Shubao Shen

Enhancement of microwave-assisted covalent immobilization of penicillin acylase using macromolecular crowding and glycine quenching.

In order to create macromolecular crowding resembling cells in mesopores and improve the covalent immobilization of penicillin acylase (PA), macromolecular reagents were covalently assembled on the walls of mesocellular silica foams (MCFs) and paralleled enzyme molecules under microwave irradiation at low temperatures. The effects of kind and content of macromolecules on immobilization and the characteristics of the immobilized enzyme were investigated carefully. The maximum specific activities of PA assembled with Dex 10 (Dextran, Mw 10000) (85.3 U/mg) and BSA (Bovine Serum Albumin) (112.7 U/mg) in MCFs under microwave irradiation were 1.73 and 1.31 times, respectively, that of PA solely immobilized by the conventional method. The optimum reaction temperature rose from 45-55 degrees C. Moreover, amino acids were used to quench excess activated groups in order to improve the thermostability of the immobilized enzyme. PA coassembled with Dex 10 in mesopores retained 88% of its initial catalytic activity after heating at 50 degrees C for 6 h, as a result of glycine quenching the excess activated groups. This biomolecule enhanced the thermostability of the enzyme preparation by 2-fold. A crowding environment resembling cells made from macromolecular reagents would be suitable for stabilizing the structure of PA and improving its catalytic activity. Glycine, a small biocompatible molecule, quenched the excess activated groups and modified the surface chemical properties of the mesoporous support, which would further favor the stability of PA at higher temperatures. Combining macromolecular crowding with glycine quenching was one of the efficient strategies adopted to improve microwave-assisted covalent PA immobilization.

Ag-induced Efficient Immobilization of Papain on Silica Spheres

Abstract Complexation and interaction between silver and amino group were applied to induce an efficient immobilization of papain on silica spheres. The silver nanoparticles were deposited on the silica spheres before papain was coupled to the silica spheres. The silica spheres with silver nanoparticles were characterized by high resolution transmission electron microscopy (HR-TEM), Fournier transform infrared spectroscopy (FT-IR), and UV-Vis scanning spectrometer. FT-IR spectrum was also used to characterize the immobilized and free papain. Effect of some factors on the activities of the immobilized papain was investigated. It was observed that the coupled yield and relative activity of the papain on Ag/SiO 2 were 1.17 and 1.86 times of those on the bare SiO 2 , respectively. At an optimum concentration of silver, the observed activity of the immobilized papain was 2.1 times of that on the bare silica. In addition, the maximum specific activity of papain immobilized on Ag/SiO 2 was 819.9 U·mg −1 , which is slightly lower than that of the free papain, 906.2 U·mg −1 . Stability of the immobilized papain was also examined. The results indicate that the silver nanoparticles successfully induce a fine immobilization of papain.

High yield hydrogen production in a single-chamber membrane-less microbial electrolysis cell.

The single-chamber membrane-less MEC exerted much better hydrogen production performance while given higher applied voltages than it did at lower. High applied voltages that could shorten the reaction time and the exposure of anode to air for at least 30 min between cycles can significantly suppress methanogen and increase hydrogen production. At an applied voltage of 1.0 V, a hydrogen production rate of 1.02 m(3)/m(3)/day with a current density of 5.7 A/m(2) was achieved. Cathodic hydrogen recovery and coulombic efficiency were 63.4% and 69.3% respectively. The hydrogen concentration of mixture gas produced of 98.4% was obtained at 1.0 V, which was the best result of reports. The reasons that such a high hydrogen concentration can be achieved were probably the high electrochemical activity and hydrogen production capability of the active microorganisms. Increase in substrate concentrations could not improve MECs performance, but increased the reaction times. Further, reactor configuration and operation factors optimisation should be considered to increase current density, hydrogen production rate and hydrogen recovery.

Covalent Assembly of Penicillin Acylase in Mesoporous Silica Based on Macromolecular Crowding Theory

Abstract To improve the covalent immobilization of penicillin acylase (PA), macromolecular crowding theory was applied to its immobilization. Influence of mass ratio of enzyme to the silica, as well as, activation time with glutaraldehyde on the activity of assembled PA, was studied. In the mesopores, the effect of β-cyclodextrin (β-CD) on the immobilization of the enzyme was also investigated. It was remarkable that the coupled yield and relative activity reached 99.5% and 92.3%, respectively, when penicillin acylase assembled covalently in the mesopores. The results here indicate that mimicked macromolecule crowding could significantly ameliorate the performance of covalently immobilized PA.

Study on catalytic combustion of benzene over cerium based catalyst supported on cordierite

Abstract A series of MnCeOx catalysts supported on cordierite honeycomb (Cord) were prepared by a combustion synthesis method using Mn(NO3)2, Ce(NO3)2·6H2O and citric acid. The effect of the molar ratio of Mn/Ce, calcination time, the amount of citric acid and the effect of water vapor on the catalytic properties for the complete oxidation of benzene were investigated. These catalysts were characterized by X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), O2 temperature programmed desorption (O2-TPD) and scanning electron microscopy (SEM) techniques. The results indicated that the MnCeOx/Cord catalyst with Mn/Ce molar ratio of 1:1, calcining for 7 h and Mn+/(citric acid) molar ratio of 6 exhibited the highest catalytic activity. When the concentration of benzene was 1500 ppm and the gaseous hourly space velocity was 20000 h−1, the conversion of toluene was 99.1% at the reaction temperature of 300 –C.

Preparation of Fe-Cu catalysts and treatment of a wastewater mixture by microwave-assisted UV catalytic oxidation processes.

Microwave‐assisted UV catalytic oxidation (MW/UV) is a potential method to treat organic pollutants that have non‐biological degradability and high toxicity. To achieve high treatment efficiency, it is crucial to prepare heterogeneous photocatalysts with a high activity. Iron–copper catalysts were prepared by four different methods. Synthetic wastewater containing aniline and nitrophenol (TOC = 1000 mg/L) was treated. The key parameters including the proportion of Fe2O3 and CuO and the total content of the active components are discussed. The optimum catalyst dosage and the whole catalytic oxidation process were investigated, and different catalytic oxidation systems were also compared. The catalyst prepared by impregnation was best: the highest TOC removal efficiency reached 78%. The optimum proportion of Fe2O3 and CuO and the content of the total active composition were 4:1 and 30%, respectively. The catalyst preparation method had a greater influence on the MW/UV system than on the microwave (MW) system, and the synergistic effect between MW and UV was verified. The MW/UV system was more susceptible to catalyst dosage than was the MW system, and the optimum catalyst dosage was 5 g/L. The catalyst and H2O2 had a synergistic effect. The presence of a possible non‐thermal microwave effect could be expected.

Promotional effects of copper doping on Ti-Ce-Ox for selective catalytic reduction of NO by NH3 at low temperature

Abstract A series of copper-doped Ti-Ce-O x complex oxide catalysts were synthesized by sol-gel method and evaluated for selective catalytic reduction of NO by NH 3 at low temperature. The promotional effect of copper doping on their structure, acidity and catalytic activity were investigated by means of Brumauer-Emmett-Teller (BET), temperature-programmed reduction (H 2 -TPR), X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature programmed desorption (NH 3 -TPD) and pyridine adsorption infrared spectrum (Py-IR) technologies. Results showed that the copper additives could improve the low temperature catalytic performance for selective catalytic reduction of Ti-Ce-O x catalyst and the NO conversion efficiency of Ti-Cu-Ce-O x catalyst reached above 90% at 150–250 °C (Ti/Cu=4). The introduction of copper could enhance the redox property of the Ti-Ce-O x complex oxide catalyst, refine the particle size caused by lattice distortion and oxygen vacancy defect and enhance the acid amount of the Lewis acid site. Moreover, Ti-Cu-Ce-O x complex oxide catalyst also had good anti-sulfur ability and anti-water influence, when injecting 300 ppm SO 2 and 10 vol.%H 2 O, the NO conversion efficiency of Ti-Cu-Ce-O x catalyst reached 80%.

Anaerobic degradation of purified terephthalic acid wastewater using a novel, rapid mass-transfer circulating fluidized bed

The anaerobic treatability of purified terephthalic acid (PTA) wastewater in a novel, rapid mass-transfer fluidized bed reactor using brick particles as porous carrier materials was investigated. The reactor operation was stable after a short 34 day start-up period, with chemical oxygen demand (COD) removal efficiency between 65 and 75%, terephthalate (TA) removal efficiency between 60% and 70%, and system organic loading rate (OLR) increasing from 7.37 to 18.52 kg COD/m(3) d. The results demonstrate that the reactor is very efficient, and requires a low hydraulic retention time (HRT) of 8 h to remove both TA and COD from the high-concentration PTA wastewater. The system also has high resistance capacity to varied OLR.

Promotional effect of phosphorylation on CeSn0.8W0.6Ox/TiAl0.2Si0.1Oy for NH3-SCR of NO from marine diesel exhaust

Abstract A series of phosphorylation and blank CeSn 0.8 W 0.6 O x /TiAl 0.2 Si 0.1 O y catalysts prepared by extrusion molding were tested for NH 3 -SCR of NO, and were characterized by techniques of X-ray diffraction (XRD), Brumauer-Emmett-Teller (N 2 -BET), environmental scanning electron microscope (ESEM), temperature programmed reduction (H 2 -TPR) and temperature programmed desorption (NH 3 -TPD). Effects of phosphorylation on catalytic activity and sulfur-resisting performance of the CeSn 0.8 W 0.6 O x /TiAl 0.2 Si 0.1 O y for NH 3 -SCR of NO were mainly studied. Results showed that the phosphorylation improved the catalytic activity and sulfur-resisting performance in an active temperature window of 300–440 °C, and the phosphorylation catalyst with 0.4 wt.% H 3 PO 4 exhibited the best catalytic performance and the strongest sulfur-resisting performance. Analysis showed that the phosphorylation increased specific surface area, enhanced the surface acidity and improved redox properties.

A novel chemical/biological combined technique for N, N-dimethylformamide wastewater treatment

ABSTRACT N, N-Dimethylformamide (DMF) is a widely used organic solvent whose wastewater is difficult to biodegrade directly. In this paper, a novel chemical/biological combined technique consisting of alkaline hydrolysis stripping, activated sludge and a bio-trickling filter (BTF) was developed for DMF wastewater treatment. The main pollutant, DMF, was decomposed to dimethylamine and formate under alkaline conditions, and the dimethylamine was stripped out by the BTF. The pretreated wastewater was then degraded in an activated sludge process. The operation performances of alkaline hydrolysis, activated sludge and BTF processes were investigated separately. At the optimal conditions of an alkali dosage of 40 g/L, an air/liquid ratio of 3000:1 and 5 h in the air-stripping process, the removal of total organic carbon and DMF was found to be 58% and 96%, respectively. A chemical oxygen demand removal efficiency of 80–90% was obtained in the activated sludge process. The performance of BTF was excellent with a dimethylamine removal efficiency close to 90% even at a high loading of 16 g/d.