异源表达酸土脂环酸芽孢杆菌DnaJ基因提高大肠杆菌胁迫抗性

构建重组质粒p ET28a-Dna J,转化大肠杆菌BL21(DE3),利用IPTG诱导重组大肠杆菌表达酸土脂环酸芽孢杆菌Dna J,对重组大肠杆菌和对照大肠杆菌分别进行热及酸、碱胁迫处理,研究酸土脂环酸芽孢杆菌Dna J基因异源表达对重组大肠杆菌胁迫抗性的影响。试验结果表明,经过热、酸胁迫后,重组大肠杆菌的存活率明显高于对照菌株,而在碱胁迫条件下,两种菌株的存活率相差不大,说明酸土脂环酸芽孢杆菌Dna J基因在大肠杆菌中异源表达能显著提高宿主菌对高温及酸胁迫的抗性,为发酵工业生产中构建高产抗逆工程菌株提供基因素材和理论依据。     

酸土脂环酸芽孢杆菌Fe-SOD基因克隆及生物信息学分析

酸土脂环酸芽孢杆菌具有嗜酸耐热的独特生理特性,从该属细菌中分离到的多种酶类都具有耐酸热稳定性,是筛选耐酸耐热酶的重要菌种资源。超氧化物歧化酶(SOD)由于具有重要的生理功能而广泛用于食品、药品及化妆品等行业。为了深入探讨酸土脂环酸芽孢杆菌SOD的分子生物学特性,本研究利用同源克隆、交错式热不对称PCR技术和生物信息学方法进行Fe-SOD基因克隆、测序及序列分析。结果表明,Fe-SOD基因(GenBank序列号:JN614998)ORF全长为606bp,编码202个氨基酸,其推测氨基酸序列与来源于酸热脂环酸芽孢杆菌DSM446的Fe-SOD(ACV58017.1)序列相似性最高,为78%。整个蛋白序列含有Fe/MnSODs家族的5个模体,SOD活性中心含有金属离子结合配基His27、His82、Asp164和His168,具有Fe/MnSODs家族典型的蛋白结构特征。酸土脂环酸芽孢杆菌Fe-SOD基因的克隆和生物信息学分析为进一步构建原核表达载体、获得生产耐酸热Fe-SOD的基因工程菌株奠定基础。     

橙汁主要营养成分及温度处理对脂环酸芽胞杆菌生长的影响

本文研究了橙汁主要营养成分和加工中温度处理等因素对两种引起已灭菌果汁腐败的主要病原微生物酸土脂环酸芽孢杆菌(A licyclobacillus acidoterrestris)和酸热脂环酸芽孢杆菌(A licyclobacillus acidocaldarius)生长的影响.结果表明,柠檬酸、蔗糖、矿质元素(钙、镁和钾元素)等橙汁中的主要营养成分在一定浓度范围内均可以促进两种脂环酸芽孢杆菌的生长.酸热脂环酸芽孢杆菌和酸土脂环酸芽孢杆菌在蔗糖浓度分别高于25％和20％时,生长受到抑制.当环境中钾浓度高于1000mg/L时,酸土脂环酸芽孢杆菌生长的生长受到抑制.在不同橙汁含量的饮料中,橙汁原汁最适合两种脂环酸芽孢杆菌的生长,而浓缩果汁中两种菌的生长量最少.温度处理实验表明,两种脂环酸芽孢杆菌分别经(-20、4、30、50、70、90℃)处理30min后,仍能保持良好的生长状态.当菌体经121℃处理30min时,生长几乎完全受到抑制.因此.橙汁饮料及橙汁原汁更容易感染酸土脂环酸芽孢杆菌和酸热脂环酸芽孢杆菌;通过巴氏杀菌很难彻底杀灭橙汁中的脂环酸芽孢杆菌,有必要寻求新型非热杀菌方法来控制橙汁中脂环酸芽孢杆菌.     

植物乳杆菌对脂环酸芽孢杆菌的抑菌机理研究

脂环酸芽孢杆菌是当前许多水果饮品中的致腐菌，其中酸土脂环酸芽孢杆菌最为常见。许多被公认安全的乳酸菌对脂环酸芽孢杆菌具有抑菌活性。为了研究乳酸菌抑制脂环酸芽孢杆菌的机理，该研究从分离自中国传统泡菜的乳酸菌中，筛选出对酸土脂环酸芽孢杆菌DSM 3922^T具有较强抑菌活性的植物乳杆菌509,采用非靶向代谢组学分析了酸土脂环酸芽孢杆菌DSM 3922^T受植物乳杆菌509抑制时的代谢产物变化，受抑制后的酸土脂环酸芽孢杆菌DSM 3922^T中上调的代谢物有308个，下调的代谢物有666个，它们主要位于氨基酸代谢、核酸代谢、糖代谢、TCA循环、细胞壁合成和跨膜运输等通路中，其中大部分氨基酸及其氨基酰类、核苷及其磷酸盐类等物质均受到下调。研究结果表明，酸土脂环酸芽孢杆菌DSM 3922^T中许多参与重要生物途径的中间代谢物受到植物乳杆菌509的抑制，而这些代谢物的下调反过来又促使酸土脂环酸芽孢杆菌自身凋亡，从而达到抑菌效果。     

基于近红外光谱的橙汁中酸土脂环酸芽孢杆菌的生长预测

酸土脂环酸芽孢杆菌（Alicyclobacillus acidoterrestris）是引起橙汁劣变的主要微生物，为研究酸土脂环酸芽孢杆菌在橙汁中的生长规律，利用近红外光谱获取橙汁中酸土脂环酸芽孢杆菌含量的信息，采用标准化（autoscale）、多元散射校正（multiplicative scatter correction,MSC）、标准正态变换（standard normal variate,SNV）、去趋势化（detrend）对光谱进行预处理，结合化学计量学，构建近红外光谱与酸土脂环酸芽孢杆菌含量预测模型。在此基础上，将近红外光谱转换为酸土脂环酸芽孢杆菌预测菌落数据，并采用“一步法”直接基于预测菌落数构建橙汁中酸土脂环酸芽孢杆菌的生长模型。结果表明，利用标准化进行光谱预处理建立的偏最小二乘（partial least squares,PLS）模型对橙汁中酸土脂环酸芽孢杆菌含量的预测效果相对较好，其预测决定系数（prediction determination coefficient,Rp2）与预测均方根误差（root mean square error of prediction...     

环介导等温扩增技术检测食品中酸土环脂芽孢杆菌

目的：利用环介导等温扩增技术建立食品中酸土环脂芽孢杆菌快速检测方法。方法：针对酸土环脂芽孢杆菌16S序列设计特异引物,再优选反应体系,用显色法检测实验结果。结果：该方法能够在63 ℃条件下1 h内检出食品中酸土环脂芽孢杆菌,所设计的引物有良好的特异性;灵敏度达6.7 CFU/mL（弱阳性）。结论：该方法具有高效、特异性强和敏感性高等特点,可满足酸土环脂芽孢杆菌快速检测筛选的要求。     

酸土脂环酸芽孢杆菌危害及其控制研究进展

酸土脂环酸芽孢杆菌(Alicyclobacillus acidoterrestris)是引起酸性果汁腐败的主要微生物,有嗜酸耐热的双重特性,其芽孢有更强的耐酸热能力,常规巴氏杀菌无法将其杀灭,对果汁工业的灭菌工艺提出了严峻挑战。控制酸土脂环酸芽孢杆菌是食品研究领域和果汁产业普遍关注的问题。本文系统概述了酸土脂环酸芽孢杆菌的特性、危害、鉴定与检测及控制该菌芽孢污染的物理、化学和理化结合法,以期为进一步研究酸土脂环酸芽孢杆菌芽孢的危害控制提供理论指导。     

介质阻挡放电等离子体对不同pH值生长的酸土脂环酸芽孢杆菌的灭活作用

该研究探讨了介质阻挡放电等离子体对不同pH值（3.2、3.6、4.0和4.4）下生长的酸土脂环酸芽孢杆菌的杀灭作用。研究发现等离子体对最适生长pH值4.0下的酸土脂环酸芽孢杆菌杀灭效率最低,pH值升高（4.4）或降低（3.2、3.6）均引起致死率增加（P<0.05）。例如30 kV处理2 min条件下,等离子体对pH值为4.0生长的酸土脂环酸芽孢杆菌致死率为4.8个对数,对pH值为3.2、3.6和4.4生长的菌体致死率分别为5.9、5.4和5.1个对数。等离子体对不同pH值培养的酸土脂环酸芽孢杆菌致死率的差异可能与菌体形态和膜脂质成分有关。扫描电镜观察发现,pH值3.2和3.6培养的菌体出现异常伸长形态,且酸土脂环酸芽孢杆菌在pH值3.2条件下更为明显,更易被等离子损伤而导致死亡。气相-质谱联用结果表明相比于最适pH值4.0,pH值4.4生长条件下环己烷十一酸相对含量显著提高（67.86%）,而环戊烷十三酸降低（22.21%）（P<0.05）,使得等离子体产生的氧自由基等成分在细胞膜中的堆积,而导致菌体更易被杀灭。该研究表明菌体耐受性增加与酸土脂环酸芽孢杆菌细胞膜脂肪酸成分和形态变化存在一定的相关性。     

改良LAMP快速检测酸土脂环酸芽胞杆菌的 研究

建立改良环介导等温扩增(loop-mediated isothermal amplification,LAMP)检测酸土脂环酸芽胞杆菌的方法。以酸土脂环酸芽胞杆菌的16S r RNA基因保守区域设计4条特异性引物,优化反应体系,通过荧光曲线、琼脂糖凝胶电泳和白色沉淀判定扩增结果。同时,对LAMP引物特异性、灵敏度、检出限进行研究。LAMP法在61℃,60 min内完成酸土脂环酸芽胞杆菌的检测。2株酸土脂环酸芽胞杆菌呈阳性结果,17株非酸土脂环酸芽胞杆菌呈阴性结果,表明该种检测方法具有高特异性。检测纯菌灵敏度为7.2 CFU/m L,对人工污染苹果汁样品中酸土脂环酸芽胞杆菌的检出限是18 CFU/m L。LAMP法检测酸土脂环酸芽胞杆有操作简单、灵敏度高、特异性强等优点,应用前景广阔。     

基于电子舌技术检测商业果汁中脂环酸芽孢杆菌

采用法国Alpha M.O.S.公司生产的α-Astree Ⅱ型电子舌对7 种市售果汁饮料及其接种脂环酸芽孢杆菌样品进行测定,所得数据应用主成分分析法进行辨别分析。2 种含乳类果汁饮料未能被区分开,其他5 种样品均可区分。将电子舌可区分的6 种果汁饮料接种两株脂环酸芽孢杆菌并在45 ℃条件下培养30 d,所有接种处理中均可检出脂环酸芽孢杆菌。3 种浑浊型饮料的检出量较多,大于103 CFU/mL。3 种澄清型饮料的检出量较少,小于103 CFU/mL。应用电子舌技术可将6 种接种脂环酸芽孢杆菌DSM 3922的果汁饮料与对照组区分开,4 种接种脂环酸芽孢杆菌XC-6的果汁饮料与对照组区分开,2 种接种脂环酸芽孢杆菌XC-6的混合果汁饮料和橙汁饮料同对照组未能被区分。     

益生菌对消化道胃酸和胆盐胁迫的应激机理

益生菌进入人体消化道后,会遇到高酸及胆盐等不利益生菌存活的胁迫环境。酸和胆盐胁迫可使益生菌的活性下降,影响益生功能的发挥。亚致死剂量的酸或胆盐胁迫可以提高益生菌的耐受力,有助于益生菌在消化道中的存活。因此,研究益生菌酸胁迫及胆盐胁迫应激机理具有非常重要的意义。本文主要综述益生菌酸胁迫和胆盐胁迫可能的机理,并对未来的研究方向进行探讨。     

抗应激功能食品研究概况

应激是机体受到外来刺激产生的非特异性反应，应激反应是当今社会普遍关注的问题。本文概述了应激的有关概念，对抗应激功能食品作了详尽介绍。     

单核细胞增生李斯特菌对食品加工中的胁迫响应及其机制研究进展

单核细胞增生李斯特菌（简称单增李斯特菌）在食品加工过程中经常会遇到环境胁迫,如酸胁迫、热胁迫、冷胁迫、干燥和高渗透压胁迫以及交叉胁迫等,并产生应激反应,而经过环境胁迫的单增李斯特菌可显著增强其抵抗致死性环境胁迫的能力,给食品安全带来极大危害。单增李斯特菌的酸胁迫响应机制主要包括F0F1-ATPase系统、谷氨酸脱羧酶系统以及精氨酸脱亚胺酶系统。热休克蛋白、冷休克蛋白、相容性溶质在单增李斯特菌的热胁迫、冷胁迫和干燥及高渗透压胁迫反应中起重要作用。本文从以上几方面就单增李斯特菌对环境胁迫响应及其机制的研究现状进行了综述,并提出了今后可能的研究方向,为单增李斯特菌在食品加工过程中的胁迫响应研究及防控提供指导。     

Extending the potential of evaporative cooling for heat-stress relief

Factors were analyzed that limit the range of environmental conditions in which stress from heat may be relieved by evaporative cooling in shaded animals. Evaporative cooling reduces air temperature (Ta), but increases humidity. Equations were developed to predict Ta reduction as a function of ambient temperature and humidity and of humidity in cooled air. Predictions indicated that a reduction of Ta becomes marginal at humidities beyond 45%. A reduction of Ta lessens with rising ambient Ta. The impact of increasing humidity on respiratory heat loss (Hre) was estimated from existing data published on Holstein cattle. Respiratory heat loss is reduced by increased humidity up to 45%, but is not affected by higher humidity. Skin evaporative and sensible heat losses are determined not only by the humidity and temperature gradient, but also by air velocity close to the body surface. At higher Ta, the reduction in sensible heat loss is compensated for by an increased demand for Hre. High Hre may become a stressor when panting interferes with resting and rumination. Effects of temperature, humidity, air velocity, and body surface exposure to free air on Hre were estimated by a thermal balance model for lactating Holstein cows yielding 35 kg/d. The predictions of the simulations were supported by respiratory rate observations. The Hre was assumed to act as a stressor when exceeding 50% of the maximal capacity. When the full body surface was exposed to a 1.5 m/s air velocity, humidity (15 to 75%) had no significant predicted effect on Hre. For an air velocity of 0.3 m/s, Hre at 50% of the maximum rate was predicted at 34, 32.5, and 31.5° C for relative humidities of 55, 65, and 75%, respectively. Similar results were predicted for an animal with two-thirds of its body surface exposed to 1.5 m/s air velocity. If air velocity was reduced for such animals to 0.3 m/s, the rise in Hre was expected to occur at approximately 25° C and 50% relative humidity. Maximal rates of Hre were estimated at 27 to 30° C when ambient humidity was 55% relative humidity and higher. High humidity may stress animals in evaporative cooling systems. Humidity stress may be prevented by a higher air velocity on the body surface of the animal, particularly in sheltered areas in which the exposed body surface is reduced, such as mangers and stalls. This may extend the use of evaporative cooling to less dry environments.     

Prospects of Breeding Quinoa for Tolerance to Abiotic Stress

Aspects related to the breeding of quinoa for increased tolerance against frost, drought, and salinity are presented with special emphasis on the conditions existing in the Peruvian Andes. Evidence from the literature indicates that plants' responses to these stresses are essentially similar, and the physiological processes involved are interrelated. The evidence suggests that tolerance to abiotic stress is polygenicallyinherited, justifying the application of appropriate plant breeding methods. A compilation of meteorological studies is presented that can be used to define the specific climatic phenomena of night frosts occurring in the quinoa-growing region of the Andes and to specify the conditions for selection of tolerant varieties. A composite-bulk breeding scheme is proposed that could be useful for highly efficient breeding of quinoa varieties. Possible future application of molecular-marker-assisted selection is discussed.     

Prospects of Breeding Quinoa for Tolerance to Abiotic Stress

Aspects related to the breeding of quinoa for increased tolerance against frost, drought, and salinity are presented with special emphasis on the conditions existing in the Peruvian Andes. Evidence from the literature indicates that plants' responses to these stresses are essentially similar, and the physiological processes involved are interrelated. The evidence suggests that tolerance to abiotic stress is polygenicallyinherited, justifying the application of appropriate plant breeding methods. A compilation of meteorological studies is presented that can be used to define the specific climatic phenomena of night frosts occurring in the quinoa-growing region of the Andes and to specify the conditions for selection of tolerant varieties. A composite-bulk breeding scheme is proposed that could be useful for highly efficient breeding of quinoa varieties. Possible future application of molecular-marker-assisted selection is discussed.     

应力分等设备在胶合木生产中的应用

近年来,胶合木的优势日渐凸显,其制备工艺与应用愈来愈成熟。本文主要介绍了胶合木制备中木材分等工艺的设备应用。胶合木制备中前期的分级工艺是影响胶合木质量的主要因素。因此,使用应力分等设备对木材进行强度分等要做到快速、准确,使生产连续化。     

The impact of the postharvest environment on the viability and virulence of decay fungi

Postharvest decay of fruits, vegetables, and grains by fungal pathogens causes significant economic losses. Infected produce presents a potential health risk since some decay fungi produce mycotoxins that are hazardous to human health. Infections are the result of the interplay between host resistance and pathogen virulence. Both of these processes, however, are significantly impacted by environmental factors, such as temperature, UV, oxidative stress, and water activity. In the present review, the impact of various physical postharvest treatments (e.g., heat and UV) on the viability and virulence of postharvest pathogens is reviewed and discussed. Oxidative injury, protein impairment, and cell wall degradation have all been proposed as the mechanisms by which these abiotic stresses reduce fungal viability and pathogenicity. The response of decay fungi to pH and the ability of pathogens to modulate the pH of the host environment also affect pathogenicity. The effects of the manipulation of the postharvest environment by ethylene, natural edible coatings, and controlled atmosphere storage on fungal viability are also discussed. Lastly, avenues of future research are proposed.