乳酸杆菌表层蛋白及应用研究

在一些古细菌和真细菌中,表层蛋白是细胞膜最外层的结构。尽管所有表层蛋白具有相同的氨基酸成分,但是与其他细菌表层蛋白相比,乳酸杆菌表层蛋白具有其独有的特性:小分子量,高等电点,为碱性蛋白。一些乳酸杆菌具有多个表层蛋白基因。国外学者对表层蛋白作为功能分子共价吸附固定的基质、表面展示载体和分子筛等方面的应用进行了深入研究,展示了巨大的发展前景。     

乳酸杆菌S-层蛋白的结构及免疫调控功能研究进展

本文综述了乳酸杆菌S-层蛋白的结构及功能,包括S-层蛋白对胆盐及消化酶的耐受能力、参与乳酸杆菌对宿主的黏附作用、抑制病原菌对宿主细胞的黏附及侵入作用。并且详细阐述了S-层蛋白对细胞信号通路的调节功能,证明S-层蛋白对于乳酸杆菌发挥免疫调节功能具有重要的作用。     

双纤维素酶基因在乳酸杆菌中的融合分泌表达

为提高纤维素的降解效率,将两种不同的纤维素酶基因在乳酸杆菌中融合表达,实现双纤维素酶在乳酸杆菌中的高效表达。根据两纤维素酶的基因序列设计两对引物,并在两基因间引入一段连接肽。通过聚合酶链式反应（polymerase chain reaction,PCR）分别扩增得到两纤维素酶基因CelL15和CelL73,将其融合后连接到乳酸杆菌分泌性表达载体pMJ67中,构建重组表达质粒pMJ-CelL15-CelL73,电转化入乳酸杆菌Lactobacillus casei,利用红霉素MRS平板筛选阳性克隆,通过PCR验证获得了分泌表达双纤维素酶的重组乳酸杆菌。电泳实验结果表明重组乳酸杆菌成功表达了1 个约为83 kD的融合蛋白。平板酶活力检测发现重组乳酸杆菌能明显降解底物中的羧甲基纤维素钠,培养液上清中纤维素酶酶活力可达1.25 U/mL。     

嗜酸乳杆菌S-层蛋白的提取和鉴定

采用高浓度溶剂法(氯化锂/盐酸胍)及溶菌酶结合氯化锂法提取3株乳酸杆菌的表层粗蛋白,通过SDSPAGE比较不同方法及菌株的蛋白提取效果。对嗜酸乳杆菌CGMCC 1.1878表层粗蛋白进行凝胶过滤层析纯化后,采用MALDI-TOF-TOF对纯化的蛋白进行二级质谱鉴定,用扫描电镜观察蛋白表面形态。结果表明:高浓度溶剂法提取的蛋白条带多集中在40~60 ku,其中,氯化锂溶剂所提蛋白特征条带明显,便于纯化及分析。根据MASCOT软件搜索及NCBInr数据库比对,成功鉴定出该纯化蛋白为嗜酸乳杆菌S层蛋白,分子质量为46 ku。     

乳杆菌表层蛋白对菌株表面特性和益生特性的影响

为评估乳杆菌表层蛋白对菌株特性的影响,该研究通过序列比对筛选出含slp基因的乳杆菌,之后用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）对其中部分菌的slp基因表达情况进行鉴定,并测定了表层蛋白去除前后菌体生长的吸光度值、自聚集率、自成膜量、与致病菌共聚集率等特性。结果表明,4株嗜酸乳杆菌、30株卷曲乳杆菌、3株瑞士乳杆菌、30株鼠李糖乳杆菌都含有slp基因,经过SDS-PAGE鉴定了四种菌的部分菌株均表达表层蛋白,且其表层蛋白与菌株的特性密切相关。比如,在生长方面,瑞士乳杆菌去除表层蛋白前后生长能力差异很大,但氯化锂溶液和蛋白酶K两种溶液处理的吸光度值差距较小,差值仅在0.2以内;在与致病菌共聚集方面,大部分菌株在不同处理过程中没有较大差异,有趣的是,本身自聚能力弱的鼠李糖乳杆菌3-1表现出来的与致病菌极强的共聚能力,这株菌的在口腔方面的防龋潜力值得进一步探究。该研究丰富了人们对乳杆菌表层蛋白的了解,为深入探究表层蛋白的功能和应用奠定理论基础。     

啤酒酵母絮凝机理研究进展

啤酒酵母絮凝机理的假说有絮凝共生假说、类外源凝集素假说、类外源絮凝素假说等。啤酒酵母絮凝表型可分为FLO1型和NewFLO型；对啤酒酵母絮凝基因的研究有结构基因——见O基因家族、调节基因及其他相关絮凝基因。对啤酒酵母絮凝性状的改良研究可应用于调控啤酒酵母絮凝性状，利于啤酒生产；利用酵母絮凝性状构建絮凝选择栽体；利用絮凝素蛋白构建酵母细胞表层展示体系；利用酵母絮凝蛋白对细菌的吸附，应用于医疗行业。     

乳清蛋白和豌豆蛋白对抗生素致肠道菌群紊乱小鼠的调节作用

目的：探究乳清蛋白和豌豆蛋白对肠道菌群紊乱小鼠的调节作用。方法：向小鼠灌胃盐酸林可霉素建立肠道菌群紊乱模型,对模型小鼠进行蛋白或蛋白与益生菌联合干预,干预结束后检测小鼠盲肠内容物中肠球菌、大肠杆菌、乳酸杆菌、双歧杆菌含量,评价小鼠肠道微生物的定植抗力。收集各组小鼠新鲜粪便提取细菌基因组DNA进行16S rDNA测序,评价不同样品对肠道菌群的影响。结果：相比于模型组,各处理组不同程度地提高了小鼠肠道菌群定植抗力以及物种丰富度和多样性,改变了菌群组成结构,减少了致病菌数量,促进了有益菌或中性菌增殖,调节了菌群功能基因组成,各处理组小鼠的肠道菌群物种组成和功能基因组成都趋向于空白组水平。结论：乳清蛋白、豌豆蛋白以及豌豆适度水解蛋白肽均可调节肠道菌群结构,改善由抗生素导致的肠道菌群紊乱状况。     

一株乳酸杆菌的基因工程筛选标记研究

研究氯霉素、氨苄青霉素、卡那霉素三种抗生素和D-木糖、D-甘露糖两种糖类对乳酸杆菌生长的抑制效果,探讨相应标记基因作为乳酸杆菌RL01基因工程筛选标记的可行性.结果表明:(1)低浓度(5 mg/L)的氯霉素和氨苄青霉素能显著抑制和杀灭乳酸杆菌,卡那霉素在5mg/L-400mg/L浓度范围内不能抑制乳酸杆菌的生长.氯霉素抗性基因和氨苄青霉素抗性基因(Ampr)适合作为菌株RL01的筛选标记基因,卡那霉素抗性基因(Kan)不适合.(2)乳酸杆菌RL01能够利用D-甘露糖作为碳源,磷酸甘露糖异构酶基因(pmi)不适合作为乳酸杆菌的筛选标记.D-木糖作为碳源时,乳酸杆菌的生长受到明显抑制,木糖异构酶基因(xyLA)有可能作为该菌株的食品级筛选标记.     

乳酸菌表层蛋白的分离及其结构和性质

对自主拥有的多株乳酸菌进行了表层蛋白的分离和鉴定,并对其结构和性质进行了研究。采用LiCl溶液进行提取,经SDS-PAGE检测,确定嗜酸乳杆菌fb116、嗜酸乳杆菌fb115和瑞士乳杆菌fb213携带表层蛋白。采用差示扫描量热仪(DSC)测定,其变性温度分别为63.67℃,61.98℃和59.78℃。它们的氨基酸组成大致相同,疏水氨基酸含量高达45%,酸性氨基酸含量在21%左右,远高于碱性氨基酸。圆二色谱法(CD)分析显示,其二级结构相似,α-螺旋和β-折叠约占34%和12%。去除表层蛋白之后,3株菌株的自动聚集能力和表面疏水性出现下降,这提示表层蛋白的存在有助于乳酸菌黏附性能的发挥。     

不同pH对嗜酸乳杆菌分选酶相关基因表达及菌体黏附能力的影响

为探究嗜酸乳杆菌在小肠中黏附调控机制,嗜酸乳杆菌黏附与细胞壁分选酶及其相关蛋白的基因表达之间的关系。实验构建体外模型研究了不同p H培养条件下嗜酸乳杆菌的黏附能力、测定了分选酶基因和分选酶相关蛋白基因相对表达差异。实验结果表明:在p H5.5~7.5培养条件下,随着p H升高嗜酸乳杆菌菌体黏附性显著增加,srt基因及其相关蛋白的基因表达量显著上调。研究结果为p H对嗜酸乳杆菌的黏附效应的影响机制提供了相关理论依据。     

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.     

Review of techniques to manufacture micro-hydrogel particles for the food industry and their applications

Microgels are ‘soft’ microscopic cross-linked polymeric particles that are being increasingly exploited in a variety of industries for rheology control, encapsulation and targeted delivery. They are valued because of the ability to tune their functionality to address specific applications in oil recovery, coatings, drug delivery, cosmetics, personal care and foods. Food microgels are typically biopolymer hydrogels in the form of microspheres, nanospheres (also called nanogels), spheroids and fibres. The utilisation of engineered microgels in foods has so far been limited, despite their great potential to address several needs in the food industry, including: satiety control, encapsulation of phytonutrients and prebiotics, texture control for healthier food formulations (e.g. reduced fat products), and targeting delivery to specific areas in the digestive tract. We review the scientific and patent literature on the utilisation and manufacturing methods for producing microgels with an emphasis on micro-hydrogels for food applications.     

12—A CRITIQUE OF SOME HYPOTHESES RELATING TO THE HETEROGENEITY OF THE HIGH-SULPHUR PROTEINS OF WOOL

Joubert and Burns prepared a large number of fractions from the high-sulphur proteins of wool and estimated their molecular weights and amino-acid compositions. Their data have been re-examined in order to look for statistically significant interrelations between amino acids and between the proportion of various amino acids and molecular weight. Statistical analysis of the data is also used to examine the credibility of some hypotheses concerning the mechanism of keratin biosynthesis and to provide further evidence for the existence of families of proteins within the high-sulphur fractions of wool.     

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 Latest Data about Development of Chinese Printing Industry in 2013

In the 2014 China（Shanghai）International Printing Week,Director Wang Yanbin released the latest data about development of Chinese printing industry in 2013.According to statistics,in 2013,the total output value of Chinese printing industry exceeded 1trillion Yuan for the first time,reaching 1.03985 trillion Yuan.There were 105,000 printing enterprises in China,employees were 3.415 million.The total asset was 1.06247 trillion Yuan;     

The State Council Issued "Directory of Government Approved Investment Projects(2013 Edition)"

正On December 2nd,2013,the State Council issued the notification of"Directory of Government Approved Investment Projects(2013 Edition)"(hereafter referred to as"notification").It is pointed out in the"notification"that in order to further deepen reforms in investment systems and administrative examination and approval systems,simplify administrative procedures and delegate powers to lower levels,earnestly     

China textile machinery: taking off in progress

正Among the 1600 exhibitors who take apart in the ITMA ASIA+CITME2014 2/3 are Chinese manufactures.If the numerous figures failed to attract your attention,the increase of quality should draw your focus.To adopt the demand of developing textile machine market,domestic textile machinery enterprises now follow the slogan of"technology drives development"to enhance product competitiveness.Our domestic sellers will showcase product ranging from spinning,weaving,dyeing and printing,     

Top Ten News of China's Paper Industry 2013

On December 24th, 2013, the meeting on the selection of top 10 news of China＇s paper industry 2013 sponsored by 〈China Paper Newsletters〉 was held in Beijing. The yearly selection of the top l0 news, which began in 2000, has become a brand activity widely recognized in the industry thanks to the support from the authorities at all levels and public participation.