Structural and Rheological Characteristics of Alginate from Sargassum cristaefolium Extracted by Twin Screw Extruder

This study aimed to investigate the effects of process extrusion on the characteristics of Sargassum cristaefolium sodium alginate (SCSA) extracted using twin-screw extruder. Box-Behnken Design (BBD) from response surface methodology (RSM) was established to understand the effects of temperature, screw speed, and pH on the multiple-responses of alginate characteristics including intrinsic viscosity, yield, and molecular weight. The results revealed that temperature, screw speed, and pH significantly affected (P < .05) all responses. The optimum extraction condition was found at temperature of 58.18°C, screw speed of 77.99 rpm, and pH 10.11. At this condition, the response of residence time distribution was 7.07 ± 0.029 min, yield of 34.01 ± 0.12%, intrinsic viscosity of 460.13 ± 14.75 mL/g, and molecular weight of 217.94 ± 7.14 × 10³ g/mol. This alginate had mannuronic acid to guluronic acid (M/G) ratio of 0.28, and the L-guluronic acid block was 0.78, which was higher than the D-mannuronic acid block. Rheological characterization of SCSA in aqueous solution was shear-thinning pseudoplastic, and alginate gel in 1 M CaCl₂ was more elastic than liquid.     

The effect of bentonite concentration on the drug delivery efficacy of a pH-sensitive alginate/bentonite hydrogel

We produced a protein loaded, pH-sensitive alginate-bentonite hydrogel for wound dressings. Alginate is a nontoxic polysaccharide with favorable pH-sensitive properties that make it useful for the intestinal delivery of protein drugs. However, the use of alginate for drug delivery is limited by drug leaching and rapid dissolution of alginate at the higher pH, which may result in lower entrapment efficiency and a burst in the release of entrapped protein drugs. To overcome these problems, we created a novel cross-linked alginate-bentonite hydrogel by combining mineral-rich bentonite with the alginate matrix along with an additive to ensure controlled release. We analyzed the gel in the drug loading process in an aqueous environment by looking at the release profiles of a model protein drug (BSA) from the hydrogel at pH values of 4.5, 5.2 (skin area) and 7.4, 9.2 (wound area). The swelling ratio decreased with bentonite concentration, but did not fall below 6. The rate of drug release was slowest at a pH value of 4.5 and fastest at a pH value of 9.2. The rate of drug release decreased with bentonite concentration. The presence of bentonite prevents the rapid dissolution of alginate at the higher pH, ensuring the controlled release of the entrapped drug.     

氯化钙体系制备的褐藻酸钙凝胶特性的研究

采用氯化钙体系制作的褐藻酸钠凝胶,其性能受氯化钙浓度、温度及褐藻酸钠的甘露糖醛酸(M)及古罗糖醛酸(G)的比值(即M/G)影响较大。当氯化钙溶液的温度为50℃、浓度为2.0%时,凝胶的性能最佳;高G的褐藻酸钙凝胶的拉伸强度优于高M的,但是吸水性能却不如高M的褐藻酸钙凝胶。通过红外光谱分析褐藻酸钠成凝胶前后结构变化,主要是-OH峰位置向高波数方向偏移以及C-H伸缩振动变弱,这是褐藻酸钠与Ca2+之间发生交链的结果。     

Artemia prey size and mode of presentation: Effects on the survival and growth of phyllosoma larvae of southern rock lobster (Jasus edwardsii)

Performance of phyllosoma of thesouthern rock lobster (Jasus edwardsii)was examined after feeding Artemia-baseddiets. Survival and growth of newly-hatchedlarvae cultured to Stage III were lower(p < 0.05) when fed 0.8 mm Artemia than1.5 mm or 2.5 mm Artemia alone or 1.5 mmArtemia in combination with pieces ofmussel (Mytilus edulis planulatus) gonad.This could not be attributed to deficiencies inthe composition of fatty acids but appeared tobe due to the inability of larvae to capturesufficient appropriate-sized, enrichedArtemia for their nutritional requirements.There was an indication that survival andgrowth were higher between Stages III and Vwhen fed 2.5 mm Artemia than 1.5 mmArtemia alone or in combination with musselpieces. However, Stage VI larvae grew to asimilar size at Stage VIII when fed 1.5 mm or2.5 mm Artemia. Unexpectedly, larvae fedthe combination of 1.5 mm Artemia plusmussel supplement had lower survival than foundpreviously, and generally lower than when fed 1.5 mm Artemia alone. This was despitean apparent nutritional profile (lipid contentand fatty acid composition) of mussel more akinto that of newly-hatched phyllosoma thanenriched Artemia. On the other hand,survival and growth to Stage VIII were higherwhen larvae were fed alginate pelletscontaining Artemia than when fed 1.5 mmor 2.5 mm Artemia alone.     

褐藻酸钠涂膜剂的特性研究

对褐藻酸钠凝胶经冻结和解冻处理后的持水能力、凝胶强度、弹性、韧性及状态变化等特性进行了比较试验。结果表明；褐藻酸钠凝胶的这些性质与凝胶体内的钠和钙的比率直接相关；采用２％的褐藻酸钠溶液与５％的氯化钙溶液凝胶化２ｍｉｎ，所形成的凝胶具有很好的涂膜性能。     

Factors affecting mango (Mangifera indica L.) protoplast isolation and culture

The major factors influencing protoplast isolation and culture of mango (Mangifera indica L.) cv. Kensington Pride were investigated. The resultant protocol was used to compare plating efficiency among 4 mango cultivars. Most responses differed between proembryonic masses (PEMs) and leaf sources. Protoplast yields of 15.22 × 10⁶ g⁻¹ from PEMs and 8.68 × 10⁶ g⁻¹ from greenhouse-derived leaves were obtained in a solution of 0.7 M mannitol CPW plus 1.5% cellulase, 1% hemicellulase and 0.75% macerozyme for PEMs or 0.5 M mannitol CPW plus 1.5% cellulose, 1% hemicellulase and 1.5% macerozyme for leaves. Culture in Ca-alginate beads with initial plating densities (IPD) of 2.5 × 10⁴ Pp mL⁻¹ for PEMs and 2.5 × 10⁵ for leaves gave the highest plating efficiencies (FPE). For PEMs 1 mg L⁻¹ 2,4-d and 3.5 mg L⁻¹ kinetin gave an FPE of 2.85% whereas lower kinetin (2 mg L⁻¹) plus 0.5 mg L⁻¹ 6-BAP was most effective for leaves (FPE of 2.12%). Most protoplast mortality occurred during the first week of culture and was more severe in liquid culture. In Ca-alginate beads, protoplast survival at 14 days was higher for PEMs (30%) than leaf (21%) as was the frequency of cell division (17.6% compared to 13.6%). PEMs protoplasts continued development through embryogenesis to in vitro plantlet regeneration whereas leaf protoplasts underwent cell division up to 40-cell colonies but failed to proceed further. For PEMs, polyembryonic cvs. Kensington Pride and Keow Savoey produced higher FPE (1.95%) than monoembryonic cvs. Tommy Atkins and Keitt (1.75%). There was no effect of cultivar for leaf protoplasts.     

Optimization of plant growth-promoting bacteria-assisted phytostabilization of mine tailings

Recent studies have indicated that plant growth-promoting bacteria (PGPB) can improve revegetation of arid mine tailings as measured by increased biomass production. The goals of the present study were first to evaluate how mode of application of known PGPB affects plant growth, and second to evaluate the effect of this inoculation on rhizosphere microbial community structure. PGPB application strategies investigated include preliminary surface sterilization of seeds (a common practice in phytoremediation trials) followed by a comparison of two application methods; immersion and alginate encapsulation. Results with two native desert plant species, Atriplex lentiformis and Buchloe dactyloides, suggest that seed surface sterilization prior to inoculation is not necessary to achieve beneficial effects of introduced PGPB. Both PGPB application techniques generally enhanced plant growth although results were both plant and PGPB specific. These results demonstrate that alginate encapsulation, which allows for long-term storage and easier application to seeds, is an effective way to inoculate PGPB. In addition, the influence of PGPB application on B. dactyloides rhizosphere community structure was evaluated using PCR-DGGE (denaturing gradient gel electrophoresis) analysis of bacterial DNA extracted from rhizosphere samples collected 75 d following planting. A comparative analysis of DGGE profiles was performed using canonical correspondence analysis (CCA). DGGE-CCA showed that rhizosphere community profiles from PGPB-inoculated treatments are significantly different from both uninoculated tailings rhizosphere profiles and profiles from the compost used to amend the tailings. Further, community profiles from B. dactyloides inoculated with the best performing PGPB (Arthro Mix) were significantly different from two other PGPB tested. These results suggest that introduced PGPB have the potential to influence the development of the rhizosphere community structure found in plants grown in mine tailings.     

Survival of,and root colonization by,alginate-encapsulated Pseudomonas fluorescens cells following introduction into soil

Summary The survival of Pseudomonas fluorescens cells encapsulated in alginate beads and colonization of wheat roots was studied in soil microcosms inoculated with the cells in alginate beads of varying composition. Cells encapsulated in beads and introduced into a non-sterile loamy sand survived better than cells added directly to the same soil. A recovery/growth step for the bead-encapsulated cells was added before they were introduced into the soil, in an attempt to obtain optimal population levels in the soil. Further, bacterial populations that grew to the highest density in the beads subsequently showed the highest survival levels in soil. The addition of 3% skim milk, or 3% skim milk and 3% bentonite clay to all bead types consistently resulted in the highest survival of the encapsulated cells in soil. Root colonization by P. fluorescens was generally not impaired by the encapsulation in alginate. One week after inoculation into the soil, encapsulated cells in the various bead types were able to colonize the wheat rhizoplane at high population levels, similar to or exceeding those found when free cells were inoculated. In a second root colonization experiment the wheat rhizoplane was also efficiently colonized 7 weeks after the inoculant cells had been introduced into the soil in different bead types. In both assays, the cells encapsulated in beads amended with skim milk plus bentonite clay showed the highest root colonization rates. It is clear, therefore, that alginate-mediated establishment of inoculants can improve inoculant effectiveness.     

含肉桂油和Nisin的海藻酸钠薄膜保鲜黑鱼性能分析

研究了含有肉桂油和Nisin的海藻酸钠抗菌薄膜保鲜(4±1)℃下贮藏黑鱼鱼肉的效果.鱼肉片被分为:未处理组(CK),海藻酸钠薄膜组(C0),肉桂油海藻酸钠薄膜组(C1),Nisin海藻酸钠薄膜组(C2),肉桂油和Nisin海藻酸钠薄膜组(C3).相对于CK、C0和C2,C1和C3能更好抑制鱼肉总嗜温菌、总嗜冷菌和假单胞菌.C1和C3可显著抑制鱼肉的腐败变质,维持较低pH值、挥发性盐基氮含量和脂肪氧化值,并能抑制鱼肉色泽的变化.C1和C3在维持鱼肉品质上无显著差异.因此,含有肉桂油或者肉桂油和Nisin的海藻酸钠薄膜可有效维持黑鱼的贮藏品质.     

海藻酸钠裂解酶产生菌的筛选及酶活性研究

[目的]筛选海藻酸钠高效降解菌并研究其产酶活性。[方法]以海藻酸钠为唯一碳源,通过驯化培养、初筛、复筛得到一株优势菌,并对该菌的最适生长条件、最适产酶条件及酶的性质作了初步研究。[结果]优选出1株海藻酸钠高效降解菌8号菌株,为革兰氏阴性菌,形态为杆状。该菌在30℃培养72h产酶量最高。海藻酸钠裂解酶作用的最适底物质量分数为1．00％～2．00％,最适pH值为7．o,最适反应温度为4JD℃,温度继续升高,酶活力急剧下降。[结论]为海藻酸钠的有效降解提供了科学依据。