Preparation and characterization of new quaternized carboxymethyl chitosan/rectorite nanocomposite

Quaternized carboxymethyl chitosan (QCMC) was intercalated into the interlayer of rectorite (REC) to prepare QCMC/REC nanocomposite. XRD and TEM results revealed that REC was well dispersed in the polymer matrix and obtained the largest interlayer distance when the mass ratio of QCMC to REC was 2:1. FTIR, NMR and zeta-potential analyses showed that the intercalation of QCMC did not destroy the structure of REC layer, but there were hydrogen-bonding and electrostatic interactions between QCMC and REC. Quaternized chitosan (HTCC)/REC nanocomposite was prepared and studied in parallel. The comparative analysis of the two biopolymer/clay nanocomposites indicated that the free volume and positive charge density of biopolymers were important factors that affected the intercalation of biopolymer into clay. At last, thermal analysis indicated that QCMC/REC nanocomposites had obviously higher thermal stability in comparison with QCMC. This study shows that the combination with clay materials is a functional way to expand the possible application of QCMC as drug controlled-release carriers, antimicrobial agent and pulp-cap.     

Antioxidant capacities and total phenolic contents of 62 fruits

In order to supply new information on the antioxidant function of selected fruits for nutritionists and the general public, antioxidant activities and total phenolic contents of 62 fruits were evaluated using ferric reducing antioxidant power (FRAP) and Trolox equivalent antioxidant capacity (TEAC) assays as well as the Folin–Ciocalteu method, respectively. The correlations between the FRAP value and the TEAC value as well as total phenolic content were also assessed. The results showed that different fruits had diverse antioxidant capacities and the variation was very large, and seven fruits, Chinese date, pomegranate, guava, sweetsop, persimmon, Chinese wampee and plum, possessed the highest antioxidant capacities and total phenolic contents among tested fruits, and could be important dietary sources of natural antioxidants for prevention of diseases caused by oxidative stress.     

Isolation and Characterization of a Glycosyl Hydrolase Family 16 β-Agarase from a Mangrove Soil Metagenomic Library

A mangrove soil metagenomic library was constructed and a β-agarase gene designated as AgaML was isolated by functional screening. The gene encoded for a 659-amino-acids polypeptide with an estimated molecular mass of 71.6 kDa. The deduced polypeptide sequences of AgaML showed the highest identity of 73% with the glycoside hydrolase family 16 β-agarase from Microbulbifer agarilyticus in the GenBank database. AgaML was cloned and highly expressed in Escherichia coli BL21(DE3). The purified recombinant protein, AgaML, showed optimal activity at 50 °C and pH 7.0. The kinetic parameters of K_m and V_max values toward agarose were 4.6 mg·mL⁻¹ and 967.5 μM·min⁻¹·mg⁻¹, respectively. AgaML hydrolyzed the β-1,4-glycosidic linkages of agar to generate neoagarotetraose (NA4) and neoagarohexaose (NA6) as the main products. These characteristics suggest that AgaML has potential application in cosmetic, pharmaceuticals and food industries.     

从浓海水中提取氢氧化镁及改性研究

以浓海水为原料、氢氧化钠为沉淀剂,MOA-9P、硬脂酸钠、十二烷基磺酸钠为改性剂一步合成改性氢氧化镁。通过单因素实验表明MOA-9P添加量3.0%、温度65℃、反应240 min;硬脂酸钠添加量4.0%、温度80℃、反应180 min;十二烷基磺酸钠添加量1.5%、温度70℃、反应210 min改性效果最佳。粒度分析表明改性氢氧化镁粉体分散性明显增强平均粒径降低了8μm。     

Response surface methodology for autolysis parameters optimization of shrimp head and amino acids released during autolysis

Protein hydrolysates were prepared from the head waste of Penaens vannamei, a China seawater major shrimp by autolysis method. Autolysis conditions (viz., temperature, pH and substrate concentration) for preparing protein hydrolysates from the head waste proteins were optimized by response surface methodology (RSM) using a central composite design. Model equation was proposed with regard to the effect of temperature, pH and substrate concentration. Substrate concentration at 23% (w/v), pH at 7.85 and temperature at 50 °C were found to be the optimal conditions to obtain a higher degree of hydrolysis close to 45%. The autolysis reaction was nearly finished in the initial 3 h. The amino acid compositions of the autolysis hydrolysates prepared using the optimized conditions in different time revealed that the hydrolysates can be used as a functional food ingredient or flavor enhancer. Endogenous enzymes in the shrimp heads had a strong autolysis capacity (AC) for releasing threonine, serine, valine, isoleucine, tyrosine, histidine and tryptophan. Endogenous enzymes had a relatively lower AC for releasing cystine and glycine.     

Genetic identification of global commercial sea cucumber species on the basis of mitochondrial DNA sequences

Sea cucumbers are regarded as traditional delicacies, medicine and aphrodisiacs in Asia over many centuries. Generally, sea cucumbers are gutted, boiled and roasted, then preserved through drying, smoking or freezing. Thus, it is very difficult to identify clearly the species of processed sea cucumber on the basis of their morphology. In this work, FINS methodology was developed as a tool to assess the incidence of incorrect labeling of sea cucumbers belonging to family Holothuriidae in commercial food products. The result showed that 7 samples were incorrectly labeled (63.6%). Moreover, the technique allows the genetic identification of more than 40 species from all over the world.     

CXG-1型磁选装置的研制及应用

为满足环境磁学研究、陶瓷和塑料等对原料中磁性杂质的要求,研制了一种自动化程度高、效率高、磁选效果佳的CXG-I型磁选装置。该装置的磁路设计独特,当待选的原材料(浆料、粉末．沉积物等)沿该装置内置与外露的工作磁路流动时,永磁体的强磁场从各个方向将MnO-Fe2O3、Fe3O4和Fe屑等有效地吸附在其表面,由自动冲洗装置把它们清徐。其磁选纯度达到99．92—99．96％,能保证原材料的单纯性,该装置具有多用途、适宜各种场合、节省经费开支等特点,有极大的应用前景。     

复配叶绿素铜钠对草莓的保鲜研究

探讨了复配叶绿素铜钠保鲜涂膜在常温下对草莓的货架期的影响,通过草莓腐烂度、总酸度、VC和可溶性糖的含量变化来评定保鲜效果。结果表明:用叶绿素铜钠、NOCC和丙二醇-1,2复配制成的保鲜涂膜具有较好的水溶性和成膜性,在贮藏期间能有效降低草莓的呼吸强度,减少水分及营养物质的损失,推迟草莓的衰老,使草莓的货架期达到5d,比未处理的草莓货架期延长4d。     

模糊C-均值聚类分析研究大亚湾水质空间分布规律

模糊C-均值聚类方法研究人类活动影响下大亚湾海域水体生态环境空间分布规律．揭示大亚湾水体生态环境空间分布分成两类区域：其一为受人类活动影响为主的大鹏澳、澳头以及大亚湾东北部区域;其二为受湾外南海海水交换影响较大的大亚湾南部、中部和东部海域。模糊C-均值聚类分析作为一种数据信息提取方法,为海洋环境生态研究提供新的方法。