mg. Immobilized 3,4 POD had 44% of relative structural changes to its free configurations. Nevertheless, >90% of relative activity and about 50% of catalytic efficiency were retained to the free enzyme. Immobilized 3,4-POD demonstrated higher alkaline stability and thermostability than the free 3,4-POD. The free and immobilized 3,4-POD lost 82% and 66% of relative activities, respectively after 180 min of incubations at 90 °C. Excellent shelf-life was observed for the immobilized 3,4-POD with residual activity of 56% compared with 41% and 39% of the free 3,4-POD at 4 °C and 25 °C over 30 days storage. Immobilized 3,4-POD showed >60% of catalytic activity retention even after ten-cycle uses, defraying the expenses of free 3,4-POD productions for long term uses. Finally, the immobilized 3,4-POD removed 71% of 3,4-DHBA from water in <4 h, paving its future application for water purification with reduced costs and time.

Can We Optimize Arc Discharge and Laser Ablation for Well-Controlled Carbon Nanotube Synthesis?

“…Since the material first defined by Iijima [5] in 1991, CNTs have demonstrated magnificent shoot in many disciplines including polymer and composites [6], conductive cable fibers and thermoplastics [7], hydrogen storage media [8], biomedical sciences [9], field emission devices [10], environmental remediation [11–13], electrochemistry and nanosensors [14, 15], nanoelectrode arrays or microarrays [16, 17], optoelectronic devices [18], catalyst supports [19, 20], and numerous others [21, 22]. Recently, National Aeronautics and Space Administration (NASA) scientists and others have explored the gold rush possibility for CNT applications in aerospace research, especially for enhanced radar adsorption.…”

Covalent immobilization of phytase on the multi-walled carbon nanotubes via diimide-activated amidation: structural and stability study

“…As shown in Figure 3, the peaks at 3438, 1641 and 1737 nm confirmed the presence of (-OH), (-C¼O) and (-COOH), respectively [24], indicating complete oxidation of MWNTs. The stretching vibration of (-COOH) shown in Figure 3 indicates the attachment of the enzyme molecules on the nanotubes [26]. As presented in Figure 3(a), unique peaks observed at 3346 and 3257 nm belonging to (N-H) bonds in phytase molecule confirmed the presence of phytase on the surface of functionalized MWNTs [34].…”

“…Circular dichroism (CD) spectroscopy was performed to determine the structural changes and monitoring the secondary structure of free and immobilized phytase [26]. The UV CD spectra (190-260 nm) were recorded on a CD spectrometer model-215 Aviv (New Jersey, USA) with a bandwidth of 1 nm.…”

“…To obtain a higher phytase loading efficiency and activity, different concentrations of free phytase (57-1800 mg/ml) vs. 2 mg functionalized MWNT were taken into account and then the protein content for each experiment was measured using the Bradford assay method to obtain loading efficiency (%) (Equation (1)) [21]. For determining the of immobilization yield (%), specific activities of both free and immobilized enzymes were calculated for each initial phytase concentration (57-1800 mg/ml) (Equation 2 Figure 1(a) shows that increasing initial phytase concentration from 110 to 187 mg per mg of functionalized MWNTs led to a reduction in loading efficiency from 98.34% to 20.83%, the amount of enzyme immobilized onto functionalized MWNTs increased from 11% to 18.75% though [26]. Therefore, the optimum initial phytase concentration was 110 mg per mg of functionalized MWNTs leading to the highest loading efficiency recorded (Table 1, Figure 1).…”

“…For instance, Cang-Rong and Pastorin reported that covalent immobilization of amyloglucosidase on MWNTs retained 38% of the initial activity [30]. While Das et al claimed that after the immobilization of protocatechuate 3,4-dioxygenase (3,4-POD) on MWNTs, the retained activity ranged between 66% and 95% under different experimental circumstances [26]. These findings reveal the critical role of the enzyme to nanosupport ratio in achieving the highest immobilization yield possible.…”