来源于Wenyingzhuangia属海洋细菌的一种β-琼胶酶的克隆表达及性质研究

琼胶是一种重要的海洋多糖,其寡糖被证实具有丰富的生理调节功能。该研究拟从微生物基因组出发,利用生物信息学及分子生物学技术发掘新型琼胶酶。以海洋细菌Wenyingzhuangia fucanilytica CZ1127~T为实验材料,从该菌的基因组中发掘出1条潜在的GH16家族β-琼胶酶编码基因序列aga16A,通过分子克隆、异源表达及分离纯化,证实其编码的蛋白Aga16A_Wf具有琼胶酶活力。酶学性质及作用方式分析表明,Aga16A_Wf的最适反应温度(50℃)高于琼胶的凝胶温度,且该酶展现出适冷性;Aga16A_Wf的动力学常数K_m为3.6 g/L,K_(cat)为287.88 s~(-1);该酶为内切型水解酶,最小作用底物为四糖,最小产物为二糖。Aga16A_Wf可作为高效制备琼胶寡糖的工具酶,该酶的获取为琼胶及琼胶寡糖的进一步研究与应用提供了良好支撑。     

一株海洋细菌所产琼胶酶酶学特性的研究

从海水中分离筛选到一株高活力的海洋琼胶降解菌2.2-g。通过硫酸铵盐析、透析袋透析、离子交换柱层析和凝胶柱层析,得到了电泳纯的琼胶酶样品,通过SDS-PAGE电泳,其分子量约为55kDa。该琼胶酶的最适pH值和温度分别为7.0和55℃。Mg2 和Ca2 对酶促反应有较强的促进作用,而Mn2 、Zn2 、NH4 、EDTA和SDS等则有不同程度的抑制作用。酶解产物的质谱和核磁共振谱结果证明,该琼胶酶降解琼胶后得到由新琼二糖、新琼四糖、新琼六糖组成的混合物,证明该琼胶酶为β-琼胶酶。     

两株琼胶酶高产细菌的筛选和鉴定

琼胶酶能降解琼胶多糖,生成琼胶寡糖。这些降解产物在食品等方面有良好的应用价值。本研究从江蓠中分离筛选到两株琼胶酶高产菌,编号分别是2．1-f和1.1-e,它们均为革兰氏阴性菌,呈细杆状。通过API条带分析,它们除了在对柠檬酸盐的利用上存在差别外,其它的生理生化特征完全相同,最终确定它们均为Sphingobacterium multivorum(多食鞘氨醇杆菌),其可信度分别是98．7％和99．5％。     

海洋细菌Vibrio fluvialis的分离鉴定、产琼胶酶条件优化及酶的分离纯化

利用琼胶酶生产琼胶寡糖具有良好的应用前景,然而目前产琼胶酶菌株的性状不稳定、酶活力低等因素限制了琼胶酶的工业化应用。从龙须菜表面筛选出1株具有高琼胶酶活力的菌株A8,利用VITEK 2 GN微生物鉴定系统和16S rRNA基因序列分析,分别进行生理生化和分子生物学鉴定,确定该菌为Vibrio fluvialis A8。通过单因素试验和正交试验确定该菌的最适产酶培养基为:在人工海水中添加2 g/L琼脂、3 g/L半乳糖、3 g/L酵母浸粉、5 g/L Na Cl;最适培养条件为:接种量2%、温度20℃、p H 7. 0。优化后发酵液琼胶酶的活力为21. 80U/m L,是优化前的4. 05倍。Pearson相关性分析表明,菌株生长对其产酶有正相关影响(P <0. 01)。采用(NH4)2SO4分级沉淀和DEAE阴离子交换层析对琼胶酶进行分离纯化,琼胶酶的纯化倍数为3. 26,比活力为141. 52 U/mg,回收率为15. 21%。SDS-PAGE凝胶电泳分析显示,琼胶酶的分子质量约为37 k Da。     

琼胶酶生产菌的筛选、鉴定及其酶学性质的初步研究

从青岛近海的红藻(Gelidium amansii)中分离筛选到一株高活力的海洋琼胶降解菌AT-22，生理生化试验鉴定该细菌为假单胞菌(Pseudomonas sp．)。对其生长、产酶特性和酶活力影响因素的研究结果表明：AT-22所产琼胶酶为诱导酶，0．2％葡萄糖的添加对菌株产酶有抑制作用。该酶作用的最适pH为6．0～7．0，最适温度为40℃，最适底物浓度为1．0％～1．2％，Ca^2 离了的添加对酶促反应有较强的促进作用，而Fe^3 、Mn^2 、Cu^2 和Hg^2 等离子有不同程度的抑制作用。     

响应面法优化嗜热菌Bacillus sp.B Ⅱ-5产琼胶酶的发酵培养基条件

对印度尼西亚热泉菌Bacillus sp.B Ⅱ-5琼胶酶发酵菌株进行发酵条件优化.在前期实验的基础上,选取蛋白胨、酵母粉、琼胶、氯化钙、氯化钠、初始pH值和接种量作为主要菌株产酶影响因素.再利用Plackett-Burman设计筛选出对酶活影响最为显著的3个因素,即蛋白胨、琼胶和氯化钙;采用最陡爬坡实验逼近最大相应区域后再利用Box-Behnken中心设计及响应面分析法对实验数据进行回归分析,得出最优的产酶培养条件.实验表明产酶最优培养的条件为:酵母粉0.4％、蛋白胨0.665％、琼胶1.160‰,氯化钙7.080 mmol/L、初始pH 7.5、接种量1％和氯化钠添加量4‰.对Bacillus sp.BⅡ-5琼胶酶发酵菌株进行发酵条件优化,并且建立数学模型,为该菌发酵琼胶酶在工业生产应用方面奠定了一定的理论基础.     

噬琼胶菌产新琼二糖热稳定琼胶酶的酶学性质及酶解产物的抗氧化活性

利用PCR从噬琼胶菌AL1中扩增琼胶酶基因,将其克隆至表达载体pET-28a;表达产物用亲和层析纯化,研究重组酶的酶学性质;利用薄层色谱和质谱鉴定酶解产物,并测定酶解产物的还原能力和清除DPPH、ABTS+和·OH自由基的能力,分析酶解产物的抗氧化活性.结果表明,来自噬琼胶菌AL1重组琼胶酶的分子质量为105 ku.该...     

基于理性设计提高产微球茎菌AG1琼胶酶的热稳定性

目的：对产微球茎菌AG1的琼胶酶基因进行理性化设计,获得酶热稳定性高的突变酶。方法：利用PoPMuSiC在线分析工具对AG1的琼胶酶序列进行分析,选择提高酶热稳定性的突变位点,利用重叠延伸PCR技术获得突变体基因,并对突变酶进行诱导表达、纯化及性质鉴定。结果：通过筛选获得琼胶酶热稳定性高的突变体D136N。在60 ℃下处理1 h,该突变酶保持87%的残余活力,而野生型为19%的残余活力,说明突变体D136N具有较好的热稳定性。酶的三维结构模拟显示,野生型Asp136与Asn255形成两个氢键,与Tyr282形成一个氢键;突变后的Asn136和Asn255形成3个氢键,与Tyr282形成一个氢键,还与Ala134形成了一个氢键,突变酶的136位氨基酸与周围氨基酸形成更多的氢键。结论：通过理性化设计获得产微球茎菌AG1琼胶酶热稳定性高的突变体D136N,对改善酶的性质,扩大琼胶酶的应用范围,以及研究琼胶酶结构与功能关系具有重要意义。     

海洋细菌Sphingomonas sp. Q2产琼胶酶发酵条件优化、酶学性质及降解产物研究

本研究旨在对从江蓠中筛选获得的Sphingomonas sp. Q2菌株产琼胶酶能力条件进行优化并对其酶学性质及降解产物进行研究。通过响应面法对发酵条件进行优化,采用硫酸铵沉淀、离子交换层析和凝胶层析等方法对发酵所得酶液进行纯化并对纯化后的酶液进行酶学性质研究。发酵优化结果表明该菌株产琼胶酶的最佳培养基组成为：琼脂4.42 g/L、磷酸氢二钾1.30 g/L、氯化钠10.51 g/L。优化后的酶活力为1085.71 U/mL,较优化前提高了1.58倍。纯化后的琼胶酶比活为112048.82 U/mg,纯化倍数为7倍,回收率为48.04%。酶学性质结果表明该酶最适反应温度为40℃,最适pH为6.5,且在最适温度下保存8 h,酶活仍保持在90%以上。MS和¹³C-NMR结果表明,该琼胶酶的降解产物主要为新琼四糖。该琼胶酶具有良好的热稳定性及较高的酶活力,为琼胶寡糖的开发制备提供了基础。     

产琼胶酶菌株NBRC102603发酵条件优化及酶的分离纯化

通过正交试验对产琼胶酶海洋菌株NBRC102603发酵条件进行了优化,优化得到的发酵产酶条件为:蛋白胨浓度5.0 g/L、酵母膏浓度1.25 g/L、琼胶浓度4.0 g/L、装瓶量100 mL、接种量1%、转速150 r/min,28℃下发酵48 h后酶活力达到58.94 U/mL,比未优化前提高了2.08倍。经纯化得到琼胶酶A和琼胶酶B,琼胶酶A纯化倍数为17.29倍,酶比活力为870.51 U/mg;琼胶酶B纯化倍数为16.65倍,酶比活力为838.39 U/mg。纯化后琼胶酶经SDS-PAGE检测,显示为单一条带,其相对分子质量酶A约为83.6 ku、酶B约为36.8 ku。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the     

Chinese CTP Market

According to Printing and Printing Equipment Industries Association of China（PEIAC）＇s statistics to the plate manufucturer in China, in 2013, the actual offset plate production has reached 346 million square meters in China. Among them, the CTP production volume was 245 million square meters, up by 11% than that of last year; the total sales of the CTP plate was 239 million square meters, up by 13%.     

Preparatory Work of Print China 2015 is Going Smoothly

正Held at Guangdong Modern International Exhibition Center,Print China 2015 will cover 7exhibition halls,besides the original Hall No.3,4,5,6,7,the newly built F zone of Hall 3 will be used too.The total area will be140,000 square meters.Hall 3:Offset and large printing equipment,package printing equipment,post press