Comprehensive utilization of activated sludge for the preparation of hydrolytic enzymes, polyhydroxyalkanoates, and water-retaining organic fertilizer.

The urban wastewater treatment industry produces a large amount of excess activated sludge which is mainly composed of microbial biomass and costly to be disposed. In this research, a comprehensive utilization of activated sludge was developed by sequentially extracting hydrolytic enzymes and polyhydroxyalkanoates (PHAs), and the residue was used to prepare water-retaining organic fertilizer. The sludge was extracted with fourfold H2O-containing 1% Triton X-100 with the yield of 66.7% protease activity. The enzyme solution was precipitated in 80% acetone and vacuum dried at 40°C at the dried enzyme yield of 2.4 g/kg wet sludge. The enzyme product contains collagenase, lipase, amylase, and cellulase activities, which are good compound enzymes to feed. The PHAs were extracted with 30% sodium hypoclorite:chloroform (1:3). The PHA solution was decolored and dried, and pure white PHAs were obtained at the yield of 70.1 g/kg wet sludge. The residue was used to prepare water-retaining organic fertilizer at the optimal condition. The fertilizer absorbs 131.3-fold distilled water and had good performance in water retention and can effectively slow down the loss of soil moisture when added into soil. This work provides a simple and practical approach for comprehensive utilizing activated sludge with significant economic benefits.

Expression of nattokinase in Escherichia coli and renaturation of its inclusion body.

Nattokinase is an important fibrinolytic enzyme with therapeutic applications for cardiovascular diseases. The full-length and mature nattokinase genes were cloned from Bacillus subtilis var. natto and expressed in pQE30 vector in Escherichia coli. The full-length gene expressed low nattokinase activity in the intracellular soluble and the medium fractions. The mature gene expressed low soluble nattokinase activity and large amount insoluble protein in inclusion bodies without enzyme activity. Large amount of refolding solutions (RSs) at different pH values were screening and RS-10 and RS-11 at pH 9 were selected to refold nattokinase inclusion bodies. The recombinant cells were lysed with 0.1mg/mL lysozyme and ultrasonic treatment. After centrifugation, the pellete was washed twice with 20mM Tris-HCl buffer (pH 7.5) containing 1% Triton X-100 to purify the inclusion bodies. The inclusion bodies were dissolved in water at pH 12.0 and refolded with RS-10. The refolded proteins showed 42.8IU/mg and 79.3IU/mg fibrinolytic activity by the traditional dilution method (20-fold dilution into RS-10) and the directly mixing the protein solution with equal volume RS-10, respectively, compared to the 52.0IU/mg of total water-soluble proteins from B. subtilis var. natto. This work demonstrated that the inclusion body of recombinant nattokinase expressed in E. coli could be simply refolded to the natural enzyme activity level by directly mixing the protein solution with equal volume refolding solution.

[The ultrastructural study of bonding interface between two adhesive systems and three types of dental hard tissue].

PURPOSE: To compare of the morphological ultrastructure of the 7th generation self-etching adhesive Adper Easy One and two-step total etch adhesive Adper Singlebond 2 after being bonded with the composite resin. METHODS: Buccal and lingual box-like holes were made in 20 isolated human molars (5mm in diameter, 3mm in depth), and cuted to pieces from surface of middle part of root (5mm in length, 3mm in width). They were equally divided into 2 groups with 10 root slices and 10 crowns each. The cavities of crown and root pieces were respectively bonded with adhesives of Adper Singlebond 2 and Adper Easy One, and were vertically cuted open from the midline after filling with composite resin to get 20 specimens in each group. Ten specimens of root and crown were randomly selected from each group for 5000 times of thermocycling, and the remaining specimens were soaked in distilled water at room temperature for 1 month. Then all the specimens were polished with sand paper, fixed dehydrated, vacuum dried and sprayed, and the bonding interfaces of the filling edge of profile were scanned by scanning electron microscope(SEM). RESULTS: SEM photos showed that in the group of total etching Adper Singlebond 2 bonding placed at room temperature, the enamel, cementum and the resin bonded closely with the adhesive after thermocycling. In the group of self etching Adper Easy One bonding placed at room temperature, the adhesive bonded to the enamel, small cracks were occasionally seen, and resin penetration blend within the resin in dentinal tubules, and enamel bonded well to the cementum. The specimens after thermocycling bonded enamel loosely with distinct cracks,while the dentinal tubules and resin penetration integrated and cementum bonded well to the dentin. CONCLUSIONS: Ultra-micro structure observation by SEM shows that Adper Singlebond 2 total etch adhesive has better bonding to enamel than the self-etching adhesive Adper Easy One, but the bonding to dentin and cementum has no significant difference.

Comparison study of harmonic imaging (HI) and fundamental imaging (FI) in fetal echocardiography.

OBJECTIVES: To directly compare the quality of harmonic imaging (HI) and fundamental imaging (FI) in fetal echocardiography and to determine any differences in image quality between the two modalities. METHODS: Fetal echocardiograms were performed with the use of FI and HI in 58 fetuses, image quality and visualization of left and right atria, left and right ventricles, mitral and tricuspid valves, aortic and pulmonary valves, left and right ventricular outflow tracts were evaluated and compared between FI and HI. RESULTS: Mean HI scores were higher than mean FI scores (2.73 +/- 0.43 vs 2.16 +/- 0.69, P < 0.001) for all the cardiovascular structures evaluated. Compared with FI, HI improved the image quality and visualization of fetal cardiac structures in subjects with both good (2.73 +/- 0.43 vs 2.88 +/- 0.32, P < 0.001) and suboptimal (1. 65 +/- 0.41 vs 2.58 +/- 0.47, P < 0.001) echocardiographic windows. The interobserver correlation coefficient for the grading scores was 0.74 (P < 0.001). CONCLUSIONS: harmonic imaging enhances and improves the image quality of fetal echocardiography; and has important potential role in cardiac imaging in the fetus.