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

Figures & data

Figure 1. Loading efficiency of immobilized phytase on F-MWNT (a) and immobilization activity yield (b).

Table 1. Amount of initial and immobilized phytase (µg) on 1 mg of MWNTs and loading efficiency.

Run (immobilizationprocess)	Immobilized (µg/mg)	Free (µg/mg)	Efficiency (%)
1	28.5	28.75	99.13
2	58	59.25	97.89
3	110.05	111.9	98.35
4	108.1	125.65	86.03
5	109	250	43.6
6	110.7	457.8	24.18
7	148.7	600	24.78
8	187.5	900	20.83

Figure 2. Scanning electron microscopy of functionalized MWNTs (a) and phytase-MWNTs composites (b).

Figure 3. FTIR spectra of functionalized MWNTs (b) and immobilized phytase (a).

Figure 4. CD spectroscopy of free and immobilized enzyme. MES buffer (a), functionalized MWNTs (b), immobilized (c) and free phytase (d). MES buffer and enzyme-free functionalized MWNTs were used as controls to eliminate noises.

Figure 5. pH (a) and temperature (b) profile of free and immobilized phytase.

Figure 6. Effect of NaCl concentrations on enzymatic activity of free and immobilized enzyme shown at two different scales.

Figure 7. Temperature stability of free and immobilized phytase at 90 (a), 80 (b), 70 (c) and 60 °C (d).