酒用酸性脲酶的纯化及其N端序列的测定

采用乙醇分级沉淀、Superdex200凝胶过滤、Mono Q离子交换对Enterobactria sp R-SYB082产酒用酸性脲酶进行了纯化.SDS-PAGE电泳结果表明,该酶已达到电泳纯,纯化倍数为21.1,酶活回收42%.Superdex200凝胶过滤测定其全酶相对分子质量约为430 000,SDS-PAGE电泳测定其亚基相对分子质量约为72 000,表明该酶为同源六聚体,并利用Edman降解法测定了蛋白质N端序列的8个氨基酸残基序列:S-F-K-M-D-R-K-Q.酶反应的最适pH为4.5,最适温度为35℃.以尿素为底物时,该酶表现Km及Vmax分别为19.5μmol/L和0.87μmol/min.Na 、Mn2 对酶活有一定的激活作用,Ca2 、Zn2 对酶活有一定的抑制作用,酒石酸、琥珀酸对酶活有一定的激活作用,草酸、乙酸对酶活有一定的抑制作用.     

胞外单宁酶纯化及酶学性质的研究

采用黑曲霉B0201固态生料发酵生产胞外单宁酶,经过硫酸铵分级沉淀、DEAE-纤维素层析、葡聚糖G-150凝胶柱层析纯化,得到电泳纯的单宁酶,纯化倍数达到18.44。对该酶的性质研究表明:单宁酶的相对分子质量大小约为58800,该酶的最适反应温度是40℃,最适反应pH值是5.0;以PG为底物,米氏常数Km为1.08mmol/L,Vmax为104.1μmol/(L.min)。     

高活性大豆异黄酮糖苷酶的分离原料筛选、纯化及性质研究

通过对32种植物β-葡萄糖苷酶水解染料木苷的活性比较,发现鹰嘴豆β-葡萄糖苷酶具有4.19U/mg的大豆异黄酮糖苷水解酶活性.该酶经硫酸铵分级沉淀、DEAE-Cellulose-52离子交换、Sephadex G-100凝胶层析纯化,纯化了10.1倍,收率为7.2%;SDS-PAGE和Sephadex G-100凝胶层析结果表明,该酶的分子量为73.2kD,含两个亚基;该酶的最适反应温度为45℃;最适pH6.0;当以染料木苷和大豆苷为底物时该酶的米氏常数分别为11.0和19.0μg/ml.温度在30～45℃、pH值在4.5～6.5范围内该酶较稳定;Ag+、Hg2+和D-葡萄糖酸内酯对该酶有强烈抑制作用.该酶能水解染料木苷和大豆苷,但不能水解纤维二糖和α-乳糖.     

乳酸菌β-葡萄糖苷酶的分离纯化及特性研究

本文采用硫酸铵分级沉淀、DEAE-52离子交换层析、Sephadex G-100凝胶过滤方法分离纯化乳酸菌中β-葡萄糖苷酶.经SDS-PAGE测定其相对分子量约为60kD.该酶以对硝基苯酚-β-D-葡萄糖苷为底物时,最适pH值和最适温度分别为6.0和40℃.在45℃以下,pH值在4.5～7.0之间酶活力相对稳定.Hg^2＋和Ag^＋对该酶活力有明显的抑制作用.     

猪心肌苹果酸脱氢酶的制备及应用

设计并优化了从猪心中提取高纯度苹果酸脱氢酶的技术路线,采用组织破碎、二度硫酸铵盐析、DEAE Sepharose F.F.离子交换层析、Phenyl Sepharose 6 F.F.疏水层析及Sephadex G-75 Fine凝胶过滤等方法进行分离纯化,苹果酸脱氢酶比酶活达1 212.97 U/mg,纯化倍数达122.64倍,酶活力收率为53.64%.Sephadex G-75 Fine凝胶过滤和SDS-PAGE电泳结果显示纯化的苹果酸脱氢酶相对分子质量约为 69 000 ,含有2个亚基,每个亚基的相对分子质量约为 34 000 .以制备的苹果酸脱氢酶和谷草转氨酶配成双酶反应体系,对葡萄酒中L-苹果酸的含量进行了测定;通过标准样品和葡萄酒样品精密度及回收率(93.2%～104%)实验.     

嗜热芽孢杆菌HSO8耐热中性蛋白酶的分离纯化及部分特性研究

从高温土壤中分离出1株产耐热中性蛋白酶的嗜热芽孢杆菌,研究了该酶的分离纯化与生化特性.蛋白酶经硫酸铵沉淀、DEAE-Sepharose离子交换层析和Sephacryl S-100HR凝胶层析分离纯化后,纯化倍数提高4.25倍,产率5.1%;经SDS-PAGE电泳测得其分子质量为30.9 kDa.酶的最适温度与pH试验表明,其最适温度为65 ℃,最适pH为7.5,并在50 ℃时保持1 h以上的稳定.该蛋白酶活性受到EDTA的抑制,Zn2+能提高酶活性,该酶为金属蛋白酶.改性酪蛋白(Azocasein)、酪蛋白、牛血清白蛋白(BSA)等3种底物专一性试验表明,改性酪蛋白是其最适底物.     

小麦多酚氧化酶的分离纯化及酶学性质研究

为了减少多酚氧化酶(PPO)对产品所带来的负面影响,对从苏北红麦中提取的PPO粗提物进行分离纯化。经硫酸铵沉淀、DEAE阴离子交换层析和Superdex 200凝胶过滤层析,最终得到电泳纯化后只有一条条带的PPO,并对该纯化后的PPO进行酶学性质研究。试验结果为:纯化后PPO总酶活回收率为7.03%,纯化倍数22.35,比酶活为373.44 U/mg,电泳分析表明其相对分子质量约为30 000。测得其最适反应p H为6.5,最适反应温度为37℃;金属离子影响的研究表明,K~+、Na~+对其活性基本无影响,Ca~(2+)、Mg~(2+)、Mn~(2+)略有激活作用,Zn~(2+)、Cu2+激活作用较强;小麦PPO对邻苯二酚的K_m值为6.90 mmol/L,对焦性没食子酸(三酚类)、邻苯二酚(二酚类)底物亲和性较强,对单酚类(苯酚、愈创木酚)、二酚类(对苯二酚、间苯二酚)底物亲和性很低。     

裂褶菌产内切β-1,3-葡聚糖酶的特性研究

对裂褶茵所产内切β-1,3-葡聚糖酶进行有效分离纯化并用电泳法对其纯度进行鉴定,进而研究其酶学特性.结果表明:经过DEAE-Sephadex A-50离子交换层析和Sephadex G-75凝胶过滤分离纯化得到电泳纯分子量约为45 kD的内切β-1,3-葡聚糖酶,其最适pH为5.0,最适温度为45℃;Fe<'2+>、B...     

低温β-半乳糖苷酶分离纯化及酶学性质研究

对来自新疆天山冻土的Rahnella sp.R3所产的胞内低温β-半乳糖苷酶进行纯化,并对其酶学性质进行研究。采用硫酸铵分级沉淀、Phenyl Sepharose CL-4B疏水层析、Q Sepharose High Performance阴离子交换层析、Sephacryl S-200High Resolution凝胶过滤层析,得到电泳纯酶。酶的活性回收率为21.3%,纯化倍数为35.6,比酶活由1.28U/mg提高到45.54U/mg。SDS-PAGE电泳显示其表观分子量为57.3kDa。酶学性质研究表明,该酶最适反应温度为45℃,在15℃时的酶活为最高酶活的40%,4℃时的酶活为最高酶活的23%。该酶对热敏感,45℃保温45min酶活全部丧失。纯酶的最适pH为7.0,在pH 6.5~7.5时保持稳定。5 mmol/L Na+、Ca2+、Cu2+、Al 3+、Zn2+对酶活力有不同程度的抑制作用,其中Al 3+抑制作用最强,Na+、Ca2+抑制作用不明显。5 mmol/L Mg2+、K+对酶活力具有促进作用,其中Mg2+促进作用较强,使酶活提高到1.19倍。25℃以ONPG为底物的Vmax,Km值分别为7.19mol/(min·mL)、4.64mmol/L。     

K.paraultunense角蛋白酶的分离纯化及酶学性质研究

将角蛋白降解菌Keratinibaculum paraultunense(K.paraultunense)所产角蛋白酶的粗酶液,依次通过硫酸铵沉淀、DEAE-Sepharose-FF阴离子交换以及Superdex 75凝胶色谱层析等分离纯化,最终得到一种电泳纯的角蛋白酶。其纯化倍数为14.55,回收率为7.24%。SDS-PAGE分析结果表明该酶的相对分子质量约为29 KDa。酶学性质研究表明,该酶最适作用温度为80℃;最适pH为7.5,在pH 6.0～9.0范围内酶活力较为稳定;当以酪蛋白为底物时,该酶的动力学常数Km为4.37 mg·mL~(-1),Vm为14 556 U·(mg·min)~(-1),而当以羊毛角蛋白为底物时,该酶的动力学常数Km为15.66 mg·mL~(-1),Vm为2610 U·(mg·min)~(-1);Ca~(2+)对酶活有明显的促进作用,但苯基甲基磺酰氟(PMSF)对酶活有较强的抑制作用。     

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.     

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.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.     

Analysis for organic residues from aids to polymerization used to make plastics intended for food contact

Polymers intended for food contact use have been analysed for organic residues which could be attributed to a range of substances employed as polymerization aids (e.g. initiators and catalysts). A wide range of polymers was extracted with solvents and the extracts analysed by gas chromatography-mass spectrometry (GC-MS). The overwhelming majority of substances identified were not derived from aids to polymerization but were oligomers, additives and adventitious contaminants. However, a small number of substances were identified as initiator residues. These included tetramethylsuccinonitrile (TMSN) which was observed in two polymers and it derived from recombination of two azobisisobutyronitrile (AIBN) initiator radicals. Methyl benzoate, benzoic acid, biphenyl and phenyl benzoate were detected in one poly(methyl methacrylate) sample and in two polyvinylchlorides and they are thought to be derived from benzoyl peroxide initiator. TMSN was subsequently targeted for analysis of poly-(methyl methacrylate) plastics using proton nuclear magnetic resonance spectrometry (¹     

Tests of potential functional barriers for laminated multilayer food packages. Part II: Medium molecular weight permeants

Experiments were performed to characterize the kinetics of the permeation of different medium molecular weight model permeants: bisphenol A, warfarin and anthracene, from liquid paraffin, through a surrogate potential functional barrier (25 microns-thick orientated polypropylene--OPP) into the food simulants olive oil and 3% (w/v) acetic acid. The characterization of permeation kinetics generally observed the permeation models previously reported to explain the experimental permeation results obtained for a low molecular weight group of model permeants. In general, the model permeants exhibited behaviour consistent with their relative molecular weights with respect to (a) the time taken to attain steady-state permeation into the food simulant in which they were more soluble, (b) their subsequent steady-state permeation rates, and (c) their partition between liquid paraffin and the OPP membrane.     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis

This paper describes the first part of a project undertaken to develop mussel reference materials for Paralytic Shellfish Poisoning (PSP) toxins. Two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin (STX) and decarbamoyl-saxitoxin (dc-STX) in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the second part of the project: the certification exercise. In the first study, 18 laboratories were asked to measure STX and dc-STX in rehydrated lyophilized mussel material and to identify as many other PSP toxins as possible with a method of their choice. In the second interlaboratory study, 15 laboratories were additionally asked to determine quantitatively STX and dc-STX in rehydrated lyophilized mussel and in a saxitoxin-enriched mussel material. The first study revealed that three out of four postcolumn derivatization methods and one pre-column derivatization method sufficed in principle to determine STX and dc-STX. Most participants (13 of 18) obtained acceptable calibration curves and recoveries. Saxitoxin was hardly detected in the rehydrated lyophilized mussels and results obtained for dc-STX yielded a CV of 58% at a mass fraction of 1.86 mg/kg. Most participants (14 out of 18) identified gonyautoxin-5 (GTX-5) in a hydrolysed extract provided. The first study led to provisional criteria for linearity, recovery and separation. The second study revealed that 6 out of 15 laboratories were able to meet these criteria. Results obtained for dc-STX yielded a CV of 19% at a mass fraction of 3.49mg/kg. Results obtained for STX in the saxitoxin-enriched material yielded a CV of 19% at a mass fraction of 0.34mg/kg. Saxitoxin could not be detected in the PSP-positive material. Hydrolysis was useful to confirm the identity of GTX5 and provided indicative information about C1 and C2 toxins in the PSP-positive material. The methods used in the second interlaboratory study showed sufficiently consistent analysis results to undertake a certification exercise to assign certified values for STX and dc-STX in lyophilized mussel.     

The Ministry of Environmental Protection Issued "Feasible Technology Guidelines for Pollution Prevention and Control in Wood Pulping Process of the Paper Industry (Trial)" and Two Other Guiding Technical Documents

On December 27t＂, 2013, the Ministry of Environmenta Protection announced that, in order to implement ＂The Environmental Protection Law of the People＇ s Republic of China＂, improve the working system in environmenta protection technologies, and promote technologica advancement in pollution prevention, the Ministry of Environmental Protection sponsored the formulation of three guiding technical documents including ＂Feasible Technology Guidelines for Pollution Prevention and Contro n Wood Pulping Process of the Paper Industry （Trial）＂     

1~(st) Intelli-Tissue~ EcoEc Tissue Machine Supplied by PMP Group Successfully Put into Operation in China

正On April 29th,2014,Intelli-Tissue EcoEc tissue machine supplied by PMP Group successfully put into operation at Hebei Xuesong Paper Co.,Ltd.,this is the first such kind of paper machine of PMP Group in China.