木瓜蛋白酶无载体固定化研究

交联酶聚体(CLEA)是一种新型的无载体固定化技术.以木瓜蛋白酶为模型体系,系统地研究了木瓜蛋白酶的提取纯化方法,固定化制备CLEA的方法以及游离木瓜蛋白酶和CLEA的应用条件、稳定性和不同离子对其活力的影响.结果表明,最适催化温度游离酶为65℃,CLEA最适催化温度为75C;游离酶最适催化pH值为6.6,CLEA最适催化pH值为7.6;米氏常数Km游离酶为1.25μmol/mL,CLEA为0.44μmol/mL.与游离木瓜蛋白酶相比,CLEA的米氏常数Km减小,具有耐高温、活性强、稳定性好等特征,能耐受一定pH值和温度变化,对金属离子不敏感.     

固定化蔗糖酶的研究

利用海藻酸钙凝胶球的包埋作用制备固定化蔗糖酶，并对其性质进行了初步研究，结果表明，游离酶被固定化后，最适pH值为4.0，最适温度为60℃。在高pH值（pH8）和高温下，固定化酶比游离酶更稳定；固定化酶的米氏常数（Km=49.05mmol/L）略大于游离酶（Km=45.45mmol/L）；同时固定化酶明显提高了游离酶的储藏稳定性和操作稳定性。     

生物素-亲和素系统定向固定糖化酶的研究

以生物素-亲和素系统定向固定糖化酶,首先,通过正交试验确定生物素标记糖化酶的最佳条件是:质量浓度为4 mg/mL的酶液2 mL、反应温度20℃、反应pH 4.6、搅拌时间2.5 h;其次,确定了亲和素-磁性琼脂糖微粒的最佳制备条件是:亲和素30μg/mg载体、反应时间20 min、pH 6.6;最后,确定了生物素-亲和素系统定向固定糖化酶的最佳条件是:生物素标记糖化酶液40μL/mg载体、反应时间20 min、反应温度20℃、pH 6.1。此条件下固定化酶活力为1 629.7 U/g,活力回收率为50.3%,固定化酶相对活力为64.7%。对固定化糖化酶的酶学性质的研究表明,固定化酶的最适作用温度65℃,最适作用pH 5.1,米氏常数Km为2.28 mg/mL,较游离糖化酶的米氏常数Km(5.56 mol/L)小,说明其与底物的亲和力提高。固定化酶连续使用5次,酶活仍保持71.8%,固定化酶的半衰期为84 d。     

介孔分子筛SBA-15固定糖化酶的研究

以介孔分子筛SBA-15为载体,戊二醛为交联剂,对糖化酶进行了固定化.考察固定化温度、时间、给酶量、pH值以及戊二醛浓度等因素对固定化效果的影响,并对固定化酶的酶学性质进行了研究.结果表明,糖化酶最佳固定化条件是:酶与载体比例50mg/g、固定化温度25℃、固定化时间4h、pH 5.1、戊二醛体积分数7.5%,此条件下固定化酶活力回收率为56%.固定化酶的最适作用温度为70℃,比游离酶高10℃.最适作用pH 4.1,比游离酶降低0.5个单位.米氏常数Km由原来的0.032mol/L降为0.022mol/L.用超声波对固定化酶进行处理,其酶活力提高了18%.所得最佳超声参数是:超声功率100W,温度70℃,时间5min.     

海藻酸钠-琼脂混合固定化重组右旋糖酐蔗糖酶的研究

以海藻酸钠和琼脂混合物作为载体对右旋糖酐蔗糖酶固定化条件及其特性进行研究,结果表明:4%海藻酸钠和1%琼脂按1:1(V/V)混合后作为载体制备的微球固定化酶表现出持续高活力,在第6批次转化率仍在40%左右;海藻酸钠-琼脂混合载体与酶液体积比为2:1时固定化酶表现出的转化率最高;得到的固定化酶最适反应温度为40℃;最适反应pH值为5.4;最适底物质量浓度为5g/100mL蔗糖;35℃保温1h后剩余酶活力为原来的44%,固定化酶比游离酶的热稳定性好;固定化酶的动力学常数Km=0.02835mol/L。     

介孔分子筛MCM-41固定糖化酶的研究

以介孔分子筛MCM-41为载体、戊二醛为交联剂,对糖化酶进行了固定化.考察了固定化温度和时间、给酶量、pH值以及戊二醛浓度等因素对固定化效果的影响,并对固定化酶的酶学性质进行了研究.结果表明,糖化酶最佳固定化条件是:酶与载体比例为50mg/g、固定化温度20℃、固定化时间8h、pH值6.1、戊二醛浓度7.5％,此条件下固定化酶的相对酶活力为47％.固定化酶的最适作用温度和最适作用pH值没有改变,同游离酶一样,分别为60℃和4.6,米氏常数Km由原来的0.031 mol/L降为0.018mol/L.     

固定化木聚糖酶的比较研究

以海藻酸钠和壳聚糖两种载体对木聚糖酶进行固定化,研究游离酶和固定化酶的性质.结果表明,游离酶的Km=0.546mg/L,以海藻酸钠和壳聚糖为载体的固定化酶的Km分别为38mg/L和0.342mg/L.尽管以壳聚糖固定的酶的最适pH与游离酶相同(都为5.0),但前者的适宜pH范围明显变宽;而经海藻酸钠固定的酶,最适pH向酸性范围移动0.5个pH;两种载体固定的酶最适温度与游离酶相比,都从40℃提高到50℃.实验还表明,固定化酶提高了游离酶的贮藏稳定性.     

漆酶固定化及其性质研究

本文就漆酶的固定化及固定化酶的性质作了初步研究。利用明胶和海藻酸钠的聚合作用与海藻酸钙凝胶球的包埋作用制备固定化漆酶．结果表明：固定化酶米氏常数Km为12.0mg／ml，游离酶米氏常数Km为7．0mg／ml，固定化酶最适温度为40℃，游离酶为30℃．同时固定化酶明显提高了游离酶的耐热性、储藏稳定性和操作稳定性。     

漆酶固定化及其性质研究

本文就漆酶的固定化及固定化酶的性质作了初步研究。利用明胶和海藻酸钠的聚合作用与海藻酸钙凝胶球的包埋作用制备固定化漆酶。结果表明固定化酶米氏常数Km为12.0mg/ml,游离酶米氏常数Km为7.0mg/ml,固定化酶最适温度为40,游离酶为30,同时固定化酶明显提高了游离酶的耐热性、储藏稳定性和操作稳定性。     

定向固定化葡萄糖氧化酶及其酶学性质的研究

戊二醛将伴刀豆球蛋白(ConA)和载体壳聚糖膜交联,然后利用ConA 与葡萄糖氧化酶糖链的特异性结合作用,实现酶的定向固定化。定向固定化的最适条件为戊二醛浓度0.1%、ConA 浓度0.02mg/ml、葡萄糖氧化酶浓度0.08mg/ml。定向固定化葡萄糖氧化酶的最适pH4.0、最适温度57℃,米氏常数Km 为15.84mmol/L,与游离酶及非定向固定化葡萄糖氧化酶比较,定向固定化葡萄糖氧化酶的最适pH 值向酸性范围发生了偏移并有更宽的pH 值适用范围,最适温度提高,与底物的亲和力较大。     

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