Page 133 - IJB-9-3

International Journal of Bioprinting Programmable formaldehyde dehydrogenase for biodegradation formaldehyde

Figure 4. Reuse of immobilized PFDH of various particle sizes (1.5 mm, 2.5 mm, and 3.5 mm).

2.5 mm showed better performance in terms of recycling CA microspheres, and the swelling rate of 1.5 mm PFDH/
times and enzyme activities. In the process of reaction, the CA microspheres were the largest. These data explained the
increase of relative enzyme activity may be caused by the trends in the relative activity of the different print sizes of
expansion behavior of immobilized microspheres during PFDH/CA microspheres in the recycle experiments. About
the recycling of SA, which may expand the space for the 1.5 mm PFDH/CA microspheres have a high swelling
enzyme reaction and also provide a water environment for rate so it can first achieve the maximum relative activity
enzyme, accelerating the transfer of substances. As the pH with a faster rate of substrate transfer and diffusion, but
increases, the -COOH group of CA continues to dissociate, at the same time, the high swelling rate also leads to an
the hydrophilicity of CA increases, and the molecular unstable microsphere structure that is fragile after repeated
chain lengthens, which provides favorable conditions manipulations. Several advantages of 2.5 mm PFDH/
for the enzyme reaction . This process expands the CA microspheres, which have a moderate swelling rate,
[44]
reaction space of the enzyme, and improves the transfer are high reuse frequency, high relative activity and good
and diffusion of the substrate. In the application process, material stability compared to PFDH/CA microspheres
enzyme activity was gradually improved, which is very of other sizes. The swelling rate of 3.5 mm PFDH /CA
conducive to degradation of formaldehyde. It is well known microspheres were the lowest, and the mass transfer and
that indoor formaldehyde has toxic effects on the human diffusion were slower. Based on the experiment of swelling
body, and the immobilized PFDH/CA microspheres have and recycling ability, the 2.5 mm PFDH /CA microspheres
high reusability and stability, which are helpful to efficiently were more suitable for subsequent experiments.
degrade formaldehyde and beneficial for human health.
3.6. Catalysis characterization
3.5. Swelling experiment The 3D-printed PFDH/CA microspheres were
Swelling is the expansion of the volume of a polymer in a characterized and analyzed. Scanning electron microscopy
solvent. The swelling rates of PFDH/CA microspheres were (SEM) images of the PFDH/CA microspheres are shown in
studied by different drying methods. The swelling rates Figure 6A–C, showing the distribution of CA and PFDHs.
of immobilized PFDH/CA microspheres with different The morphology of free PFDH is shown in Figure 6A. The
sizes were studied in 1 mL PBS at 4°C under drying or surface structure and the internal structure of PFDH/CA
freeze-drying conditions. Based on Figure 5, the swelling microsphere are shown in Figure 6B and 6C, respectively.
rates of samples treated by the different drying methods Enzymes may be immobilized in the material or attached
were similar, but the swelling rates of samples treated by to the surface of the material. The FI-TR diagram shows
the freeze-drying method were higher. Regardless of the that between 1500–1700 cm and 3000–3500 cm are
−1
−1
drying conditions, the swelling rate of 3.5 mm PFDH/CA the hydroxyl peaks, as shown in Figure 6D . When the
[45]
microspheres were the smallest, followed by 2.5 mm PFDH/ material was combined with the enzyme, there was no
Volume 9 Issue 3 (2023) 125 https://doi.org/10.18063/ijb.695