水相体系中固定化Acetobacter sp.CCTCC M209061细胞催化(S)-3-氯苯丙醇不对称合成

光学纯的3-氯苯丙醇是合成抗抑郁类药物的重要中间体。本论文报道了水相体系中固定化Acetobacter sp.CCTCC M209061细胞高效、高选择性地催化3-氯苯丙酮不对称还原为(S)-3-氯苯丙醇,采用聚乙烯醇与海藻酸钠的混合载体对醋酸杆菌细胞进行固定化,所得的固定化细胞的稳定性(热稳定性、p H稳定性及操作稳定性)均明显优于游离细胞。同时,固定化后的微生物细胞具有较好的重复利用性,连续反应3个批次后固定化细胞仍保留了80.0%以上的活性,而游离细胞的相对活性则小于20%。在所研究的体系中,葡萄糖为该反应的最佳辅底物,其最适浓度为50.0 mmol/L;该反应体系中的最适缓冲液p H值、反应温度、底物浓度分别为5.5、30℃和3.0 mmol/L。在此条件下,反应的初速度、产率以及产物的e.e.值依次为1.77 m M/h,88.9%和99.0%以上。     

重组葡萄糖脱氢酶的酶学性质及其偶联辅酶再生

为解决生物催化氧化还原反应中辅酶循环问题,人工合成密码子优化后的嗜酸热源体Thermoplasma acidophilum葡萄糖脱氢酶基因Sygdh,于E.coli BL21(DE3)中表达,粗酶液经镍柱亲和层析获得纯化的重组葡萄糖脱氢酶SyGDH。SDS-PAGE显示相对分子质量为41.0 kDa。酶学性质分析表明:该酶的最适pH值为7.5,在pH 6.0~8.0稳定;最适反应温度为40℃,在55℃以下稳定;最适条件下其比活性达4.5 U/mg;Zn2+对其有明显激活作用;该酶对NADP+的亲和力大于NAD+且对大多数有机溶剂有良好的耐受性;对D-葡萄糖的Km和Vmax值分别为28.2 mmol/L和6.5 U/mg。在葡萄糖脱氢酶与羰基还原酶偶联构建的NADPH辅酶循环体系中,以4-氯乙酰乙酸乙酯为底物,羰基还原酶催化产物4-氯-3-羟基丁酸乙酯的产率为99.0%,是未添加葡萄糖脱氢酶时产物产率的3.11倍,表明重组SyGDH具有为生物催化氧化还原反应提供辅酶NADPH再生的能力。     

水/正己烷双相体系全细胞合成D-苯基丙酸的研究

利用前期筛选出的耐受苯基乳酸的突变菌株E. coli Z2016 (CCTCC保藏编号为M2016332),在水相和有机溶剂正己烷组成的双相体系中转化生产苯基乳酸。实验还研究了转化温度、摇床转速、底物浓度、湿菌体浓度和有机溶剂正己烷的体积分数对PLA产量的影响。当转化温度为40℃、摇床转速为300 r/min、底物浓度和耐受PLA突变菌株E. coli Z2016菌体浓度均为15 g/L、正己烷的体积分数为40%的时候,PLA的产量最大,为10. 9±0. 08 g/L/h。     

醋酸杆菌产乙醇脱氢酶发酵条件的研究

选择一株醋酸杆茵Acetobacter sp.CCTCC M209061,通过单因素和正交实验确定醋酸杆菌产乙醇脱氢酶(Alcohol Dehydrogenase,ADH)的最优发酵条件.结果表明,产ADH的最优培养条件为温度30℃、pH值6.0、通气量为100 mL/250 mL、接种量为8%,在此条件下发酵培养24 h,发酵液酶活可达0.340 U/mL.     

氧化还原酶共表达耦联催化合成(R)-4-甲氧基-1-苯乙醇

针对生物催化不对称还原反应中必需辅酶再生及反应效率问题,以抗过敏药物的重要中间体化合物光学活性4-甲氧基-1-苯乙醇为目标产物,构建了羰基还原酶基因SCRII-A220D和葡萄糖脱氢酶基因gdh共表达的重组菌株E.coli BL21/p ET-SCRII-A220D-SD-AS-gdh。该双酶共表达耦联系统中,羰基还原酶与葡萄糖脱氢酶酶活水平相当,有利于双酶耦联催化反应的进行。通过考察反应体系和环境条件对该共表达耦联系统催化反应的影响,发现底物质量浓度、细胞质量浓度,及反应体系温度和p H值等条件对最终产物合成效率的影响规律。在较优条件下,产物(R)-4-甲氧基-1-苯乙醇的光学纯度达到98%,产率达到82%。     

Acetobacter sp.驯化选育及固定化生产3-羟基丙酸

3-羟基丙酸作为最有价值的平台化合物之一,其自身及诸多衍生化合物被广泛应用于材料、纺织、食品工业及生物医药领域。利用Acetobacter sp.生物催化1,3-丙二醇(1,3-PDO)合成3-羟基丙酸(3-hydroxypropionic acid,3-HP)的性能,通过梯度增加培养基中1,3-PDO浓度驯化选育Acetobacter sp.,有效提高了该菌对底物的耐受性;同时利用固定化细胞的方法提高菌株对底物的耐受性和3-HP转化率,当包埋材料为30 g/L海藻酸钠和聚乙烯醇混合物、颗粒粒径2 mm,添加0.1 mmol/L Fe2+时,固定化细胞表现出最大的催化活性。10 g/L(CDW)固定化细胞可催化70 g/L 1,3-PDO为66.95 g/L 3-HP,催化水平是静息细胞的1.32倍,且固定化细胞经50 g/L底物循环利用5次后,3-HP摩尔转化率仍保持80.65%。固定化的醋酸菌类生物催化剂为工业上3-HP的实际生产提供了一种新可能。     

基于Gluconobacter oxydans膜结合脱氢酶的静息细胞催化合成2-酮基-D-葡萄糖酸

基于G.oxydans DSM2003膜结合葡萄糖酸-2-脱氢酶（GA-2-DH）的催化特性,利用静息细胞催化技术合成D-异抗坏血酸（EA）的主要前体2-酮基-D-葡萄糖酸（2-KGA）。利用高浓度底物自适应筛选技术,筛选到高产2-KGA菌株并对其摇瓶催化进行优化,优化后最适条件为：温度30℃,pH6.0,细胞浓度20g/L,底物浓度1100mmol/L,摇床转速250rmin,此时时空产率为24.68mmol/L/h;摇瓶优化工艺基础上在7L发酵罐中对重点影响参数（转速与底物浓度）进行了进一步优化,优化后2-KGA的时空产率提高到74mmol/L/h,并且催化细胞可有效重复利用3次。     

树脂原位吸附促进高浓度底物不对称拆分dl-薄荷醇

以洋葱布克氏菌(Burkholderia cepacia)全细胞为催化剂,考察添加吸附树脂对酯酶酶法不对称拆分dl-薄荷醇的影响.通过对比6种弱极性的树脂吸附性能,选择出了对产物薄荷醇有较好吸附性能的树脂HZ-845.可以显著降低产物薄荷醇对不对称拆分反应的抑制作用,提高反应的底物初始浓度.在底物浓度提高6倍的条件下,在较短的时间内达到良好的转化率和产物光学纯度水平.在60g/L的底物初始浓度下,反应2h后添加树脂,反应24h,产物l-薄荷醇的产物e.e.值和反应转化率分别为98%和45%.     

醇脱氢酶不对称还原2-[3-[3-[2-(7-氯-2-喹啉基)乙烯基]苯基]-3-羟基丙基]苯甲酸甲酯

孟鲁司特钠是主要的抗哮喘药物之一,2-[3-(S)-[3-[2-(7-氯-2-喹啉基)乙烯基]苯基]-3-羟基丙基]苯甲酸甲酯是孟鲁斯特钠的关键手性砌块.以实验室筛选到的醇脱氢酶不对称还原2-[3-[3-[2-(7-氯-2-喹啉基)乙烯基]苯基-3-羟基丙基]苯甲酸甲酯,制备2-[3-(S)-[3-[2-(7-氯-2-喹啉基)乙烯基]苯基-3-羟基丙基]苯甲酸甲酯.在辅酶添加量为0.1 g/L,底物浓度为219.3 mmol/L,菌体用量为30 g/L,pH 7.5,45 ℃反应7h后,底物转化率达到100％,时空产率为31.2 mmol/(L·h),产物e.e.值大于99.9％.通过分批补料,反应5h,底物转化率达到100％,e.e.＞99.9％,时空产率达43.7 mmol/(L,h),是一次性投料的1.4倍.     

面包酵母催化溶剂相不对称还原合成(R)-2-羟基-4-苯基丁酸乙酯

研究有机溶剂中面包酵母催化2-氧代-4-苯基丁酸乙酯（OPBE）不对称还原合成（R）-2-羟基-4-苯基丁酸乙酯（（R）-HPBE），分别考察有机溶剂种类、初始水含量、初始底物浓度、缓冲液pH值和添加剂等因素对OPBE转化率（COPBE）、HPBE产率（YHPBE）及（R）-HPBE的光学纯度（ee％）的影响。实验结果表明，乙醚为适宜反应介质，适宜pH为中性；反应初始水含量和初始底物浓度分别以ω（H2O）=30g／L、c（OPBE）=5mmol／L为佳。添加α-氯代苯乙酮（α—PC）对酵母预处理2h后，（R）-HPBE的PP从35．52％提高为82．25％，COPBE和YHPBE分别从75．29％和46．02％提高到98．51％和75．82％。     

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