Dextran is a bacterial polysaccharide which can be produced from sucrose and usually used for clinical treatment as one kind of practical polysaceharide drags. The molecular weight distribution of dextran is an important index for its application. However, it is hardly to control strictly by the traditional separating method with ethanol. Taking separation and purification of medicinal dextran as the object of this study, a new separation technology, coupling electro-ultra-filtration with solvadng-out-crystagization (EUF-SOC) was developed and applied successfully, It was found that the permeate flux of optimized EUF-SOC technology is several times of normal ultra-filtration (UF) or enhanced ultrafiltration with an electric field (EUF), and its quality is higher than that of traditional process. The selective crystallization of dextran can be realized and homogeneous dextran crystals can be got in the process of membrane filtration by using EUF-SOC technology. The results showed that the mass transfer coefficient (k) of EUF-SOC process is about 4 times of UF and 2 times of EUF.

Zirconia nanopowders were prepared in the ultrasonic field by the sol-gel method and the sonochemical effect on the structure of zirconium hydroxide and the zirconia nanopowder properties were systematically investigated in this work. Ultrasound was introduced into the different stages of the synthesis of zirconia nanopowders in sol-gel reaction system, and zirconium hydroxides and the zirconia nanopowders with different properties were obtained. The results indicated that ultrasonic cavitation could not only disaggregate the agglomerates of zirconia colloidal particles but also reduce the amount of coordinated H2O, free H2O and free hydroxyl groups of the zirconium hydroxide colloidal particles, thus effectively preventing the formation of hard agglomerates in zirconia powders. Moreover, the effects of different ultrasonic output powers and treatment cycles on the structure and properties of ZrO2 nanopowders were studied by TEM, XRD and SAXS. Zirconia nanopowders with an extremely small crystallite size (10.3 nm) and a narrow size distribution were yielded with 520 W ultrasound for 6 treatment cycles on the formation period and 600 W ultrasound for 2 treatment cycles on the washing period. It is concluded that the ultrasonic field is a potential method for nanopowder preparation.

Abstract: The objective of the study was to evaluate the effect of a novel biodegradable membrane on the prevention of postoperative adhesion formation. The membrane was prepared by blending 50% PLA (polylactic acid) with 50% PTMC (polytrimethylene carbonate). The prepared blends polymer membrane was more flexible than pure PLA membrane, as measured by glass-transition temperature and tensile study. Cytotoxicity study revealed that PLA/PTMC blends membrane showed good biocompatibility. The membrane elicited slight tissue reaction based on the results of histological study. Thirty adult Japanese rabbits were used for the intestine adhesion model. The treatment group had PLA/PTMC membrane, the control group had chitosan, and the blank control group was not operated. The animals were housed for two weeks and sacrificed to investigate adhesion of intestine. Compared with the blank control group, the treatment group and the control group lowered the extent of adhesions (p < 0.01), but the treatment group was better than the control group (p < 0.05). The in-vivo studies confirmed that PLA/PTMC blends membrane could prevent postoperative adhesions.

The influence of covalent cross-linking by microbial transglutaminase (MTGase) on the sequential in vitro pepsin and trypsin digestion process and the digestibility of soy protein isolate (SPI), was investigated by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and nitrogen release analyses. Various subunits of b-conglycinin and acidic subunits of glycinin were cross-linked by MTGase to form high molecular weight (MW) biopolymers, while basic subunits of glycinin were unaffected. SDS-PAGE analysis indicated that the cross-linking mainly affected in vitro pepsin digestion pattern of various subunits of b-conglycinin, while the trypsin digestion pattern of native SPI was nearly unaffected. Nitrogen release analysis showed that the in vitro pepsin or/and trypsin digestibility of native SPI (at the end of pepsin or trypsin ingestion) was significantly decreased (P＞0.01) by the MTGase treatment (for more than 2 h). The cross-linking by MTGase also significantly decreased the in vitro digestibility of preheated SPI. These results suggest that the cross-linking by means of transglutaminase may negatively affect the nutritional properties of food proteins.

This article reviews recent advances in polymer blends and composites from renewable resources, and introduces a number of potential applications for this material class. In order to overcome disadvantages such as poor mechanical properties of polymers from renewable resources, or to offset the high price of synthetic biodegradable polymers, various blends and composites have been developed over the last decade. The progress of blends from three kinds of polymers from renewable resources-(1) natural polymers, such as starch, protein and cellulose; (2) synthetic polymers from natural monomers, such as polylactic acid; and (3) polymers from microbial fermentation, such as polyhydroxybutyrate-are described with an emphasis on potential applications. The hydrophilic character of natural polymers has contributed to the successful development of environmentally friendly composites, as most natural fibers and nanoclays are also hydrophilic in nature. Compatibilizers and the technology of reactive extrusion are used to improve the interfacial adhesion between natural and synthetic polymers.