Xiaoxia Lei

Immobilization of laccase on magnetic bimodal mesoporous carbon and the application in the removal of phenolic compounds.

A novel magnetically separable laccase immobilized system was constructed by adsorbing laccase into bimodal carbon-based mesoporous magnetic composites (CMMC). A large adsorption capacity (491.7 mg g(-1)), excellent activity recovery (91.0%) and broader pH and temperature profiles than free laccase have been exhibited by the immobilized laccase. Thermal stability was enhanced to a great extent and operational stability was increased to a certain extent. The shift of kinetic parameters indicated affinity change between enzyme and substrate. Application of the immobilized system in phenol and p-chlorophenol removal was investigated in a batch system. Adsorption effects of the support were responsible for the quick removal rate in the first hour, and up to 78% and 84% of phenol and p-chlorophenol were removed in the end of the reaction, respectively, indicating that the magnetic bimodal mesoporous carbon is a promising carrier for both immobilization of laccase and further application in phenol removal.

Cr(VI) reduction by Pseudomonas aeruginosa immobilized in a polyvinyl alcohol/sodium alginate matrix containing multi-walled carbon nanotubes.

Pseudomonas aeruginosa (P. aeruginosa) was immobilized with polyvinyl alcohol (PVA), sodium alginate and multiwalled carbon nanotubes (MCNTs). After immobilization, the beads were subjected to freeze-thawing to enhance mechanical strength. When exposed to 80 mg/L Cr(VI), the immobilized bacteria were able to reduce 50% of them in 84 h, however the free cells were deactivated at this concentration. The beads were used to reduce 50 mg/L Cr(VI) for nine times, with the reduction efficiency above 90% in the first five times and 65% in the end.

Removal and recovery of Zn2+ and Pb2+ by imine-functionalized magnetic nanoparticles with tunable selectivity.

This research investigated the adsorption of zinc and lead from binary metal solution with tunable selectivity. A nano adsorbent was prepared by introducing imine groups onto the surface of stability enhanced magnetic nanoparticles and then characterized by TEM and FTIR. Binary metal components adsorption was carried out in different concentration of metal and EDTA solution. Due to the interaction between metals and adsorbent in the presence of EDTA, the selective adsorption of zinc and lead could be achieved with 100% selectivity. To only remove zinc from binary metals, the solution condition was [EDTA]/[M(2+)] = 0.7 with pH of 6, and its saturated adsorption capacity was 1.25 mmol/g. For selective adsorption of lead, an equilibrium adsorption capacity of 0.81 mmol/g was obtained under the condition of [EDTA]/[M(2+)] = 0.7 and pH of 2. The exhausted adsorbent could be regenerated by simple acid or alkali wash, and high purity lead and zinc salt solutions were recovered and concentrated.

Optical detection of NADH based on biocatalytic growth of Au-Ag core-shell nanoparticles.

We have developed an optical assay for NADH (Dihydronicotinamide adenine dinucleotide) based on the catalytic growth of gold-silver core-shell nanoparticles (Au-Ag-CSNPs). The nanoparticles were immobilized on pretreated glass slide and are shown to catalyze the NADH-mediated reduction of Ag(I) ions in the presence of 1,4-benzoquinone and cetyltrimethyl ammonium ion. This leads to the formation of Au-Ag-CSNPs on the glass. The absorption peak of the Au-Ag-CSNPs at 415 nm increases with the concentration of NADH in the solution used, and this can be measured by UV-vis photometry. High-resolution scanning electron microscopy analysis of the morphology of the surface of the Au-Ag-CSNPs before and after the catalytic reaction revealed a growth of their diameter. Under optimal conditions, NADH can be determined in the concentration range from 0.2 to 3.2mM, and the detection limit is 15.6 μM. The sensor has good precision and good storage stability, simple in operation, and can be fabricated at low costs, which made it suitable for the determination of NADH in complex biological systems and in related degradation processes of contaminants.

Magnetic separation and detection of a cellulase gene using core-shell nanoparticle probes towards a Q-PCR assay

A magnetic separation and detection method for a target sequence of a gene encoding cellulase using biocompatible core–shell nanoparticle probes was developed. An aminated capture probe was conjugated with biocompatible Fe3O4–SiO2–Au core–shell nanoparticles. The target probe and signal probe were hybridized with the capture probe on the surface of the inorganic DNA carrier, which resulted in core–shell nanoparticle probes. In the presence of an external magnetic field, it is convenient and time-saving to realize the detection of the cellulase gene in Trichoderma reesei (T. reesei) by liquid fermentation and subsequent magnetic separation. Quantitative PCR (Q-PCR) was performed to give absolute quantification of the concentration of the target nucleic acid, and the Q-PCR result was compared to that of the electrochemical method. The optimized experimental conditions were studied to maximize the hybridization efficiency and detection sensitivity. The amperometric current response was linearly related to the common logarithm of the target nucleic acid concentration in the range of 1.0 × 10−13 to 1.0 × 10−9 M, with a detection limit of 1.2 × 10−14 M.