Improvement of thermal-stability of enzyme immobilized onto mesoporous zirconia

Peer review under responsibility of The Ceramic Society of Japan and the Korean Ceramic Society.

Peer review under responsibility of The Ceramic Society of Japan and the Korean Ceramic Society.

Figures & data

Table 1 Structural properties of mesoporous materials.

Sample name	Pore size^a [nm]	Surface area^b [m^2/g]	Pore volume^a [cm^3/g]	Pore structures^c	Zeta potential^d [mV]	Average particle diameter^d [nm]
MPZ	12.2	70.55	0.2	Disordered	19.5	274.7 ± 146.0
MPS	13.2	723.7	1.8	2D-hexagonal	−13.8	480.6 ± 281.4
IPMPS	14.4	291.8	0.9	Disordered	−30.9	288.5 ± 168.0

a Calculated according to BJH analysis (adsorption branch between 1.7 and 300 nm diameters).

b Specific surface area according to BET.

c Pore structure was obtained from small-angle X-ray diffraction (SAXRD) peaks.

d Calculated value was obtained from zeta potential and particle size distribution measurements.

Fig. 1 Nitrogen adsorption–desorption isotherms and BJH analysis [inset] for MPZ [circular], MPS [square] and IPMPS [triangle].

Fig. 2 FE-SEM (a–c) and TEM (A–C) images of the synthesized mesoporous materials. (A, a): MPS, (B, b): IPMPS, (C, c): MPZ.

Fig. 3 EDX profiles and EDX mapping images of MPZ. The zirconia and oxygen mapping images all agree well the STEM image.

Fig. 4 (a) FDH adsorption on different supports. Immobilized method was shown in Section 2.6. (b) Relative activities of FDH immobilized on each mesoporous materials.

Table 2 Apparent K_m, K_cat, and K_cat/K_m values at three mesoporous materials, calculated using the Michaelis–Menten equation.

Sample name	Km [mM]	Kcat [min^−1]	Kcat/Km
Native	0.249	12.1	48.6
MPZ	0.117	5.23	44.7
MPS	0.509	3.62	7.11
IPMPS	0.285	6.18	21.7

Fig. 5 (a) FT-IR spectra of the native and immobilized FDHs on various MPS materials. The native FDH is denoted by the solid line. The FDHs on MPZ, MPS and IPMPS are denoted by the dashed, dotted and dot–dot dashed lines, respectively. (b) Circular dichroism spectra of the native and immobilized FDHs on various absorbents. Native FDH is denoted by solid line. FDHs on MPZ, MPS and IPMPS are denoted by dashed, dotted and dot–dot dashed lines, respectively.

Fig. 6 (a) Thermal stability as a function of time for the native [circle] and immobilized FDHs on MPZ [white circle], MPS [triangle] and IPMPS [square] at 40 °C in 50 mM–pH 7.0–phosphate buffer. Initial activities are considered as 100%. (b) Differential scanning calorimetry curves for the Native [solid line] and immobilized, FDH on MPZ [dashed line], MPS [dotted line] and MPZ [dot–dot dashed line].

Fig. 7 Analysis of changes in the secondary structure of native and immobilized FDHs on various supports after thermal process. FT-IR: (a)–(c), CD spectra: (A)–(D).