固定化酵母发酵产酒精载体选择的研究

以海藻酸钙和甘蔗块为载体固定酵母细胞,进行蔗汁和废糖蜜酒精发酵。结果表明,以甘蔗汁为发酵培养基时甘蔗块固定化酵母发酵液中平均残糖锤度(20℃)比海藻酸钙包埋酵母发酵低0.36,酒精平均体积分数比海藻酸钙包埋酵母发酵高0.20%;以废糖蜜为发酵培养基时甘蔗块固定化酵母发酵液中平均残糖锤度(20℃)比海藻酸钙包埋酵母发酵低0.43,酒精平均体积分数比海藻酸钙包埋酵母发酵高0.23%,显示出甘蔗块固定化法酵母发酵优于海藻酸钙包埋法固定化酵母。此外,甘蔗汁培养基与废糖蜜培养基对总体发酵效果的影响非常接近,但综合考虑甘蔗汁与废糖蜜的成本,废糖蜜是工业发酵生产乙醇用培养基的更优选择。     

以多孔性载体为支持体的酵母细胞固定化方法的研究(摘要)——柱式糖蜜原料的酒精快速连续发酵

一前言固定化微生物细胞技术是一项国内急待发展的新技术,引起了人们极大的关注。目前,采用的固定化方法主要有包埋法、吸附法和交联法等。其中研究较为广泛的是包埋法,特别是利用海藻酸钙凝胶和角叉菜作为包埋剂。因为这种方法简单易行,且凝胶无毒性。但是,仅用包埋法制得的固定化颗粒机械强度有限,尤其是角叉菜凝胶价格偏高,限制了它在工业生产中的应用。有些研究者研究了利用各种材料的吸附特性固定微生物细胞。但仅用吸附法固定微生物细胞,吸咐菌体数量不多,发酵过程中细胞泄漏较大,限制了吸咐法在工业生产中的应用。     

固定化根霉细胞产生糖化酶的研究

选取精化用菌Rh delemer3．5进行细胞固定化,经增殖后于液体培养基中进行好气性发酵,产生糖化酶实验结果表明,海藻酸钙是适宜的固定化载体,相同条件下固定化细胞的产酶能力较游离细胞高60~80%,并可连续使用300小时以上。电子显微镜观察表明:根霉在海藻酸钙凝胶内生长良好,保持较长的稳定期,处于不断产酶状态。     

固定化混菌发酵制备乳酸的研究

本文研究了以淀粉水解液为原料,用海藻酸钙包埋乳酸杆菌及乳脂链球菌混菌发酵制备乳酸的条件及性质。结果表朗:发酵72小时混菌发酵的乳酸浓度,分别比单菌乳酸杆菌及乳脂链球菌提高17.81、11.0%;混菌发酵的最佳温度为40℃;单独固定乳酸杆菌和乳脂链球菌后,再混合的发酵速度,比二种乳酸菌混合再用海藻酸钙固定的发酵速度要高13.1%,固定化混菌比游离细胞制备乳酸的产酸率高37.7%。     

包埋法固定肠膜明串珠菌材料的研究

包埋法是固定化技术中应用最为广泛的一种方法,其中的凝胶包埋法以其原料简单、容易操作的特点被广泛采用。在对包埋法固定肠膜明串珠菌的材料选择上,选取了四种海藻酸盐凝胶——海藻酸钙凝胶、海藻酸铝凝胶、海藻酸锰凝胶和经戊二醛处理的海藻酸钙凝胶,设计实验对四种材料的机械性能、吸收性能、释放性能和产糖量进行对比,结果表明:四种材料的机械强度大小排序为:海藻酸铝﹥海藻酸锰﹥戊二醛处理海藻酸钙﹥海藻酸钙;吸收性能大小排序为:戊二醛处理海藻酸钙﹥海藻酸锰﹥海藻酸钙﹥海藻酸铝;释放性能大小为:海藻酸锰﹥海藻酸钙﹥海藻酸铝﹥戊二醛处理海藻酸钙;产量高低排序为:海藻酸钙﹥海藻酸锰﹥海藻酸铝﹥戊二醛处理海藻酸钙。通过对比,综合考虑多方面因素,最终选取海藻酸钙凝胶作为固定化肠膜明串珠菌的材料。     

若干种有机试剂对固定化酸性蛋白酶活性影响的初步研究

用海藻酸钙凝胶将黑曲霉产的酸性蛋白酶固定化,并研究了其若干性质。用4%的海藻酸钠与0.5%CaCl2制备的海藻酸钙凝胶将酶固定后,该固定化酶的活性回收率为33.33%。随浓度的增加,乙醇、丙三醇或SDS对这两个酶的抑制作用逐渐增强,而0～1.5mol/L盐酸胍、0～4mmol/L尿素却分别激活这两个酶。总之,固定化酸性蛋白酶对丙三醇浓度变化的敏感性较游离酶要大些,但对其它几种有机试剂浓度的变化的敏感性不及游离酶。     

固定化光合菌群利用秸秆水解液发酵产氢特性研究

利用玉米秸秆水解液为基质,采用海藻酸钠包埋方法固定光合菌群,进行固定化光合细菌发酵产氢研究,考察了菌液包埋量、颗粒粒径、海藻酸钠浓度、CaCl2浓度和光照强度的影响。结果表明,当菌液包埋量为4mL,颗粒粒径为2.5mm,海藻酸钠浓度为1.5%,CaCl2浓度为10%,光照强度为7000lux,效果较好,培养72h后,总产氢量最高可达491mL H2/L-培养基,是相似条件下游离态光合菌群发酵产氢的1.2倍,为固定化光合细菌利用玉米秸秆发酵产氢研究提供参考。     

海藻酸钙固定水生假丝酵母生产耐酸性α-淀粉酶

介绍了以海藻酸钙为载体,对水生假丝酵母进行包埋固定处理,并利用这种固定化细胞生产酸性α-淀粉酶的方法。实验表征了固定化过程的工艺条件对海藻酸钙固定化水生假丝酵母细胞的结构、机械强度和产酶性能的影响,确定了最优的工艺条件为：在30％条件下,将2．8％海藻酸钠、0．6％的菌体的混合液体,通过注射器缓慢注入4％CACl2溶液中固定4h。这种固定化细胞的产酶能力为70．24U／mL,比游离细胞高9．45倍。     

若干种有机试剂对固定化酸性蛋白酶活性影响的初步研究

用海藻酸钙凝胶将黑曲霉产的酸性蛋白酶固定化,并研究了其若干性质。用4%的海藻酸钠与0.5%CaCl2制备的海藻酸钙凝胶将酶固定后,该固定化酶的活性回收率为33.33%。随浓度的增加,乙醇、丙三醇或SDS对这两个酶的抑制作用逐渐增强,而0～1.5mol/L盐酸胍、0～4mmol/L尿素却分别激活这两个酶。总之,固定化酸性蛋白酶对丙三醇浓度变化的敏感性较游离酶要大些,但对其它几种有机试剂浓度的变化的敏感性不及游离酶。      

固定化酵母发酵蔗汁产酒精载体选择及发酵工艺研究

以海藻酸钙和甘蔗渣为载体固定酵母细胞,进行蔗汁酒精发酵。比较了两种方法和载体性能,并优化发酵工艺。结果表明,海藻酸钙包埋法固定化酵母发酵优于蔗渣吸附法,其最佳工艺条件为：发酵温度33℃、pH值4.5、粒子填充率25%。最佳条件下的验证试验结果表明,酒精得率最高可达93.21%,发酵时间22 h。     

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.     

Detection of adulteration of locust bean gum with guar gum by capillary electrophoresis and polarized light microscopy

Capillary electrophoresis (CE) and polarized light microscopy (PLM) were utilized in the detection of the adulteration of locust bean gum with guar gum. For CE analyses, standards of locust bean and guar gums were extracted with 30% CH₃CN, removing the residual proteins from the gum matrix. A 8.75 mM NaH₂PO₄-20.6 mM Na₂B₄O₇ buffer, pH 9, was used to separate these proteins and to identify marker proteins that were present in the guar gum. These markers did not co-migrate with components in the extracts of mechanically processed locust bean gum, and are used as indicators of adulteration. Using PLM with toluidine blue and iodine staining techniques, unadulterated locust bean gum samples were distinguished from mixed samples through the differential staining of components in locust bean versus guar and tara gums. These experiments in the use of CE and PLM provide orthogonal and complementary methods for the verification of 'true' positives and the elimination of 'false' positives.