葡萄糖和蛋白胨对绿色木霉纤维素酶系分泌特性的影响

采用正交试验法分析出绿色木霉3.3711液体发酵产纤维素酶系各组分的最适酶解条件,其组合分别为C1(pH 5.0、45℃),Cx(pH 3.5、55℃)和βG(pH 4.5、65℃)。在液体基础产酶培养基发酵条件下,三种组分酶的最高酶活分别为53.6、185.2、79.3 u/mL,比酶活分别为46.6、167.7、71.8 u/mg,最高的酶活形成时间分别为9、10、10 d。添加质量分数0.0005~0.003的葡萄糖,三种组分酶最高酶活分别降低了27.4%~38.4%、25.5%~35.5%、14.0%~52.3%,C1和Cx的最高酶活形成时间分别缩短为4~7、5 d,C1和βG比酶活分别降低了20.8%~35.4%、25.8%~64.5%;添加质量分数0.0005~0.01的蛋白胨,提高了C1和Cx最高酶活(分别为0.9%~199.6%、2.1%~45.1%),缩短了C1和Cx的最高酶活形成时间(分别为4~7、4 d),降低了βG的最高酶活(5.9%~34.2%)和比酶活(35.2%~87.3%),对C1和Cx比酶活的增减效应存在浓度依赖性,质量分数0.0005时分别提高50.0%、65.4%。两种添加物均能明显改变C1和Cx的分泌变化规律,对βG酶影响极小。     

β-1,3葡聚糖酶高产菌株的筛选及其产酶条件研究

从土壤中分离筛选出一株β-1，3葡聚糖酶活较高的菌株，编号为M014，初步鉴定为木霉。研究了碳源、氮源、培养温度与时间等因素对M014产酶的影响。实验结果表明，MOl4在含3％茯苓粉、0．5％酵母膏及一些无机盐的液体培养基中(pH6．0)，于30℃，150r／min振摇培养6d，β-1，3葡聚糖酶活最高，达到4．95U／ml。另外，还就β-1,3葡聚糖酶的酶解条件进行了研究，结果显示，β-1,3葡聚糖酶的最适反应pH为4．5,最适反应温度为60℃.粗酶液在40℃和50℃保温12h，酶活基本稳定，最适反应温度为60℃保温时，酶活迅速下降。     

白腐菌发酵培养及诱导剂对漆酶合成的影响

研究了碳源、氮源及诱导剂添加方式对白腐菌P.conchatus液体培养产漆酶的影响.结果表明,当碳源为葡萄糖,氮源为酵母膏,C/N比为15∶1时,P.conchatus合成漆酶酶活达到8795U·L-1;在初始培养基中,添加1.5％麦麸与1 mmol/L Cu2+共同诱导漆酶合成,酶活可达到51004U·L-1;将Cu2的添加时间改在发酵后第4d,添加量为3mmol/L,其他条件不变,漆酶酶活达到101968U·L-1,比在初始培养基中添加1 mmol/L Cu2+所达到的酶活高了近两倍.     

碳源对里氏木霉纤维素酶诱导合成的影响

纤维素酶是诱导酶,理想的碳源应该既能提供菌种生长所需能量,又能诱导纤维素酶基因的高效表达。试验中分别以葡萄糖经过转糖苷反应后制备的复合糖(F)、微晶纤维素(C)以及上述两者(1∶2)的混合物(M)为里氏木霉(Trichoderma Reesei ZU-04)的碳源,在液态深层发酵条件下生产纤维素酶。对纤维素酶酶系组成的研究结果表明:F碳源诱导作用下,内切型-β-葡聚糖酶(Cx酶)和外切型-β-葡聚糖酶(C1酶)的活力在发酵初期上升很快,通常在40h左右达到峰值,此后活力呈下降趋势,而β-葡萄糖苷酶(CB酶)的活力始终较低;C碳源诱导作用下,Cx、C1和CB酶的活力上升在发酵初期比较缓慢,但持续时间长、后劲足;在采用M碳源的情况下,Cx、C1酶的初始合成速度较快,且2种酶的活力在较长时间内保持上升趋势。与F和C碳源相比,Cx酶活力分别提高了78.2%和51.9%,C1酶活力分别提高了20.6%和6.5%,但对CB酶的生产而言,M碳源略低于C碳源,F碳源最差。进一步研究了碳源对纤维素酶总活力(滤纸酶活力)的影响,结果显示:在采用F碳源的条件下,发酵6h即可检测到滤纸酶活力,在36h达到峰值1.6IU/mL,此后活力不再上升;在采用C碳源时,发酵初期酶活力上升缓慢,产酶周期较长,滤纸酶活力在144h达到峰值3.96IU/mL;而M碳源可结合两者优势,使纤维素酶活力和产率都能达到较高的水平。研究结果对于定向调控纤维素酶的酶系组成,提高纤维素酶的生产效率具有重要意义。     

Thielavia terrestris产纤维素酶液态发酵条件的优化

以Thielavia terrestris(ATCC38088)为出发菌株,通过单因素试验研究不同碳源(CMC-Na、Avicel、稻草粉、滤纸、麦麸、可溶性淀粉、葡萄糖)、不同氮源(牛肉膏、蛋白胨、氯化铵、黄豆饼粉、酵母提取物、硫酸铵)、不同的初始pH(3.0⁶.0)等培养条件对该菌株滤纸酶活的影响。在此基础上,通过正交试验对该菌株产纤维素酶的条件进行了优化。结果表明,其产纤维素酶的佳条件为:以2.5%的麦麸为碳源、以2.0%的黄豆饼粉为氮源,初始pH值为4.0,在此条件下,45℃产酶发酵培养48 h,滤纸酶活力可达1.39 U/mL。     

产β-葡聚糖酶耐盐鲁氏酵母的筛选及鉴定

从农家自制辣椒酱中分离纯化了一株耐盐酵母,通过β-1,3葡聚糖酶鉴定(刚果红染色法)确定其具有合成、分泌胞外β-1,3葡聚糖酶特性。Na Cl耐受性研究确定其具有高耐盐性,能经144 h的适应期后在24%Na Cl的培养基B中稳定生长120 h。经26s r RNA基因序列分析鉴定为鲁氏酵母A(Z.Rouxii A)。Z.Rouxii A发酵培养中存在二次生长现象,其生物量在24 h和48 h达到峰值,分别比18 h的6.38 g/L提高了46.55%和87.15%,而21 h后葡萄糖浓度仅维持在1.57 g/L左右,说明:Z.Rouxii A生长过程中合成、分泌的β-葡聚糖酶持续降解发酵培养基中添加的β-1,3-1,6-葡聚糖,为其二次生长提供了碳源和能源。Z.Rouxii A的β-1,3-葡聚糖酶活性曲线与生长曲线基本趋势一致,最大酶活性随着菌体自溶(12 h、24 h和48 h)而迅速降低,48 h达到酶活峰值15.23 U/m L,说明:Z.Rouxii A的β-1,3-葡聚糖酶合成与细胞生长偶联。以上数据确认该菌为产β-葡聚糖酶高耐盐鲁氏酵母。     

β-葡萄糖苷酶对大麦芽发酵度的影响

本研究将3种纤维素复合酶(羧甲基纤维素酶活与β-葡聚糖酶酶活一样,β-葡萄糖苷酶酶活不同),添加到麦芽糖化过程中。在麦汁中加入酿酒酵母进行发酵,对发酵过程中葡萄糖,麦芽糖,麦芽三糖以及乙醇的含量进行了跟踪测定。在最终啤酒发酵液中,未加酶与三种加酶(β-葡萄糖苷酶加量分别为35﹑125﹑200 IU/kg)组乙醇含量分别为4.68﹑4.98﹑5.05﹑5.22 g/100mL,说明添加β-葡萄糖苷酶能将纤维素β-葡聚糖寡糖进一步分解成为葡萄糖,从而被酵母利用产生更多的乙醇。     

酶法测定大麦提取物中β-葡聚糖含量的研究

在国际β-葡聚糖酶法测定β-葡聚糖含量的基础上,用纤维素酶代替昆布多糖水解酶水解β-葡聚糖,用β-葡聚糖酶代替β-葡萄糖苷酶,用苯酚-硫酸法代替葡萄糖试剂盒法测定β-葡聚糖酶解后得到葡萄糖含量,设计了适合我国应用的β-葡聚糖酶法测定方法。此法测定过程为：1．5mL浓度为60μg/mL的标准β-葡聚糖和一定浓度的样品,用浓度为50U/mL纤维素酶0．5mL酶解60min；然后用蒸馏水稀释至30mL,从中吸取0．5mL到另一试管,再加入浓度为2U/mLβ-葡聚糖酶1mL,作用15min后,用苯酚-硫酸法测定标准β-葡聚糖和样品酶解液中葡萄糖含量,计算出样品中β-葡聚糖的含量。     

白耙齿菌F036液态发酵产纤维素酶条件优化及纤维素酶酶学性质初步研究

研究了白耙齿菌F036产纤维素酶液态发酵条件及部分酶活性质。结果表明,其产酶最佳氮源为蛋白胨,初始p H值为5. 0,发酵时间为4 d。在此条件下,FPA、C1、Cx及βG酶酶活分别达到2. 058、1. 401、163. 982和3. 079 IU/m L,其中Cx酶酶活最高。各纤维素酶最佳酶促反应p H值均为5. 0,温度均为50℃。当金属离子质量浓度为0. 15 mg/m L时,Fe~(2+)、Co~(2+)、K+和Ca~(2+)对Cx酶酶活的促进率分别为28. 95%、11. 69%、1. 53%和1. 19%; Zn~(2+)、Cu~(2+)、Mg~(2+)和Fe3+对Cx酶酶活的抑制率分别为12. 09%、11. 03%、9. 70%和6. 83%。可见,高产Cx酶白耙齿菌F036菌株在真菌协同发酵降解纤维素应用方面可能具有潜在的价值。     

果胶酶高产菌株的激光选育及发酵条件的优化

利用氦氖激光诱变原生质体筛选到了一株产果胶酶性能稳定且酶活明显提高的突变株ZH-2。其最适发酵条件为：以2％桔皮粉＋1％乳糖作碳源，以1％（NH4）2SO4＋0．3％酵母膏作氮源，在起始pH7．0，33℃摇床发酵32h左右达产酶高峰。分析ZH-2所产果胶酶的性质得出，酶作用最适条件为：pH6．5，50℃，以聚半乳糖醛酸为底物，酶的热稳定性实验显示，50℃保温60min后，酶活力基本不变。     

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