戊二醛交联法固定扩展青霉脂肪酶的研究

以海藻酸钠为载体,戊二醛为交联剂,采用交联吸附法固定扩展青霉脂肪酶。通过单因素试验和正交试验考察固定化主要因素对固定化酶活力的影响,优化固定化条件。结果表明,海藻酸钠浓度为3%、氯化钙为1%、戊二醛浓度为2.5%的条件下,酶浓度为0.03g/mL,pH为10.0,固定温度为40℃,固定时间为30min,该条件下固定化酶活最高为22895u/g,酶活回收率达到67.57%。在有机体系中,固定化脂肪酶的酯化能力明显高于游离态脂肪酶。在重复利用9次后,固定化脂肪酶的酶活降为初始状态的50%。     

Fe_3O_4-SiO_2载体制备和脂肪酶固定化条件优化

通过共沉淀法和溶胶-凝胶法制备了Fe3O4-Si O2磁性纳米粒子,将Fe3O4-Si O2磁性纳米粒子表面进行氨基化修饰得到磁性纳米复合载体,用扫描电子显微镜和傅里叶变换红外光谱对载体进行了表征。通过考察加酶量、戊二醛浓度,固定化时间和温度等因素对蛋白固载率和脂肪酶活力的影响,获得了脂肪酶固定化的最适条件。在0.02g/m L脂肪酶液加入量为8.30m L,戊二醛浓度为8.20%时,在温度24℃条件下,固定化4h,制备的固定化脂肪酶酶活3449U/g。     

海藻酸钠包埋法制备固定化脂肪酶研究

研究了以海藻酸钠为载体,用包埋法制备固定化脂肪酶的条件,将一定量的海藻酸钠用蒸馏水加热溶解,将500mg脂肪酶溶解在pH=6的缓冲溶液中,然后两者混合均匀,用注射器将海藻酸钠酶液逐滴到1%的无菌CaCl2溶液中,搅拌条件下室温固定1h,过滤,洗涤,干燥,得球状固定化脂肪酶。试验表明,此固定化酶具有良好的耐热性能,在60℃下加热固定化脂肪酶和游离脂肪酶1.5h,固定化酶活力仅损失30%,而游离脂肪酶的酶活只为原来的18%。固定化脂肪酶还有良好的可操作性,连续使用反应10次,固定化脂肪酶的酶活依然为初始酶活的95%。     

海藻酸钠与羧甲基纤维素钠固定化高温碱性脂肪酶

以海藻酸钠和羧甲基纤维素钠为复合载体,研究包埋法固定化毕赤酵母高温碱性脂肪酶。通过单因素试验考察了不同载体、载体浓度、酶与载体配比等因子对脂肪酶固定化的影响,并采用正交试验对脂肪酶固定化条件进行了优化。结果表明,包埋法固定化脂肪酶的最优条件为海藻酸钠含量1.0%、羧甲基纤维素钠含量0.25%、加酶量50 U/(g载体)、CaCl2浓度0.4 mol/L,固定化时间40 min。在最优固定化条件下,固定化脂肪酶酶活收率达99.50%。     

新型液态固定化脂肪酶制备及其稳定性的研究

传统的固态固定化脂肪酶存在载体易破碎、制备成本高等问题,制约了其工业应用。利用前期开发的三液相体系中相作为脂肪酶液态固定化载体,研究了不同种类的成相物质、成相物质的比例以及不同种类的脂肪酶对液态固定化酶回收率的影响。同时考察了该液态固定化载体固定脂肪酶的稳定性。结果表明:正己烷/PEG400/Na_2SO_4三液相体系中相为更优的液态固定化酶载体;最优的制备条件为PEG400比例20%、Na_2SO_4比例14%,此条件下AY30脂肪酶的回收率可达98%以上,其他类型脂肪酶中相回收率均大于90%;该液态固定化载体在30℃的环境下能有效保持脂肪酶的催化活性,保护效果在不同温度下均明显优于传统水-有机溶剂体系;同时,脂肪酶在此液态固定化载体中的保藏稳定性也优于水环境,低温保藏2周后仍能保留约78. 4%的酶活力,体现出较好的保藏稳定性。     

固定化米黑根毛霉脂肪酶的制备工艺优化及其酶学性质北大核心CSCD

以海藻酸钠-羧甲基纤维素钠(CMC)为复合载体,戊二醛为交联剂,探究了包埋-交联法制备固定化米黑根毛霉脂肪酶的最佳工艺条件,并对固定化米黑根毛霉脂肪酶的酶学性质进行分析。结果表明,制备固定化米黑根毛霉脂肪酶的最佳工艺条件为海藻酸钠质量分数2.5%、CMC质量分数1.5%、脂肪酶液浓度800 U/mL、CaCl_(2)质量分数5%、戊二醛质量分数0.03%、交联固定化时间30 min,在此条件下固定化米黑根毛霉脂肪酶的酶活力为245.58 U/g,与游离脂肪酶相比,固定化脂肪酶热稳定性和pH稳定性均有所提高。交联剂戊二醛的添加可以提高固定化脂肪酶的操作稳定性和储存稳定性,在重复使用7次后相对酶活力保持在57.39%,在4℃下存放7周后相对酶活力为61.89%。包埋-交联法制备的固定化米黑根毛霉脂肪酶具有更好的稳定性和适应性,为实现植物油酶法酯化脱酸工业化生产提供参考。     

聚苯乙烯微球固定化海洋脂肪酶YS2071及其性能研究

采用6种不同孔径和亲疏水性的聚苯乙烯微球,通过吸附法固定化脂肪酶YS2071,筛选得到最佳载体,对固定化条件进行了优化并对其性能进行了研究。结果表明:粒径范围0. 6～1μm的氨基聚苯乙烯微球B具有最佳的固定化效果,在酶质量浓度5 mg/m L、p H 10、固定化温度20℃、振荡转速250 r/min、吸附时间6 h条件下,酶活回收率达到42. 82%;与YS2071脂肪酶游离酶相比,经固定化后的载体脂肪酶的温度稳定性、金属离子稳定性、有机溶剂稳定性、pH稳定性均明显增强; 25℃存储30 d后,固定化酶酶活保留率比游离酶酶活保留率提高了15. 09个百分点;固定化酶重复使用5次后,酶活保留率为63. 77%。     

磁性壳聚糖微球固定化脂肪酶研究

以磁性壳聚糖微球为载体,通过戊二醛交联进行脂肪酶固定化,对影响脂肪酶固定化各种因素进行考察,确定最佳条件,并比较游离酶与固定化酶pH和热稳定性。结果表明,固定化适宜条件为:脂肪酶加入量5.0 mg/100 mg载体、温度40℃、时间5 h、pH 8.04、戊二醛浓度10%、最高固载率可达90.56%,酶活4034 U/g载体;与游离酶相比,固定化酶pH和热稳定性都有较宽适用范围。     

脂肪酶固定化工艺优化及其酶学性质研究

以D-101、AB-8和S-8三种大孔树脂为载体,进行黑曲霉脂肪酶的固定化研究。根据脂肪酶的固定化率及活力回收率,确定D-101为固定化载体。经响应曲面法优化得脂肪酶的固定化工艺:以5 g经预处理的D-101为载体,加入9.0 m L酶液(20 mg/m L),p H 7.6,39℃下吸附4.3 h,脂肪酶固定化率为95.11%,固定化脂肪酶活力回收率为101.36%。固定化酶最适反应温度升高2℃,最适p H不变,固定化脂肪酶的酸碱稳定性和热稳定性均优于游离酶。     

响应面法优化磁性壳状固定化脂肪酶制备工艺研究

目的 优化磁性壳状脂肪酶固定化工艺,并利用磁性固定化脂肪酶快速筛选荷叶中具有脂肪酶抑制作用的活性成分。方法 采用一锅法制备Fe3O4-壳聚糖作为固定化载体,采用响应面设计法优化以聚乙二醇二缩水甘油醚为交联剂的脂肪酶固定化工艺,确定反应pH、温度、加酶量和时间,并进行固定化脂肪酶表征与活性测定;固定化脂肪酶与荷叶样品液反应30 min后,磁分离,甲醇洗脱后采用高效液相色谱法(high performance liquid chromatography, HPLC)分析。结果 以固载率、酶活、酶活回收率为响应值,确定最佳制备工艺为pH 8.1、温度40℃、酶质量浓度2.55 mg/mL、反应时间2.3 h,固载率均值为85%、酶活均值为5.44 U/mg、酶活回收率均值为81%;利用固定化脂肪酶快速筛选发现荷叶中荷叶碱与2-羟基-1-甲氧基阿朴啡具有较高的脂肪酶抑制活性。结论 本研究优选的脂肪酶固定化制备流程简捷,脂肪酶利用率提高,易分离,有助于荷叶等药食两用原料中脂肪酶抑制成分的快速筛选研究。     

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.     

Chlorohydrins of bisphenol A diglycidyl ether (BADGE) and of bisphenol F diglycidyl ether (BFDGE) in canned foods and ready-to-drink coffees from the Japanese market

BADGE.2HCl and BFDGE.2HCl were determined in 28 samples of ready-to-drink canned coffee and 18 samples of canned vegetables (10 corn, 5 tomatoes and 3 others), all from the Japanese market. HPLC was used as the principal analytical method and GCMS for confirmation of relevant LC fractions. BADGE.2HCl was found to be present in one canned coffee and five samples of corn, BFDGE.2HCl in four samples of canned tomatoes and in one canned corn. No sample was found which exceeded the 1mg/kg limit of the EU for the BADGE chlorohydrins. However the highest concentration was found for the sum of BFDGE.2HCl and BFDGE.HCl.H₂O at a level of 1.5mg/kg. A Beilstein test confirmed that all cans containing foods contaminated with BADGE.2HCl or BFDGE.2HCl had at lest one part coated with a PVC organosol.     

European priorities for research to support legislation in the area of food contact materials and articles

A strong science base is required to underpin the planning and decision-making process involved in determining future European community legislation on materials and articles in contact with food. Significant progress has been made in the past 5 years in European funded work in this area, with many developments contributing to a much better understanding of the migration process, and better and simpler approaches to food control. In this paper this progress is reviewed against previously identified work-areas (identified in 1994) and conclusions are reached about future requirements for R&D to support legislation on food contact materials and articles over the next 5 or so years.     

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