The flocculation efficiency of compound bioflocculant by flocculant-producing bacteria

The flocculation efficiency of compound bioflocculant produced by flocculant-producing bacteria was investigated in this study. Cheap cellulose was selected as the substrate for the production of a lower cost bioflocculant. The end product of cellulose decomposing bacteria was utilized as substrate for flocculant-producing bacteria. The optimum fermentation conditions were determined as follows: the initial fermentation and fermentation time was 5 d and 1 d respectively, the temperature was 30 ℃, the rotation speed was 120 r/min, the amount of CaCl2 solution （10%） was 1.5 ml/L. The flocculation test indicated that the bioflocculant had high efficiency in the removal of the turbidity raw water from Songhua River.

Comparative analysis of hydrogen-producing bacteria and its immobilized cells for characteristics of hydrogen production

A strain of hydrogen producing bacteria was immobilized by polyvinyl alcohol-boric acid method, with the addition of a small amount of calcium alginate. The immobilized cells were insensitive to the presence of traces of O2. Moreover, the immobilized cells increased both the evolution rate and the yield of hydrogen production. Batch experiments with a medium containing 10 g/L glucose demonstrated the yields of hydrogen production by the immobilized and free cells were 2.14 mol/mol glucose and 1.69 mol/mol glucose, respectively. In continuous cultures at medium retention time of 2.0 h, the yield and the evolution rate of hydrogen production by the immobilized cells were 2.31 mol/mol glucose and 1 435.4 ml/（L·h） respectively. However, at medium retention time of 6.0 h, the yield and the evolution rate of hydrogen production by free cells were only 1.75 mol/mol glucose and 362.9 ml/（L·h）, respectively.

The Feasibility of Immobilization of Bioflocculant-producing Bacteria Using Mycelial Pellets as Biomass Carriers

Bioflocculant-producing bacteria Agrobacterium tumefaciens F2 and Bacillus sphaeicus F6 were immobilized onto mycelial pellets to investigate the bioflocculant-producing potential of this combined organism and the corresponding flocculating efficiency. The atomic force microscope ( AFM) images of mycelial surface indicate that the mycelia pellet can immobilize bioflocculant-producing bacteria F2 and F6 as a biomass carrier. The flocculating efficiency of bioflocculant produced by this combined organism was studied under the optimum flocculating conditions obtained by Response Surface Methodology ( RSM ) . The fermentation yield of the combined mycelial pellet is about 2. 6 g / L,which is higher than that of the free bacteria ( only 2. 2 g / L) . Flocculating efficiency of the combined mycelial pellet was comparable with that of bioflocculant generated by the free bacteria. The bioflocculant yield is enhanced and the flocculating efficiency of the co-culture is uninfluenced after immobilized with mycelial pellet as a carrier. In conclusion,the mycelial pellet is feasible as a biomass carrier for the immobilization of bioflocculant-producing bacteria.

POLY (β-HYDROXYALKANOATES): NATURAL BIOCOMPATIBLE AND BIODEGRADABLE POLYESTERS PRODUCED BY BACTERIA

A wide variety of different types of microorganisms are known to produce intracellular energy and carbon storage products, which have been generally described as being poly (β-hydroxybutyrate), PHB, but which are, more often than not, copolymers containing different alkyl groups at the β-position. Hence, PHB belongs to the family ofpoly (β-hydroxyalkanoastes), PHA, all of which are usually formed as intracellular inclusions in bacteria under unbalanced growth conditions. Recently, it became of industrial interest to evaluate these PHA polyesters as natural biodegradable and biocompatible plastics for a wide range of possible applications, such as surgical sutures or packaging containers. For industrial applications, the controlled incorporation of repeating units with different chain lengths into a series of copolymers is desirable in order to produce polyesters with a range of material properties because physical and chemical characteristics depend strongly on the polymer composition. Such 'tailor-made' copolymers can be produced under controlled growth conditions in that, if a defined mixture of substrates for a certain type of microorganisms is supplied, a well defined and reproducible copolymer is formed.

Folate Enrichment of <i>Ogi</i>(a Fermented Cereal Gruel) Using Folate Producing Starter Cultures

This study was aimed at selecting starter cultures for bio-enriching ogi (fermented cereal gruel) using folate-producing microorganisms. The folate-producing microorganisms were isolated by incorporating folate analogue, methotrexate in the isolation medium and further screened for folate production by growth in Folic Acid Casei Medium. Folate production was quantified using 3-aminophenol spectrophotometric method. Folate-producing lactic acid bacteria from fermenting maize slurry were species of Lactobacillus, Lactococcus, Pediococcus and Leuconostoc while yeast isolates were mainly species of Candida and Saccharomyces. However, Lactobacillus plantarum X13, Pediococcus pentosaceus L73, Candida parapsilosis Y77 and Candida tropicalis Y74 were used as starter cultures singly and in combination for the fermentation and production of ogi. The highest folate concentration, 30.97 ± 0.37 μg/ml, was observed after 24 h of the co-fermentation of maize slurry with Lactobacillus plantarum X13 and Candida tropicalis Y74. This represents a triple fold of the folate concentration observed in unfermented maize slurry. The pH of the fermenting maize slurry was observed to decrease from 6.12 to 3.60, while the reducing sugars and the titratable acidities were observed to increase as fermentation progressed. Sensory evaluation of the ogi samples after fermentation showed high general acceptability comparable to the naturally fermented ogi as regards to colour, taste, flavour, aroma and texture. The data made available in this study suggest the possibility of folate enrichment of ogi and its use as a vehicle for increasing folate availability to consumers thereby preventing folate deficiency diseases prevalent in many African countries.

高光纯D-乳酸生产菌株假肠膜明串珠菌HL64-1的分离鉴定及其发酵特性

从自然界中筛选分离产酸菌是获得高光学纯度乳酸生产菌株有效的途径之一。从腐烂果实中分离获得一株产高光学纯度D-乳酸菌株HL64-1,经形态学、16S rDNA序列分析、序列相似性Blast比对分析鉴定为假肠膜明串珠菌(Leuconostoc pseudomesenteroides)。在基础发酵培养基中摇瓶发酵24 h,产D-乳酸的量达到62.18 g/L,产酸速率达2.59 g/(L·h),光学纯度达99.90%(ee);在5 L发酵罐中放大培养,通过补加碳源,发酵72 h,D-乳酸产量达到78.74 g/L,平均产酸速率达1.09 g/(L·h)。该菌株可以有效利用农业副产物花生饼粉和棉籽粉作为替代氮源以降低发酵原料成本。该菌还可利用木糖产生D-乳酸,且葡萄糖能显著提高木糖的利用效率,极具工业应用前景。

浓香型白酒发酵体系中己酸菌的研究进展

浓香型白酒发酵体系中己酸生成菌(以下简称“己酸菌”)的己酸合成代谢对提高浓香型白酒的发酵质量非常重要。因此,有必要深入全面了解浓香型白酒发酵体系中己酸菌的种类及其己酸合成代谢特征。本综述介绍了目前浓香型白酒发酵体系中已经分离的己酸菌株的种类多样性、系统进化关系、生理代谢特征、己酸合成代谢机制以及其与己酸菌、非己酸菌之间的协同代谢关系。本文可为理解己酸菌群在浓香型白酒发酵体系中的原位己酸合成代谢规律提供参考,为将来靶向提高己酸菌群在浓香型白酒发酵和生物质转化高附加值己酸工艺中进行己酸合成培养工程的应用提供理论依据。

产志贺毒素大肠埃希氏菌活菌检测方法的应用现状及展望

产志贺毒素大肠埃希氏菌作为一种重要的食源性致病菌,会对人体健康造成严重威胁。对其进行快速、准确的鉴定检测是预防和控制相关疾病的有效手段。基于此,文章对目前可用于检测活体产志贺毒素大肠埃希氏菌的方法进行综述,主要包括传统的细胞培养方法、免疫学检测方法和分子生物学方法等,并对这些方法的应用和发展前景展开了深入探讨。随着分子生物学和生物工程技术的发展,不同检测方法联合使用可以克服单一方法的缺陷,从而取得更高效、准确的检测结果。

浓香型白酒窖泥己酸菌的研究进展

浓香型白酒是中国白酒的重要类型之一,己酸乙酯是浓香型白酒特征风味物质,该物质合成所需的前体己酸主要依靠发酵过程中的己酸菌代谢生成。己酸菌的分离、鉴定及代谢功能研究已成为白酒品质提升相关领域的研究热点之一。本文综述了窖泥中己酸菌的分离概况,介绍了浓香型白酒发酵系统中常见的3种己酸菌及己酸的合成途径,探讨了pH及底物组成对己酸产量的影响;此外,介绍了微生物群落中其他微生物对己酸菌的影响,以期通过探讨浓香型白酒发酵体系中微生物驱动己酸形成的机制及其影响因素,为提升浓香型白酒品质提供理论基础。

产河豚毒素微生物的研究进展

【背景】河豚毒素(TTX)是已知毒性较强的海洋毒素之一,广泛分布于河鲀等海洋生物体内。作为典型的钠离子通道阻断剂,TTX在镇痛、戒毒和抗心律失常等医疗领域展现出巨大的应用价值。然而,因获取困难和产量低下,TTX在医药领域的应用受到制约。因此,利用微生物发酵生产TTX成为了一个备受关注的研究方向。【目的】了解TTX的概况、产TTX微生物的分布和分类学多样性、TTX的发酵生产研究及TTX在微生物和环境中的迁移机制。【进展】目前,学界对TTX的理化性质已有较为清晰的认识,但其来源仍无明确定论。自1986年以来,科研人员陆续从河鲀、蓝环章鱼(Octopus maculosus)等生物及其栖息环境中分离出约150株产TTX菌株,其中以弧菌属、芽胞杆菌属为主,这些发现不仅为TTX的微生物起源说提供了强有力的理论支撑,也为后续利用微生物发酵生产TTX的研究奠定了坚实的基础。许多学者对TTX菌株发酵产毒中关键影响因素以及TTX迁移机制进行了探究,并取得了一定的成果。【展望】未来研究可重点考虑定向改造产TTX菌株、完善菌株大规模培养条件、探索影响菌株产TTX能力的关键因素以及分析微生物群落的相互作用对其合成TTX的影响,从而为TTX生物合成机制的阐明提供借鉴。【意义】通过对产TTX微生物的综述,阐明TTX的生物合成途径,为实现TTX规模化生产,解决TTX获取困难、成本高的难题,推动其在医药领域的应用提供理论参考。

嗜盐原油降解混合菌处理采出水特性研究

针对高矿化度高硫化物的油田采出水的生物处理,从含油污泥、采出水等样品中经初筛、复筛获得嗜盐原油降解菌14株,选取降解率最高的4株进行复配,构建出嗜盐原油降解混合菌TG-1。16 SrDNA序列分析表明4株菌分别为不动杆菌(Acinetobacter);副蕈状芽胞杆菌(Bacillus paramycoides);芽孢杆菌(Bacillus sp.);肠杆菌(Enterobacter sp.)。考察了TG-1处理采出水性能,发现最适矿化度范围在30 g/L以下,最高耐受硫化物质量浓度可达150 mg/L,原油质量浓度不高于500 mg/L去除效果最好。将TG-1应用于生物接触氧化装置中,在pH值7~8、温度30℃左右、溶解氧4~5 mg/L、水力停留时间为4~12 h以及进水原油质量浓度为10~100 mg/L的条件下,出水原油质量浓度小于15 mg/L,满足克拉玛依油田注水水质标准A2。

白三叶根际产铁载体菌的分离及促生特性研究

【目的】挖掘贵州省内野生牧草根际产铁载体菌资源,为植物根际促生菌的进一步开发利用提供菌种资源,为解决植物缺铁症促进植物抗逆增产提供依据。【方法】采用土壤稀释法对白三叶根际产铁载体菌进行分离,利用定性、定量分析对其产铁载体能力进行测定,通过16S rRNA基因序列鉴定菌株,并对菌株促生特性进行检测。【结果】从贵州黔南、贵阳、铜仁地区3份白三叶根际土壤中分离得到产铁载体菌5株(TSQD-1、TSQD-2、TSGH-1、TSTY-1、TSTY-2),均属于假单胞菌属(Pseudomonas sp.),其中,菌株TSGH-1、TSQD-1和TSQD-2有较强的产铁载体能力;5个菌株均具有溶解无机磷、固氮和分泌IAA能力,其中,TSGH-1有较强的溶解无机磷能力和较高的固氮酶活性,TSTY-2具有较高的产IAA能力。【结论】贵州白三叶根际土壤产铁载体菌株均属假单胞菌属(Pseudomonas sp.),TSGH-1、TSQD-1和TSQD-2菌株同时具有溶磷、固氮和分泌IAA能力,具有多重促生特性。

仙客来枯萎病病原菌产孢培养基筛选及培养条件优化

为了获得高浓度的仙客来枯萎病病原菌的孢子悬液,通过对不同营养培养基进行初筛,再以初筛营养成分进行正交试验,得到最佳营养配比,进一步通过单因素试验对培养基的pH和培养温度进行筛选。结果表明,马铃薯、绿豆、蔗糖为仙客来枯萎病病原菌产孢培养基的最佳营养成分,最佳配比为绿豆5.0%、蔗糖0.5%、马铃薯20%,培养基最佳pH为6,最佳培养温度为30℃。研究结果明确了仙客来枯萎病病原菌的产孢条件,为仙客来枯萎病的感病机理、防治技术及孢子萌发抑制等研究奠定基础,同时对指导实际生产中科学管理、综合防治病害具有重要意义。

南极菲尔德斯半岛土壤产酶细菌的鉴定及其系统发育分析

本研究针对菲尔德斯半岛10个不同微生态环境的土壤细菌,采用专用产酶平板培养法和16SrDNA测序法分别对分离菌的产胞外酶能力及系统发育进行了分析。结果显示:大多数产淀粉酶、蛋白酶、纤维素酶、酯类水解酶和藻胶酶等的菌株主要分布在离海岸较近、动植物比较丰富的区域,而半岛内陆产酶菌的数量与种类较少。在125株产胞外酶菌中发现有87株产酶能力较高,且许多株可产两种以上的酶;另外所有分离菌均不产明胶酶、卡拉胶酶和几丁质酶。64株产胞外酶能力较好代表菌的系统发育分析表明,它们共分布于7纲、17属;其中产淀粉酶菌株为3纲、5属,产蛋白酶菌株为7纲、14属,产纤维素酶菌株为1纲、1属,产酯类水解酶菌株为4纲、7属,产七叶苷酶菌株为7纲、13属,产DNA酶菌株为5纲、11属,产过氧化氢酶菌株为2纲、2属,产氧化酶菌株为1纲、1属。另外,还发现有6株菌可能为Pedobacter,Chryseobacterium,Flavobacterium和Kaistella属内的潜在新种。上述结果为研究开发低温微生物和适冷酶提供了有价值的参考和菌种源。

头孢地尔对产金属β-内酰胺酶革兰阴性菌的作用现状研究

产金属β-内酰胺酶(MBLs)革兰阴性菌是临床常见的感染病原菌,该类菌可引起多种严重感染,其中产金属β-内酰胺酶肺炎克雷伯菌(KP)是世界范围内的重要医院获得性感染菌,对当前抗感染治疗构成严重威胁。头孢地尔作为新型头孢菌素,具有抗菌活性强、作用范围广、组织穿透力强等特点,对产碳青霉烯酶的肠杆菌、鲍曼不动杆菌、铜绿假单胞菌、嗜麦芽窄单胞菌有强大的抗菌活性,其中它对金属β-内酰胺酶也有相当好的活性。本研究针对头孢地尔对产金属β-内酰胺酶革兰阴性菌的作用进行了全面的现况分析研究。

行NOTES保胆治疗患者术后3个月内肠道菌群的变化

目的探讨行自然腔道内镜手术(natural orifice transluminal endoscopic surgery,NOTES)保胆取石(或取息肉)治疗对胆囊良性病变患者肠道菌群的影响。方法纳入诊断为胆囊良性病变并拟行消化内镜下微创保胆治疗的患者15例,分别采集围手术期术前1周内和术后3个月内的粪便样本。利用Illumina Miseq测序平台,对细菌的16S rRNA基因V3~V4可变区进行高通量测序,并对测序结果进行生物信息学分析。结果患者术后3个月内与术前1周内肠道菌群相比,多样性显著减少,与营养代谢吸收相关的拟杆菌门显著增加,厚壁菌门/拟杆菌门(F/B)比率显著降低,肠道菌群结构仍存在明显差异,主要体现为:一些与胆汁酸代谢相关菌如脆弱拟杆菌(Bacteroides fragilis)显著增加;部分与肥胖相关的菌属如布雷德菌属(Bulleidia moorei)、长链多尔氏菌(Dorea longicatena)显著减少,部分与短链脂肪酸代谢相关菌如灵巧粪球菌(Coprococcus catus)、产气柯林斯菌(Collinsella aerofaciens)、甲酸芽殖菌(Gemmiger formicilis)、粪罗斯氏菌(Roseburia faecis)显著减少;部分有害菌如哈氏梭菌(Clostridium hathewayi)、韦荣氏球菌属(Veillonella)显著增加。结论胆囊良性疾病患者行NOTES保胆取石(或取息肉)治疗术后3个月内,肠道菌群多样性仍显著减少、胆汁酸代谢相关菌增加、短链脂肪酸产生菌减少、部分有害菌增加。总体上,肠道菌群尚未完全恢复,仍处于失调状态。

Microbial diversity and functionally distinct groups in produced water from the Daqing Oilfield,China

The microbial community structure and functionally distinct groups in three kinds of produced water samples from the shallow,mesothermic and low-salinity Daqing oil reservoir were systematically evaluated using both culture-dependent and culture-independent methods.Sequence analysis of the 16S rRNA genes indicated that the bacterial library was dominated by Acinetobacter and Arcobacter and the archaeal community was dominated by Methanosaeta and Methanolinea.Two isolated methanogens were closely related with Methanothermobacter thermautotrophicus and Methanoculleus receptaculi.The fermentative bacteria were identified as Pseudomonas,Haloanaerobium,Alcalibacter,Arcobacter,and Pannonibacter.The predominant nitrate-reducing bacteria fell within the genus Pseudomonas.The dominant members of the cultured hydrocarbon-oxidizing bacteria were phylogenetically associated with Micrococcus,Pseudomonas,and Bacillus.Enrichments of biosurfactants and biopolymer producing groups mainly yielded Pseudomonas,Bacillus,and Acenitobacter-related members.The functional groups related to polymer degradation were also affiliated with Pseudomonas and Bacillus.Results from this study provide the fresh insight into the diversity of microbial communities in Daqing petroleum reservoirs.The vast pool of functional strains retrieved in this study was presumed to include the promising strains that could be applied in microbial-enhanced oil recovery in future.

Family-level diversity of extracellular proteases of sedimentary bacteria from the South China Sea

Protease-producing bacteria and their extracellular proteases are key players in degrading organic nitrogen to drive marine nitrogen cycling and yet knowledge on both of them is still very limited. This study screened protease-producing bacteria from the South China Sea sediments and analyzed the diversity of their extracellular proteases at the family level through N-terminal amino acid sequencing. Results of the 16 S rRNA gene sequence analysis showed that all screened protease-producing bacteria belonged to the class Gammaproteobacteria and most of them were affiliated with different genera within the orders Alteromonadales and Vibrionales. The Nterminal amino acid sequence analysis for fourteen extracellular proteases from fourteen screened bacterial strains revealed that all these proteases belonged to the M4 family of metalloproteases or the S8 family of serine proteases. This study presents new details on taxa of marine sedimentary protease-producing bacteria and types of their extracellular proteases, which will help to comprehensively understand the process and mechanism of the microbial enzymatic degradation of marine sedimentary organic nitrogen.

高产铁载体菌对重金属胁迫下牧草种子萌发的影响

为研究贵州野生白三叶(Trifolium repens L.)根际高产铁载体菌TSTJ-5在重金属胁迫下对牧草种子萌发的影响,本试验对菌株进行鉴定,检测其促生特性,分别利用菌株发酵上清液、菌体和菌液,研究菌株在不同浓度的Cu^(2+)、Zn^(2+)和Pb^(2+)胁迫下对多花黑麦草和白三叶种子萌发的影响。结果表明,高产铁载体菌TSTJ-5鉴定为假单胞菌(Pseudomonas sp.),具有溶解无机磷、分泌IAA和固氮能力,多花黑麦草和白三叶种子对Zn^(2+)和Pb^(2+)均具有较强的耐性,TSTJ-5菌株在高浓度Cu^(2+)、Zn^(2+)和Pb^(2+)胁迫下能缓解重金属对供试牧草种子的毒害作用,提高种子抗逆性,促进种子发芽。研究结果可为铁载体在植物-微生物联合修复土壤重金属污染应用中提供有效的试验依据和可靠的候选菌种资源。