Formulation and characterisation of O/W emulsions stabilised with modified seaweed polysaccharides

In this study, seaweed polysaccharides (alginate and carrageenan) were modified with dodecenylsuccinic anhydride (DSA), and their stabilising properties in oil-in-water (O/W) emulsion system were evaluated. The physicochemical characteristics were determined by droplet size, interfacial tension and ζ-potential and structurally verified by Fourier transform infrared spectroscopy (FTIR). Both CRG-DSA and ALG-DSA applied in O/W emulsion system exhibited smaller droplet sizes over the increasing concentration and were more stable during storage than native ones. The ζ-potential of DSA-modified seaweed polysaccharides has more negative charge compared with their native forms, owing to the additional carboxyl groups from modification reaction. In addition, DSA-modified seaweed polysaccharides decreased the interfacial tension at soybean oil–water interface from 23.1 and 23.9 mN m⁻¹ to 14.2 and 13.6 mN m⁻¹, respectively. The successful modification reaction was confirmed by FTIR analysis. This study demonstrated that DSA-modified seaweed polysaccharides may serve as prospective emulsifiers in food, pharmaceutical and other industrial fields.     

Ultrafiltration recovery of alginate: Membrane fouling mitigation by multivalent metal ions and properties of recycled materials

Recovery of alginate extracted from aerobic granular sludge (AGS) has given rise to a novel research direction. However, these extracted alginate solutions have a water content of nearly 100%. Alternately, ultrafiltration (UF) is generally used for concentration of polymers. Furthermore, the introduction of multivalent metal ions into alginate may provide a promising method for the development of novel nanomaterials. In this study, membrane fouling mitigation by multivalent metal ions, both individually and in combination, and properties of recycled materials were investigated for UF recovery of sodium alginate (SA). The filtration resistance showed a significantly negative correlation with the concentration of metal ions, arranged in the order of Mg²⁺ < Ca²⁺ < Fe³⁺ < Al³⁺ (filtration resistance mitigation), and the moisture content of recycled filter cake showed a marked decrease. For Ca²⁺, Mg²⁺, Fe³⁺, and Ca²⁺+ Fe³⁺, the filtration resistances were almost the same when the total charge concentration was less than 5 mmol⋅L^–1. However, when the total charge concentration was greater than 5 mmol⋅L^–1, membrane fouling mitigation increased significantly in the presence of Ca²⁺ or Fe³⁺ and remained constant for Mg²⁺ with the increase of total charge concentration. The filtration resistance mitigation was arranged in the order of Fe³⁺ > Fe³⁺ + Ca²⁺ > Ca²⁺ > Mg²⁺. Three mechanisms were proposed in the presence of Fe³⁺, such as the decrease of SA concentration, change in pH, and production of hydroxide iron colloids from hydrolysis. The properties of recycled materials (filter cake) were investigated via optical microscope observation, dynamic light scattering, Fourier transform infrared, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. The results provide further insight into UF recoveries of alginate extracted from AGS.     

马拉硫磷微胶囊剂的气相释放行为的研究

本文详细叙述了农药微胶囊剂活性组分气相瞬时释放速率的测定装置和测定方法,并采用所述方法测定以天然高分子材料海藻胶——明胶为囊膜的马拉硫磷微胶囊剂的气相释放行为和壁膜渗透率的研究结果.     

聚阴离子电解质纳米粒子的制备及其表征

探索了一种新的聚阴离子电解质基（海藻酸钠、果胶和羧甲基壳聚糖）的纳米粒子的制备方法.该方法不涉及任何有机溶剂和表面活性剂,并且能够很好的控制聚阴离子电解质基纳米粒子的形貌及粒径.应用扫描电镜（SEM）和透射电镜（TEM）观测了干态纳米粒子的形貌;采用扫描电镜在低真空下以环境扫描模式（ESEM）表征了湿态纳米粒子的形貌,利用纳米粒度仪测定了纳米粒子的粒径及其分布.结果表明,在含有Ca^2＋和CO3^2-的水溶液中,聚阴离子电解质可以自组装成形状规整且分散性好的纳米粒子.     

Rapid temperature/pH response of porous alginate-g-poly(N-isopropylacrylamide) hydrogels

To improve the swelling and deswelling rate, comb-type macroporous hydrogels were prepared. The temperature-sensitive poly(N-isopropylacrylamide) (PNIPAAm) was grafted on the surface or bulk of the pH-responsive alginate. The larger surface area in pores and free chain mobility by comb-type graft copolymer reached its equilibrium swollen state within a minute. The swelling ratio of porous hydrogel in equilibrium state was over fifteen times greater than that of nonporous hydrogels. The increase of surface area by pores caused water molecules to transfer easily in and out of the matrix, resulting in a rapid deswelling. The degree of change in swelling ratio during deswelling might be affected by the phase transition behavior of PNIPAAm attached on only the surface of the pore rather than PNIPAAm grafted into mainchain of alginate. Surface-grafted alginate/PNIPAAm gels had a suitable mechanical strength without collapsing during the repeatable shrinkage and expansion due to swelling and deswelling, whereas bulk-grafted gels easily collapsed.     

Calcium Alginate Microspheres of Bacillus subtilis

Microspheres of Bacillus subtilis were prepared using sodium alginate. Some typical properties of microencapsulated systems, such as microorganism content, particle size, and germination time, were studied. Calcium alginate microspheres were obtained by the emulsification method, dripping into a solution of calcium salt. The conditions of the preparation steps were very soft to produce calcium alginate microspheres containing cells with no apparent changes in general biological properties. The hydrogel matrix provides protection without preventing communication with the surrounding medium.     

Alginate‐based and protein‐based materials for probiotics encapsulation: a review

Owing to their considerable beneficial effects on human health, probiotics have been increasingly incorporated into food products. However, many findings have demonstrated that their survival and stability are very sensitive to processing and host gastrointestinal tract. To solve these problems, encapsulation techniques have been received considerable attention these days. So, in this review paper, methods for probiotics encapsulation, alginate‐based and protein‐based materials for probiotics encapsulation and application of encapsulated probiotics in food industry were discussed.     

Hydrogen production from biopolymers by Caldicellulosiruptor saccharolyticus and stabilization of the system by immobilization

The biopolymers agarose and alginic acid, and hemicellulose-rich pine tree wood shavings, frequently discarded as waste, proved to be utilized as energy sources for hydrogen production by the extreme thermophilic bacterium Caldicellulosiruptor saccharolyticus. The addition of 0.5% (w/v) pine wood shavings to the growth medium yielded a 14-fold increase in hydrogen production over a period of 55 days relative to cultures grown in the same medium without wood shavings (average rate was about 0.45 ml H₂ ml culture⁻¹ day⁻¹). The shavings were also shown to be degraded by C. saccharolyticus in the absence of any other carbohydrate source.     

Functionally graded calcium zirconate molds with alginate-based spray coating for titanium investment casting

Surface quality and dimensional accuracy of titanium components produced by investment casting are limited by the conventional dip-coating procedure of the lost-wax process. This study presents a novel approach with spraying and centrifugation as alternative coating technologies. Aiming at improved surface quality, calcium zirconate slips and coatings based on alginate gelation were developed. Scanning electron microscopy and computed tomography revealed a homogeneous spray coating. The alginate-based spray coating was used for producing functionally graded calcium zirconate shell molds. These molds exhibited a fine-grained microstructure with pores in the lower μm range. Applying an intermediate layer between the fine-grained spray coating and the coarse-grained dip-coating layers as well as the alternating application of dip-coating layers prevented cracking. The characteristic microstructure showed a bridging zone and a homogeneous distribution of coarse grain across the diameter. Ti6Al4V cast parts with no presence of an alpha case layer were obtained.