微生物絮凝剂及其絮凝微生物的研究进展

介绍了近几年来国内外微生物絮凝剂和絮凝微生物的一些发展概况,列举了近几年发现的一些微生物絮凝剂的物质属性和组成,重点讨论了胞外絮凝剂和絮凝酵母的絮凝机理,详细综述了絮凝微生物的遗传学方面的研究进展,分析讨论微生物絮凝剂的应用概况,提出微生物絮凝剂的发展趋势和研究方向。     

生物絮凝剂的最新研究进展及其应用

从絮凝剂的来源和分子组成两方面对生物絮凝剂进行了系统分类,综述了生物絮凝剂产生菌的筛选模型以及生物絮凝剂在水处理和发酵工业中的应用,详细阐述了目前国内外提出的几种不同的生物絮凝剂絮凝机理,进而在此基础上剖析了目前生物絮凝剂研究工作中仍然存在的问题,并提出生物絮凝剂今后的主要研究方向。     

微生物絮凝剂及其絮凝机理的研究概况

阐述了产絮凝剂微生物及其筛选,以及微生物絮凝剂的制取和性能的研究概况;探讨了微生物絮凝剂的絮凝机理和应用前景。     

生物絮凝剂的最新研究进展及其应用*

从絮凝剂的来源和分子组成两方面对生物絮凝剂进行了系统分类,综述了生物絮凝剂产生菌的筛选模型以及生物絮凝剂在水处理和发酵工业中的应用,详细阐述了目前国内外提出的几种不同的生物絮凝剂絮凝机理,进而在此基础上剖析了目前生物絮凝剂研究工作中仍然存在的问题,并提出生物絮凝剂今后的主要研究方向。     

微生物絮凝剂产生菌的研究进展

微生物絮凝剂是一类新型絮凝剂。絮凝剂产生菌作为微生物絮凝剂的一个科研重点已经得到广泛的研究。本文主要总结了微生物絮凝剂产生菌的一些研究进展,重点对絮凝剂产生菌的种类、筛选、培养条件、生物学机理等进行了阐述。此外还介绍了国内外几个新的研究方向,并就以后的研究趋势作了展望。     

一株絮凝菌的鉴定、絮凝基因定位及其絮凝剂成分分析

从武汉市综合废水处理的活性污泥中筛选得到一株絮凝剂产生菌株MBF03,其絮凝率达到90％以上,絮凝效果稳定.通过16S rDNA鉴定,该菌为泛菌属,扫描电镜结果显示为杆状.通过质粒转化与质粒消除试验,初步证实了MBF03菌的絮凝基因位于染色体上.提取该菌所产的絮凝剂,进行紫外、红外分析,结果表明,该絮凝剂主要成分是胞外多糖类物质,不含蛋白质和核酸.     

几株絮凝剂产生菌的特性研究

筛选到８３株絮凝剂产生菌，其中絮凝活性最高的四株分属于芽孢乳杆菌属、节细菌属、假单胞菌属、气单胞菌属。四株菌在生长过程中均可产生胞外絮凝物质，在最适培养条件下絮凝剂产量为０．５－０．９ｇ／Ｌ。纯化后的四种絮凝剂中，三种为核蛋白，一种为糖蛋白，均为高分子量物质（ＭＷ＞１０＾６）。四株菌均不含质粒。１２－３０ｇ／Ｌ的絮凝剂在１小时内对所有供试材料均有较好的絮凝效果。动物急性毒性实验表明。     

高效微生物絮凝剂D6对屠宰废水的应用研究

筛选出一株针对屠宰废水有高效絮凝活性的微生物絮凝剂产生菌,并对其所产微生物絮凝剂D6进行单因子絮凝条件优化和正交试验优化得到最佳絮凝条件。絮凝条件包括:微生物絮凝剂D6投加量、pH、金属离子种类、1%CaCl₂投加量。试验中发现碱性环境是微生物絮凝剂D6发挥絮凝活性的前提,表明微生物絮凝剂D6分子链的充分伸展对絮凝作用起决定因素,因此微生物絮凝剂D6的絮凝机理为吸附架桥作用。其最佳絮凝条件为微生物絮凝剂D6的投加量为25mL·L^-1,1%CaCl₂投加量55mL·L^-1,pH为8。在最佳絮凝条件下,絮凝率为96.6%,浊度去除率为97.8%,SS去除率为92.6%。     

黄孢原毛平革菌BKMF-1767产絮凝剂PCF-1767的絮凝特性及其机理解析

【背景】传统絮凝剂的使用会带来安全和环境污染方面的问题,而微生物絮凝剂具有无毒、无二次污染、易生物降解的优点,因此寻找高效廉价的微生物絮凝剂具有重要意义。【目的】研究黄孢原毛平革菌BKMF-1767产生的胞外多糖絮凝剂的絮凝特性及机理。【方法】使用高岭土进行PCF-1767的絮凝活性测定,分析絮凝剂获取时间、Ca2+浓度、投加量、pH、温度对絮凝效率的影响,并测定PCF-1767的热稳定性。测定絮凝剂的单糖组成、糖苷键连接类型、多糖分子量、Zeta电位变化、对絮体形态观察,探讨了PCF-1767的絮凝机理。【结果】培养6–12 d获得的PCF-1767的絮凝活性良好;7 d絮凝剂要获得较好的絮凝效率至少需加入2 mmol/L Ca2+作为助凝剂,最佳投加浓度为0.75–1.35 mg/L,最适pH为3.0-9.0,对温度高于50°C的废水絮凝活性逐渐降低,经过沸水浴处理3 h后的絮凝活性几乎不变。PCF-1767中多糖的一级结构主要由葡萄糖以→4)Glup(1→的方式连接,多糖分子量随培养时间的延长而增大,变化范围为9.897×105–2.126×106 Da。结合Zeta电位变化与絮体显微图像分析表明其絮凝机理主要为吸附架桥和卷扫作用,而非电荷中和作用。【结论】PCF-1767具有很高絮凝活性,其用量低、适用条件广、热稳定性高,是一种非常具有应用前景的絮凝剂。     

乌勇布拉克盐湖嗜盐古菌絮凝效果筛选及活性检测

【目的】从嗜盐古菌中筛选可产生生物絮凝剂的菌株,对发酵液、上清液、菌悬液、胞外聚合物的絮凝作用进行检测,筛选能够适应高盐废水处理,且具有广谱盐度及pH作用范围的微生物絮凝剂。【方法】以新疆乌勇布拉克干盐湖沉积物为研究对象,利用纯培养方法对嗜盐古菌进行分离,对絮凝菌株进行初筛及16S rRNA基因测序,构建系统进化树,初步判断菌株分类地位;复筛检测不同生物材料的絮凝效果;选择絮凝效果较好的生物材料,检测其盐度、pH的絮凝效果稳定性。【结果】采用纯培养方法共分离到28株嗜盐古菌,絮凝初筛共筛选出16株嗜盐古菌,分布于碱线菌属(Natrinema)、盐缓长菌属(Halopiger)和盐土生菌属(Haloterrigena)。菌株发酵液、上清液、菌悬液、胞外聚合物具有不同程度的絮凝效果。菌株A279-1、A133、RP33、NGA0064、RM-152、A389的发酵液、上清液的絮凝效果较好,其中菌株A389的发酵液絮凝率为61.06%,上清液为67.92%。所有菌株菌悬液的絮凝率达到80%以上。菌株所产胞外聚合物表现出较好的絮凝效果,菌株RM-152所产胞外聚合物的絮凝率最高,达89.86%,其次是A389 (81.53%)。菌株A389所产胞外聚合物的产量最大,达12.53 g/L,具有广泛的盐度和pH适应性。【结论】乌勇布拉克干盐湖沉积物中蕴含丰富的可产生微生物絮凝剂的嗜盐古菌资源。嗜盐古菌菌株发酵液、上清液、菌悬液及胞外聚合物均具有良好的絮凝作用,尤其是胞外聚合物表现出较好的絮凝效果,具有广谱的盐度和pH耐受性。嗜盐古菌所产生物絮凝剂的发现对于后续高盐废水功能材料开发具有重要应用价值。     

Recent advances in extracellular biopolymer flocculants

Extracellular biopolymer flocculants (EBFs) are flocculating substances, consisting of polysaccharides, proteins, and lipids, which are secreted in the culture broth by many microorganisms. Some of EBFs have attracted much attention as biodegradable and nontoxic substitutes for conventional chemical flocculants. This paper reviews the recent development of EBFs. Aspects discussed include an introduction to conventional chemical flocculants and EBFs, isolation of novel bioflocculant-producing microorganisms, culture conditions, chemical structure and molecular weight of EBFs, the physico-chemical factors affecting flocculating activity, fermentation process design and recent and emerging application fields of EBFs.     

Extracellular biopolymeric flocculants. Recent trends and biotechnological importance

Many microorganisms secrete extracellular biopolymeric flocculants (EBFs) in the culture broth. This work reviews the development of EBF research and applications. Aspects discussed include a comparison of the chemical and biological flocculating agents, isolation of EBF-producing microorganisms, culture conditions, mechanisms of flocculation, the chemical structure of EBFs, and the role of physicochemical factors in the flocculating activity.     

High ecosystem stability of evergreen broadleaf forests under severe droughts

Global increase in drought occurrences threatens the stability of terrestrial ecosystem functioning. Evergreen broadleaf forests (EBFs) keep leaves throughout the year, and therefore could experience higher drought risks than other biomes. However, the recent temporal variability of global vegetation productivity or land carbon sink is mainly driven by non‐evergreen ecosystems, such as semiarid grasslands, croplands, and boreal forests. Thus, we hypothesize that EBFs have higher stability than other biomes under the increasingly extreme droughts. Here we use long‐term Standardized Precipitation and Evaporation Index (SPEI) data and satellite‐derived Enhanced Vegetation Index (EVI) products to quantify the temporal stability (ratio of mean annual EVI to its SD), resistance (ability to maintain its original levels during droughts), and resilience (rate of EVI recovering to pre‐drought levels) at biome and global scales. We identified significantly increasing trends of annual drought severity (SPEI range: ?0.08 to ?1.80), area (areal fraction range: 2%–19%), and duration (month range: 7.9–9.1) in the EBF biome over 2000–2014. However, EBFs showed the highest resistance of EVI to droughts, but no significant differences in resilience of EVI to droughts were found among biomes (forests, grasslands, savannas, and shrublands). Global resistance and resilience of EVI to droughts were largely affected by temperature and solar radiation. These findings suggest that EBFs have higher stability than other biomes despite the greater drought exposure. Thus, the conservation of EBFs is critical for stabilizing global vegetation productivity and land carbon sink under more‐intense climate extremes in the future.     

Early B-cell factors involve in the tumorigenesis and predict the overall survival of gastric cancer

Gastric cancer (GC) is a heavy health burden around the world, which is the fifth most frequent tumor and leads to the third most common cancer-related deaths. It is urgent to identify prognostic markers as the guideline for personalized treatment and follow-up. We accessed the prognostic value of Early B-cell factors (EBFs) in GC. A total of 415 GC tissues and 34 normal tissues from The Cancer Genome Atlas Stomach Adenocarcinoma (TCGA-STAD) cohort, 616 external patients from {"type":"entrez-geo","attrs":{"text":"GSE15459","term_id":"15459"}}GSE15459, {"type":"entrez-geo","attrs":{"text":"GSE22377","term_id":"22377"}}GSE22377, {"type":"entrez-geo","attrs":{"text":"GSE51105","term_id":"51105"}}GSE51105, {"type":"entrez-geo","attrs":{"text":"GSE62245","term_id":"62245"}}GSE62245 were enrolled for analysis. Univariate and multivariate Cox regression analyses were employed to evaluate the sole and integrative prognostic value of EBFs, respectively. Genetic alterations, DNA methylation of EBFs were also evaluated, as well as the involved signaling pathways. We revealed that increased EBFs associated with the poor prognosis of GC patients, the prognostic model was established in TCGA-STAD cohort, and validated in Gene Expression Omnibus (GEO) cohorts, with effectiveness in both HER2 positive and negative patients. DNA methylation was involved in the impact on prognosis. Cell cycle, immune-associated, and MAPK pathways were influenced by EBFs. Anti-CTLA4 immunotherapy is more suitable for EBFs determining high-risk groups, but not anti-PD-1/PD-L1 therapy. 5-Fluorouracil, methotrexate, vorinostat are suitable to inhibit the function of EBFs. Our new findings provide novel insight into the prediction of prognosis and clinical treatment of GC patients based on EBFs.     

Differential protein expression in early Atlantic cod larvae (Gadus morhua) in response to treatment with probiotic bacteria

Proteome analysis was used to study the effects of probiotic bacteria treatment on the protein expression in early Atlantic cod (Gadus morhua) larvae. The main focus was on proteins connected to immune function, growth and development. The results demonstrated that none of the identified cod larvae proteins showing up-regulation after administration of probiotic bacteria are known to have a function in immunity. In contrast, several proteins exhibiting down-regulation after exposure to the probiotic bacteria may be related to stress and immune responses. This indicates that the probiotic treated larvae were experiencing a lower level of immune-stimulation than the control group. It is therefore tempting to postulate that the probiotic bacteria mixture used in the present study reduced the environmental stress by inhibiting the growth of pathogenic bacteria. Most of the identified up-regulated proteins in the probiotic group relative to the control may be linked to growth and development. The most pronounced up-regulation of proteins was found in several muscle α-actin isoforms indicating improved growth upon probiotic bacteria treatment.     

乳酸菌的安全性研究

乳酸菌通常被认为是安全的,但在机体免疫抑制、肠道发育未成熟、肠上皮受损等情况下,可以导致心内膜炎、菌血症、局部性感染等临床症状.本文综述了国外有关乳酸菌的致病性、抗药性基因转移方面研究的一些新进展,以期引起国内对乳酸菌安全性问题的重视.     

斜纹夜蛾幼虫肠道细菌分离鉴定及其功能初步分析

昆虫肠道微生物对其寄主的生长发育、营养代谢、免疫以及农药抗性等方面都发挥着重要作用。为研究斜纹夜蛾Spodoptera litura幼虫肠道细菌的多样性,并为其功能验证做准备,本文利用传统微生物分离纯培养方法从斜纹夜蛾4龄幼虫肠道中共分离鉴定得到10株细菌,分别为属于变形菌门(Proteobacteria)的脱氮假单胞菌(Pseudomonas denitrificans),不动细菌(Acinetobacter sp.),肺炎克雷伯氏菌(Klebsiella pneumoniae)和肠杆菌(Enterobacter sp.);属于厚壁菌门(Firmicutes)的鸡葡萄球菌(Staphylococcus gallinarum),蒙氏肠球菌(Enterococcus mundtii),蜡样芽胞杆菌(Bacillus cereus)和枯草芽胞杆菌(Bacillus subtilis)以及放线菌门(Actinobacteria)的微杆菌(Microbacteriums sp.)和乳酪棒杆菌(Corynebacterium casei)。变形菌门和厚壁菌门是斜纹夜蛾肠道可培养细菌中的优势菌群。功能验证实验表明肠杆菌具备纤维素降解能力,微杆菌具备很强的苯酚降解能力。本研究为未来深入研究斜纹夜蛾肠道微生物的功能提供了方向和菌株材料。     

细菌在线虫生防中应用的研究进展

在具有杀线虫能力细菌的特征、作用方式及其在线虫生防中的潜在应用等方面,结合作者的研究工作,对国内、外的一些研究进展进行了综述,并提出了研究展望。     

广西三种真红树植物可培养细菌多样性及其生物活性初筛

为了挖掘真红树植物潜在细菌新物种和生物活性物质,丰富红树林微生物多样性,为新型活性产物开发提供菌株资源。该文从秋茄、木榄和红海榄三种广西来源的真红树植物及其生境中,按根、茎、叶、花、果实和泥土分成22份样品,选用8种不同培养基分离可培养细菌,通过16S rRNA基因序列鉴定,分析其多样性,采用纸片法筛选细菌发酵粗提物的抑菌活性,点植法测试其酶活性。结果表明:(1)共分离获得可培养细菌35株,隶属于23个科28个属,芽孢杆菌属占细菌总数的14.3%,为优势菌属,同时发现11株潜在的新细菌资源。(2)活性筛选获得4株细菌具有抑菌活性,16株细菌具有酶活性,芽孢杆菌属是酶活性优势菌属。综上所述,广西真红树植物可培养细菌多样性丰富,部分细菌具有抑菌活性和酶活性,在新型抗生素和酶应用方面具有一定的开发潜力。