S.griseoverticillatum合成谷氨酰胺转胺酶发酵条件的研究

本文以S.griseoverticillatu ZY13作为生产菌株,利用液体深层发酵技术生产谷氨酰胺转胺酶.结果表明在500 mL摇瓶中,菌株ZY13的最佳种龄48 h、最佳培养温度28～30℃、培养时间64 h、pH值6.5～7.0、接种量5%～10%、装液量100 mL.培养基最佳组合为淀粉30 g/L、蛋白胨35 g/L和酵母膏3 g/L.添加硝酸钠有利于MTG的积累,酶活比对照提高了31%.在7.0 L台式发酵罐中发酵,适宜的初始pH值7.0,温度30℃,通气量2.0 L/min,搅拌转速150 r/min.MTG分批发酵与摇瓶相比较,发酵周期缩短了8小时,菌体细胞干重、酶活和生产强度分别增加了16%、27%和46%.     

热带假丝酵母发酵法生产木糖醇的研究

目的利用热带假丝酵母研究发酵木糖生产木糖醇的发酵条件。方法采用摇瓶发酵对发酵生产条件,如培养基中初始木糖浓度、接种量和通气量、氮源、pH等进行优化,通过测定发酵液中木糖的残留量、木糖醇的转化率来确定适合的发酵工艺。结果通过实验得到最佳培养基条件为:初始木糖50g/L,蛋白胨5g/L,酵母粉10g/L,硫酸镁0.5g/L、磷酸二氢钾5g/L,硫酸铵1g/L;最佳发酵条件为:pH 6.0,摇瓶发酵装液量50mL/250mL,转速200 r/min,发酵温度30℃,发酵时间28h。结论优化了木糖醇的发酵工艺。     

褶皱假丝酵母产脂肪酶条件及酶学性质研究

对一株来源于海洋有产脂肪酶能力的褶皱假丝酵母产酶条件进行研究,探讨了碳源、氮源、pH、培养温度对该菌产脂肪酶的影响。结果显示:在摇瓶培养条件下,其最适产酶条件为:蔗糖5 g/L,橄榄油5 g/L,MgSO4·7H2O1 g/L,K2HPO41 g/L,(NH4)2SO410 g/L,起始pH为7.0,接种量10%,在30℃、200 r/min下培养36 h,产酶能力达到4 351.6 U/mL。该菌所产脂肪酶的最适反应pH为7.0,最适反应温度为37℃,Ca2+、Mg2+对酶活有一定的促进作用。     

粗状假丝酵母产脂肪酶发酵条件的优化

利用粗状假丝酵母发酵生产脂肪酶,通过对粗状假丝酵母胞外脂肪酶发酵过程的培养基和发酵培养条件的优化,得出产脂肪酶的最佳条件:碳源为聚乙烯醇乳化的橄榄油和葡萄糖,氮源为蛋白胨和尿素,酵母浸出液4.5g/L,MgSO4.7H2O0.4g/L,K2HPO43.5g/L;反应温度30℃,培养基初始pH7.0,接种量为10%,摇床转速180r/min,培养24h。在此发酵条件下,发酵液的最高酶活达到12U/mL。     

链霉菌生产谷氨酰胺转胺酶的发酵工艺条件研究

以本实验室从土壤分离并经诱变筛选得到的链霉菌 Streptomyes sp.WZFF.W—12.var MN-35为出发菌株, 首先在摇瓶条件下,对微生物谷氨酰胺转胺酶(MTG)发 酵生产过程中的主要培养基组成、培养条件及各种蛋白 酶抑制剂对菌体生长和产酶能力的影响进行了研究。结 果表明,发酵生产MTG的合适碳氮源分别为可溶性淀 粉与葡萄糖和多价胨,其最佳碳氮比(C/N)为5:5,适宜 的接种龄、接种量、初始pH、培养温度、搅拌速度等工艺 条件分别为24h、7％～10％、pH6.5～7.0、30℃和200r/min, MTG酶活最高可达1.63U/mL。当在优化培养基中进一 步加入一种蛋白酶抑制剂后,酶活又提高了19.0％。在这 些最佳工艺条件下采用简易的小型生化反应器培养该链 霉菌株,酶活稳定在2.0U/mL以上。     

粗状假丝酵母(Candida valida T2)生产脂肪酶的发酵条件

对粗状假丝酵母产生脂肪酶的培养条件进行了研究。结果表明,该菌株产脂肪酶的适宜培养基组成为:桐油15mL/L,黄豆粉30g/L,糊精10g/L,硝酸铵10g/L,MgSO4·7H2O1g/L,K2HPO42g/L,Tween800.5g/L;最佳培养为温度30℃、发酵液起始pH6,摇瓶发酵脂肪酶活力达到1467U/mL。     

大豆糖蜜高产单细胞蛋白菌株的筛选及其生长条件

以大豆糖蜜为底物,通过平板初筛和三角瓶摇瓶发酵复筛,从8株单细胞蛋白生产常用的酵母菌中筛选出在10%大豆糖蜜中生物量和总蛋白产量最高的热带假丝酵母CGMCC2.587,其细胞生物量为8.4125g/L,总蛋白产量为4.4696g/L。通过单因素实验确定了菌株生长的最佳培养基为5%麦芽汁培养基;培养条件为初始pH5.0、装液量50mL/250mL、转速160r/min、温度30℃。     

链霉菌TCCC11564葡萄糖异构酶发酵条件优化及酶学性质的研究

通过单因素及正交试验设计确定链霉茵TCCC11564摇瓶发酵产葡萄糖异构酶的最佳发酵条件为:麦芽糖1.0%,蛋白胨0.5%,硫酸镁0.06%,磷酸氢二钾0.05%,氯化钠0.05%,30℃、180 r/min摇瓶发酵48 h,在此条件下得到的发酵液酶活最高达到428.8U/mL,比优化前的116.08U/mL提高了3.69倍.酶学性质研究结果表明,链霉茵TCCC11564葡萄糖异构酶最适反应温度为70℃～75℃,90℃保温120 min后酶活几乎完全丧失.pH为7.5～8.5之间具有较好的稳定性,pH在7.5以下时,稳定性下降,在pH为6.5时酶活损失50%以上,反应的最适pH是8.0.     

响应面法优化灰绿青霉Penicillium glaucum NS16产酶条件

采用响应面法对灰绿青霉Penicillium glaucum NS16生产纤维素酶的发酵条件进行了优化,通过Plackett-Burman实验方法研究有关碳源、氮源、无机盐、发酵时间、摇床转速等18个发酵因子对菌株发酵产纤维素酶活力的影响.结果显示,影响产酶的显著因子是麸皮、CMC的含量和发酵时间.根据实验结果和经验方法对显著影响因子的取值范围进行预估,并采用Box-Behnken设计实验进行优化,然后应用响应面模拟预测和摇瓶发酵实验验证,结果表明,优化发酵条件为培养基中麸皮6.0 g/L,CMC 7.0 g/L,发酵时间96 h,摇瓶发酵液中CMC酶活均接近309 IU/mL,优化预测值和实验验证值拟合度达到99%,比初始培养基和发酵条件下菌株产CMC酶活94.51 IU/mL提高了227%.     

重组蔗糖异构酶在短短芽孢杆菌中的表达及发酵优化

对重组菌株Brevibacillus choshinensis/pNCMO2-SI摇瓶发酵产蔗糖异构酶进行研究,进一步探讨了3 L发酵罐不同发酵条件对菌体生长及产酶的影响。结果表明,摇瓶发酵后胞外酶活为50 U/mL,最优3 L发酵罐培养条件为:初始碳源为葡萄糖质量浓度10 g/L,初始氮源为多聚蛋白胨、牛肉浸膏质量浓度各15 g/L,发酵温度30℃,溶氧30%,在此条件下得到的最高酶活为275 U/mL。为了探索启动子对蔗糖异构酶表达的影响,分别选取来源于枯草芽孢杆菌的启动子Papr-E,Pnpr-E,Pamy以及来源于巨大芽孢杆菌的启动子Pxyl进行研究。结果表明,使用启动子Papr-E的表达量最高。进一步优化摇瓶发酵条件,重组菌株BCpNapr-SI摇瓶发酵的胞外上清酶活为137 U/mL,在此条件下进行3 L发酵罐发酵,最终发酵上清胞外酶活为485.5 U/mL,是未优化启动子的1.76倍。     

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.     

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.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

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.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.     

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