米根霉乙醇脱氢酶粗酶液的特性研究

米根霉细胞中乙醇脱氢酶(ADH)催化丙酮酸向乙醇支路的转化,导致丙酮酸向乳酸转化通量减少,降低了乳酸转化率。本文初步从米根霉菌丝体中提取制备ADH粗酶液,并研究其酶学特性,结果表明,ADH粗酶液体系反应的最适温度为25℃,温度高于30℃将降低ADH活力。ADH催化体系pH值对其活力有很大影响,最适pH值在7.5左右,高于或低于此值,反应速度均很快下降。在反应体系中添加0.1μmol的EDTA、Mg2+、Ca2+或Zn2+,对该酶都有一定的抑制作用。ADH以乙醛为底物的米氏常数Km为6.90×10-4mol/L。     

L-乳酸米根霉发酵体系LDH活力及代谢调控研究

乳酸脱氢酶(LDH)是米根霉代谢生产L-乳酸过程的关键酶，研究其在发酵过程中的活力变化，从酶水平分析发酵条件对L-乳酸发酵的影响，对米根霉发酵生产L-乳酸的人工代谢调节、菌种选育具有重要意义。本文研究了摇瓶条件下的米根霉AS3．1208发酵体系中乳酸脱氢酶的活力调控条件及与L-乳酸即时产率的关系，结果表明，发酵体系中L-乳酸产率与LDH活力在36～40h时最高。葡萄糖作为C源的L-乳酸产率与LDH活力比甘薯淀粉高。与牛肉膏和蛋白胨相比，硫酸铵是米根霉代谢的最佳N源，0．40％的硫酸铵具有较高的乳酸产率与LDH活力。发酵培养基中添加CaCO3与否，对乳酸产率与LDH活力有极大影响。以甘薯淀粉为碳源，在250ml三角瓶中的装液量为100ml，发酵36～40h时的L-乳酸即时产率最大，此时LDH活力也最高。     

米根霉不同菌丝体形态对重复间歇发酵生产L-乳酸的影响

研究米根霉在3L 发酵罐重复间歇发酵过程中,菌体形态对发酵强度的影响。结果表明：絮状米根霉首批发酵产L- 乳酸为105.8g/L,葡萄糖转化率88.12%,球状米根霉产L- 乳酸105.0g/L,葡萄糖转化率87.50%;在重复间歇发酵过程中,球状米根霉前6 批产L- 乳酸均保持在80.00g/L 以上,第7 批产L- 乳酸78.60g/L,葡萄糖转化率均高于87.33%,产酸效率最高可达到4.26g/(L·h),而絮状米根霉前4 批产L- 乳酸可保持在80.00g/L 以上,第5 批产L- 乳酸78.30g/L,第6 批产L- 乳酸77.40g/L,第7 批产L- 乳酸70.20g/L,产酸效率最高可达4.07g/(L·h)。研究数据显示,球状米根霉更适于重复间歇发酵生产L- 乳酸。     

不同中和剂对米根霉发酵产L- 乳酸的影响

在米根霉发酵产L- 乳酸过程中,采用CaCO3 作为中和剂会造成下游分离过程中膜堵塞和环保压力,因此以NH3·H2O 和NaOH 替代CaCO3 作中和剂,对米根霉发酵产L- 乳酸的工艺条件和发酵动力学进行研究。结果表明：添加CaCO3 后L- 乳酸产量平均提高7.3 倍;NaOH、NH3·H2O 作为中和剂的最佳浓度及质量分数分别为10mol/L、25%,以该条件进行发酵72h 得菌丝体小球直径分别为0.2～1.2mm 和1.2～2.2mm,残糖含量分别为2.58g/L 和1.37g/L,L- 乳酸产量分别为74.34g/L 和80.61g/L。     

利用纤维废弃物生产L-乳酸的研究

为了使对环境造成污染的纤维废弃物得到资源化利用,采用纤维素酶对纤维废料进行酶解,并用米根霉发酵生产L-乳酸.研究结果表明,0.3 mol/L稀磷酸对纤维废弃物进行预处理后,纤维素酶酶解60h,取糖化液进行米根霉发酵,可得到较佳转化率;在固定摇床转速为120r/min、种龄12 h的条件下,米根霉发酵生产L-乳酸的最佳条件为:装液量(250 mL瓶)50mL,接种量8%;经稀磷酸预处理纤维废料分别糖化发酵时,糖对L-乳酸转化率高于未经稀磷酸预处理的,而在同时糖化发酵过程中,经稀磷酸预处理纤维废料发酵效果不明显.     

以玉米粉为原料L-乳酸高产菌株的选育和产酸条件的研究

以玉米粉为原料,米根霉为初始菌株,采用超声波-紫外线进行复合诱变,选育出一株发酵玉米粉产L-乳酸的米根霉菌株NF12,其产酸量较初始菌株提高了21.61g/L。确定了10L罐发酵玉米粉产L-乳酸的最适发酵条件,结果表明:70%装填量,5%接种量,30℃,300r/min,通气流量0.6L/(L·min),溶氧90%,在此条件下进行发酵,L-乳酸产量为83.15g/L。     

米根霉L-乳酸发酵动力学

通过正交试验研究米根霉AS3.819利用葡萄糖发酵生产L-乳酸时,发酵培养基中葡萄糖、(NH4)2SO4、KH2PO4、ZnSO4·7H2O、MgSO4对发酵的影响.确定的最佳发酵培养基组成:葡萄糖80 g/L、(NH4)2SO4 2 g/L、KH2PO4 0.3 g/L、ZnSO4·7H2O 0.05 g/L、MgSO40.3 g/L.在此培养基组中平均发酵产L-乳酸61.5g/L,对葡萄糖的平均转化率为76.9%.初步建立米根霉AS3.819利用葡萄糖发酵生产L-乳酸的动力学模型,并通过发酵动力学试验获得到模型参数,对培养基中初始葡萄糖质量浓度分别为72、74g/L的发酵过程进行预报.结果表明,建立的动力学模型能较好地描述米根霉发酵生产L-乳酸的过程:L-乳酸的生成机制是以生长机制为主的混合动力学机制.     

米根霉发酵甘薯淀粉制备L-乳酸研究

以米根霉AS3.819的诱变株为菌种,甘薯淀粉为碳源,在摇瓶发酵工艺的基础上,利用10L发酵罐对该菌株产L-乳酸进行研究,探索出10L罐最适发酵条件为:装液量40%,搅拌转速400～650r/min,通气流量0.5～0.6L/(L·min),溶氧≥88%,温度32℃,pH5.0～5.5,消泡剂添加量0.1%左右。罐发酵结果得到L-乳酸累积浓度为99.54g/L,对原淀粉的转化率达77%,最高生物量7.2g/L,发酵周期70h。     

无载体固定化米根霉半连续发酵产L－乳酸工艺研究?

为了选择米根霉半连续发酵产L-乳酸工艺参数,通过单因素试验和正交试验,对接种量、CaCO3添加时间、温度、装液量及转速进行了优化,并采用培养基重复发酵,建立米根霉半连续发酵工艺。其中摇瓶半连续发酵条件为：孢子接种量4%,种子接种量10%,发酵开始时添加CaCO3,装液量为20%～30%,0～36h时发酵温度28～30℃、36～72h时发酵温度32～34℃,转速200r/min。7L磁力搅拌发酵罐半连续发酵工艺条件为：搅拌转速为300r/min,通气量为1.25L/(L·min),温度为32℃。发酵罐重复发酵稳定,产L-乳酸最高达到86%。为米根霉半连续发酵产L-乳酸的工业化生产提供了研究基础。     

米根霉液体发酵L-乳酸动力学模型的构建

由于研究生产L-乳酸代替D-乳酸和DL-乳酸已成为一种趋势,为构建米根霉液体发酵L-乳酸动力学模型,对米根霉发酵生产L-乳酸进行了初步研究。在米根霉分批发酵过程中,测定菌体生物量、还原糖和乳酸含量,经处理后得到菌体生长、乳酸生成和基质消耗的动力学模型及参数。对比实验数据与模型表明,两者能较好拟合,基本反映米根霉发酵L-乳酸动力学特征。     

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