重组大肠杆菌的发酵与代谢工程

在工程菌的发酵中,外源基因高表达条件下的高密度发酵对于提高生产效率、降低生产成本、简化产品纯化工艺以及降低扩大生产投资都具有非常重要的意义．然而在大肠杆菌的高密度发酵中遇到了许多困难［‘］,其中主要包括有机酸类代谢副产物累积并抑制细菌自身生长、供氧限制和外源基因高表达引起宿主细胞生理负担过重等问题。对此,国内外学者作了许多有意义的探索。应用代谢工程技术对工程菌进行改良,使之有利于外源基因的高表达及高密度发酵,是一项很有应用前景的研究课题,引起了广泛关注。本文拟对近年来有关应用代谢工程改良重组大肠…     

畜禽中药-益生菌复合微生态制剂的研究进展

畜禽中药-益生菌复合微生态制剂是指采用现代发酵技术将益生菌与中药联合发酵,发挥两者的协同作用,以提高畜禽免疫功能、保护畜禽健康的一种新型动物微生态制剂。文中通过调研近几年关于益生菌及中药微生态制剂等方面的文献,综述了畜禽中药-益生菌复合微生态制剂的产生背景及菌种特点,并重点阐述了畜禽中药-益生菌复合微生态制剂的作用机制、在畜禽养殖中的应用及存在问题与建议,以期为畜禽中药-益生菌复合微生态制剂的深入研究提供参考和依据。     

重组大肠杆菌高表达高密度发酵研究

大肠杆菌高密度高表达发酵技术是现代发酵工程的重要研究课题,此项技术可以有效地提高大肠杆菌的产量和外源重组蛋白的表达量,该文就影响大肠杆菌高密度发酵的主要因素如宿主菌类型、培养基组成、培养条件、生长抑制物质、补料调控等进行了阐述和讨论。     

巴斯德毕赤酵母(P.pastoris)高密度发酵研究进展

高密度发酵已经成为提高毕赤酵母目的蛋白表达量的关键技术之一,而其中发酵工艺又是高密度发酵的一个重要因素。主要从巴斯德毕赤酵母遗传学特性、表达宿主菌、表达载体、外源蛋白的表达方面进行了阐述,并从毕赤酵母工程菌的选择、培养基的优化设计、发酵过程关键参数调控以及甲醇诱导等方面阐述毕赤酵母的高密度发酵。最后,提出了巴斯德毕赤酵母高密度发酵过程中存在的问题并进行展望。     

基于毕赤酵母系统表达的重组自身免疫调节生物制剂的研究进展

免疫调节制剂的靶目标为免疫系统相关分子如细胞因子、共刺激分子等,在治疗自身免疫病中很有潜力。免疫调节制剂的生产需要合适的表达系统,而毕赤酵母系统具有便于基因操作、易培养和高密度发酵等特征;更重要的是,毕赤酵母为真核细胞,可进行翻译后修饰并分泌可溶性的正确折叠的重组蛋白,其生物活性及功能也得到相应提高,这些优势使得毕赤酵母成为高效实用的蛋白表达宿主。我们就毕赤酵母系统表达的用于治疗自身免疫病的几种免疫调节制剂的研究进展做简要综述。     

益生菌调节肠上皮细胞免疫反应的研究进展

肠道不仅是消化吸收的场所,而且是人体重要的免疫器官。益生菌通常被认为是胃肠道共生菌,摄入适量时,可对宿主产生益处。现就益生菌可调节肠道屏障功能,并通过固有免疫和适应性免疫反应来调节肠上皮细胞介导的免疫反应的相关研究作一综述,为开发新型益生菌制剂,抑制肠道病原菌提供了研究思路。     

益生菌、益生元和消化酶

本文对肠道腐败的主要原因是由于消化酶不足所致的新观念作了介绍,并对人们容易误解的关于益生菌、益生元和合生元的定义作了阐述。介绍了国内外益生菌制剂的一些新动向。鉴于我国乳酸发酵中数量庞大的乳酸菌废菌体作为废物而排放,不仅污染环境,还浪费资源,建议能加以回收,为益生菌的廉价大量生产和普及使用创造条件。     

微生态制剂影响致腹泻肠道病毒感染机制进展

肠道是一个复杂的生态系统,也是多种寄生微生物与动物宿主之间相互共生的地点。寄生菌/共生菌对维持肠道的生态系统平衡具有重要作用。但外来病原性微生物如病毒等可打破生态平衡。而微生态制剂如益生菌可缩短病毒性腹泻的病程。本文介绍了肠道上皮生态系统以及病毒致腹泻机制,并对益生菌干涉致腹泻的主要病毒机制进行了综述。     

重组大肠埃希菌发酵工艺的影响因素及策略

重组大肠埃希菌的高密度发酵是现代发酵工程研究的一个热点 ,也是基因工程产品大规模生产的重要技术。采用高密度培养技术 (Ｈｉｇｈｃｅｌｌ ｄｅｎｓｉｔｙｃｕｌｔｒｅ,ＨＣＤＣ) ,也就是高密度发酵技术 ,提高菌体的发酵密度 ,最终提高产物的比生产率 ,不仅可减少培养体积、优化下游分离提取 ,还可以缩短生产周期、降低生产成本 ,从而极大地提高在市场上的竞争力。这一目的的实现 ,除了重组菌本身的表达性质外 ,还必须赋予重组菌生长和产物表达的最适环境条件 ,包括适宜的培养基组成、宿主菌的选择、补料的调控、代谢副产物的限制、比生…     

重组大肠杆菌高密度发酵研究进展

重组大肠杆菌的高密度发酵是提高基因工程产品产量的一个非常有铲的手段,是现代发酵工程研究的一个热点。本文就高密度发酵中影响重组大肠杆菌发酵产率的几个因素,包括宿主菌、培养基、培养条件、补料方法以及高密度发酵过程中存在的问题和对策加以讨论,着重探讨了高密度下大肠杆菌产生的有害代副产物－－乙酸的产生机制、抑制作用机理,以及控制乙酸机累的技术方法。     

Functional petit-suisse cheese: measure of the prebiotic effect

Prebiotics and probiotics are increasingly being used to produce potentially synbiotic foods, particularly through dairy products as vehicles. It is well known that both ingredients may offer benefits to improve the host health. This research aimed to evaluate the prebiotic potential of novel petit-suisse cheeses using an in vitro fermentation model. Five petit-suisse cheese formulations combining candidate prebiotics (inulin, oligofructose, honey) and probiotics (Lactobacillus acidophilus, Bifidobacterium lactis) were tested in vitro using sterile, stirred, batch culture fermentations with human faecal slurry. Measurement of prebiotic effect (MPE) values were generated comparing bacterial changes through determination of maximum growth rates of groups, rate of substrate assimilation and production of lactate and short chain fatty acids. Fastest fermentation and high lactic acid production, promoting increased growth rates of bifidobacteria and lactobacilli, were achieved with addition of prebiotics to a probiotic cheese (made using starter+probiotics). Addition of probiotic strains to control cheese (made using just a starter culture) also resulted in high lactic acid production. Highest MPE values were obtained with addition of prebiotics to a probiotic cheese, followed by addition of prebiotics and/or probiotics to a control cheese. Under the in vitro conditions used, cheese made with the combination of different prebiotics and probiotics resulted in the most promising functional petit-suisse cheese. The study allowed comparison of potentially functional petit-suisse cheeses and screening of preferred synbiotic potential for future market use.     

益生菌的安全性

益生菌是指一类活的,摄入足够量就能够对人体产生有益作用的微生物,目前广泛应用于食品发酵、工业乳酸发酵以及医疗保健领域.随着市场上商品化益生菌的不断出现,它所带来的安全性问题也更加引起人们的关注.目前益生菌主要存在四个方面的安全问题:致病性和感染能力;有害的代谢活动:过度的免疫反应和可能的基因转移.传统的益生菌安全性评价方法具有一定的局限性.我们需要针对目前益生菌安全性存在的问题建立一套包含基因组学,代谢组学,蛋白质组学等研究内容的评估方法,对益生菌的安全性进行系统全面的评估.本文总结了一些对于益生菌安全性的研究进展和研究方法,以提示我国应尽快完善益生菌及其制品的安全性评价方法指标并建立安全性评价体系,使益生菌更好的为人们的健康服务.     

Evaluation of native potential probiotic bacteria using an in vitro ruminal fermentation system

Rumen microbiota provides an important source of protein to grazing animals and produces volatile fatty acids (VFA), the main energy source for ruminants generated by fibre fermentation. Probiotics can be used to modulate rumen fermentation, and native microbiota is a source of potentially useful microorganisms. In this work, ruminal bacterial strains were isolated and subsequently identified, and their potential to modify fermentation patterns with wheat straw, microcrystalline cellulose and oat xylan as substrates was assessed by in vitro gas production and VFA fermentation patterns. Four of the isolates were identified as Pseudobutyrivibrio ruminis and two corresponded to new members of the Lachnospiraceae family. The addition of one P. ruminis (strain 50C) and one Lachnospiraceae (strain 21C) to the fermentation system which used wheat straw as the substrate significantly increased total VFA concentration without altering the total gas produced in one case and showed a decrease in total gas production in the other. All bacterial strains induced higher butyric acid concentrations with the three substrates (up to 31 mM in the case of Lachnospiraceae 21C incubated with oat xylan and 25 mM in microcrystalline cellulose fermenters to which P. ruminis 50C had been added) compared to the control, which had concentrations of <1 mM. Analysis of the fermentation products suggested that the addition of probiotics to the fermentation system had the potential to induce metabolic shifts that would result in better energy yields. These results show that native bacteria have promising features as fermentation modulators, thereby justifying further research to assess their use as probiotics for ruminants.     

重组大肠杆菌高密度发酵研究进展

重组大肠杆菌的高密度发酵是提高基因工程产品产量的一个非常有效的手段,是现代发酵工程研究的一个热点。本文就高密度发酵中影响重组大肠杆菌发酵产率的几个因素,包括宿主菌、培养基、培养条件、补料方法以及高密度发酵过程中存在的问题和对策加以讨论,着重探讨了高密度下大肠杆菌产生的有害代谢副产物———乙酸的产生机制、抑制作用机理,以及控制乙酸积累的技术方法 。     

益生菌的应用现状和发展前景

益生菌是一类严格选择的，如果给予足够的量，能够为宿主带来健康益处的活性微生物。常见的具有益生功能的微生物，包括传统益生菌乳酸菌(lactic acid bacteria)和酵母菌(Saccharomyces)等，以及下一代益生菌普拉梭菌(Faecalibacterium prausnitzii)、脆弱拟杆菌(Bacteroides fragilis)、嗜黏蛋白阿克曼菌(Akkermansia muciniphila)和普雷沃氏菌(Prevotella copri)等。益生菌与人体健康之间存在密切的关系，这些微生物可通过肠道刺激胃肠道反应或直接作用于口腔、阴道、皮肤等其他部位以调节宿主健康。因此，它们在食品、种植业、畜牧业以及医疗领域中得到广泛应用，成为改善宿主健康的有力工具。本文对乳酸菌等传统益生菌以及嗜黏蛋白阿克曼菌等下一代益生菌的功能的开发与应用进行了综述，总结了这几种益生菌在食品生产、疾病治疗以及农业生产等方面的应用潜力，展望了益生菌资源研究与应用的发展趋势，以期为研究新老益生菌功能的开发与应用提供参考。     

Top‐down systems biology integration of conditional prebiotic modulated transgenomic interactions in a humanized microbiome mouse model

Gut microbiome–host metabolic interactions affect human health and can be modified by probiotic and prebiotic supplementation. Here, we have assessed the effects of consumption of a combination of probiotics (Lactobacillus paracasei or L. rhamnosus) and two galactosyl‐oligosaccharide prebiotics on the symbiotic microbiome–mammalian supersystem using integrative metabolic profiling and modeling of multiple compartments in germ‐free mice inoculated with a model of human baby microbiota. We have shown specific impacts of two prebiotics on the microbial populations of HBM mice when co‐administered with two probiotics. We observed an increase in the populations of Bifidobacterium longum and B. breve, and a reduction in Clostridium perfringens, which were more marked when combining prebiotics with L. rhamnosus. In turn, these microbial effects were associated with modulation of a range of host metabolic pathways observed via changes in lipid profiles, gluconeogenesis, and amino‐acid and methylamine metabolism associated to fermentation of carbohydrates by different bacterial strains. These results provide evidence for the potential use of prebiotics for beneficially modifying the gut microbial balance as well as host energy and lipid homeostasis.     

Studies of some physical parameters for large scale protease production by SSF

For designing the large scale protease production system, through solid state fermentation, the important parameters are accumulation density, bed height, aeration etc. The optimum fermentation condition recorded were 0.3125 g/cc accumulation density and 1.0 cm bed height (without aeration). Aeration at 3 LPM and 2.0 cm bed height were found optimum for protease production by Rhizopus oryzae.     

Fermentation technologies for the production of probiotics with high viability and functionality

There is growing scientific evidence supported by mechanistic and clinical studies that probiotics can provide health benefits. As probiotics are highly sensitive to many environmental factors, and because the propagation of many strains of intestinal origin is not straightforward, most commercial strains are selected on the basis of their technological properties - ruling out some strains with promising health properties. To date, probiotic production has almost exclusively been carried out using conventional batch fermentation and suspended cultures, in some cases combined with the use of sublethal stresses to enhance cell viability, the addition of protectants or microencapsulation to provide cell protection. However, other less conventional fermentation technologies, such as continuous culture and immobilized cell systems, could have potential for enhancing the performance of these fastidious organisms. These technologies might be employed to develop strains with improved physiology and functionality in the gut and to enlarge the range of commercially available probiotics, as well as expanding product applications.     

Antagonistic activity of lactobacilli isolated from natural ecotopes

Lactobacilli are widely used in silage production, for fermentation of foodstuffs, and as probiotics. Their therapeutic effect in preparations is based on their antagonistic activity against pathogens. In this work, antagonistic activity of Lactobacillus strains isolated from silage and fermented plant-derived foodstuffs was studied in order to select the strains promising for industry, agriculture, and medicine. Twenty Lactobacillus strains were ranked according to the intensity and rate of acid production and antibiotic resistance. Lactobacillus sp. Cа9L was selected as a promising starter culture strain for biotechnology based on the optimal combination of acid production, rate of acidification, and antibiotic resistance.     

Probiotics – do they have a role in the pig industry?

The delivery of certain living microorganisms in food has long been suggested as having positive health effects in humans. This practice has extended into food animal production, with a variety of microorganisms being used; lactic acid bacteria, various Bacillus species and the yeast Saccharomyces cerevisiae have been particularly used in the pig industry. The increased interest in probiotics is essentially due to the problem of microbial resistance to antibiotics and following the ban of the use of antibiotics in animal production, probiotics being considered an alternative means to reduce pathogen infection and improve animal health especially around the time of weaning. However, there is still a need to clarify the probiotic effectiveness in pigs, and the underlying mechanisms. When assessing the efficacy of probiotics one must consider the particular strain of organism being used and the production stage of the pigs being treated. The reproducible delivery of probiotics in industrial pig production is problematic as maintenance of viability is key to their beneficial activity, but difficult to achieve with commonly used feed processing technologies. One specific context where probiotics organisms may be reliably delivered is in systems utilising fermented liquid feeds. Liquid feed may be fermented by the activity of wild lactic acid bacteria or may be stimulated using specific isolates as 'starters'; the latter system has advantages in terms of reproducibility and speed of fermentation. The farm context in which the organism is used is likely to be critical; the use of probiotics is more likely to result in measurable economic gains in animals living in sub-optimal conditions rather than in those reared in the highest welfare and husbandry conditions. The establishment of a beneficial lactic acid bacteria population at birth may lead to healthier animals, this may be most effectively achieved by treating sows, which provide an amplification step and flood the neonatal pigs' environment with desirable bacterial strains. In contrast, it may be sufficient to provide a supportive, protective microbiota around the time of weaning as this is a time of major crisis with instability and loss of certain bacterial populations.