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.

Identification of the Electricity-Producing Bacteria in Wastewater for Microbial Fuel Cells （MFCs）

A microbial fuel cell （MFC） is a device that converts chemical energy to electrical energy during substrate oxidation by microorganisms. The characterization and identification of these microbial communities will allow better control of this electricity generation with simultaneous removal of carbon and nitrogen. This study aims to investigate the role of natural bacteria in electricity generation by studying three different sources of wastewater： the raw wastewater （RW）, wastewater from an aeration tank （AEW） and returned activated sludge （RAS） from an activated sludge treatment plant. The result showed that after the MFC treatment, the number of bacterial strains was reduced from twenty strains to eight strains. Microscopic observation further showed that fifteen isolate before the treatment were gram-positive, and five were gram-negative whereas all isolates after the treatment were gram-positive rods or cocci The four strains isolated from the RAS inoculums, β-Comamonas sp., γ-Enterobacter sp., Bacillus cereus sp. and Clostridium sp. produced the highest power density of 67.57 mW/m^2 which made them potential candidates for electrochemically active bacteria in MFCs. However, the level of chemical oxygen demand （COD） removal was 20% and the total kjeldahl nitrogen （TKN） removal was 66.7%. Key words：

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.

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。

己酸菌发酵液酯化合成己酸乙酯的研究

己酸乙酯是浓香白酒的特征香气成分,其含量的多少决定着浓香型白酒的品质。本研究对己酸菌发酵液酯化合成己酸乙酯的最佳条件进行探究,研究了不同条件下的酯化pH、不同酸调节pH以及乙醇、己酸浓度对己酸菌发酵液中己酸乙酯转化率的影响。结果表明,pH在3~4时己酸乙酯转化率较高,用乳酸调节p H效果最优,增加酯化体系中乙醇、己酸浓度均有利于提高己酸乙酯的转化率;使用己酸含量为18.86 g/L的浓缩己酸菌液,加入30%的无水乙醇,0.15%的酯化酶,用乳酸调节pH至4,34℃酯化24 h,己酸乙酯含量达到8962.99 mg/L,转化率为49.77%。

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。

酸汤中高产酸细菌的分离筛选及其特性研究

目的对酸汤中分离筛选的高产酸细菌进行鉴定,并研究其生物学特性。方法从白酸汤和红酸汤中分离出的细菌,通过16S rDNA基因序列分析进行分子生物学鉴定,并研究其产酸特性、生理生化特性、耐酸碱和耐盐能力,同时用牛津杯法以抑菌圈为指标,探究其抑制致病菌性能。结果筛选出4株高产酸乳酸菌和1株产酸醋杆菌,其中RS-5为甘草乳杆菌(Liquorilactobacillus nagelii),ST15-2和RS-8为布氏乳杆菌(Lentilactobacillus buchneri),ST20为发酵粘液乳杆菌(Limosilactobacillus fermentum),ST19为产液葡糖酸醋杆菌(Gluconacetobacter liquefaciens);RS-8、ST15-2、ST20和RS-5具有较高的产酸能力,产总酸均超过(103.54±6.19)g/L,RS-8产总酸量达到(159.12±12.24)g/L,经高效液相色谱法测定ST20、RS-5和ST15-2产乳酸较高,分别是10.21、9.76和7.11 mg/mL,RS-8和RS-5产柠檬酸较高,分别为4.87 mg/mL和3.93 mg/mL;RS-8、ST15-2和ST20具有较好的耐酸性、耐碱性和耐盐性;RS-5和ST20对大肠杆菌有显著抑制作用,ST15-2对金黄色葡萄球菌有显著抑制作用。结论RS-8、ST15-2、ST20和RS-5菌株高产酸且具有较好的耐酸碱和耐盐性能,有抑致病菌作用,具有一定工业化应用前景。

CO_(2)压裂页岩油产出水中腐蚀性细菌特征及菌群多样性

采用水力压裂的页岩气田整个生产周期内的产出水普遍含大量硫酸盐还原菌(sulfate-reducing bacteria,SRB)、腐生菌(total general bacteria,TGB)和铁细菌(iron bacteria,IB)腐蚀性细菌。采用CO_(2)与水力压裂交替的CO_(2)压裂技术是现阶段页岩油开发最有前景的技术之一,页岩油产出水中SRB、TGB和IB细菌特征及菌群的多样性研究鲜有报道。采用绝迹稀释法和高通量测序技术研究了某页岩油田配置压裂液的河水、压裂液、投产0.67~76 d产出水中SRB、TGB和IB腐蚀性细菌变化规律、腐蚀性细菌对CO_(2)和井下高温环境的适应性,及细菌群落多样性的变化特征。结果表明:页岩油环境的SRB、TGB及IB细菌主要在压裂及生产初期存在(10~3~10~7个/mL),在投产47 d后,细菌含量明显降低。SRB、TGB及IB对压裂期间注入的CO_(2)的敏感性不同,CO_(2)抑制SRB、TGB的生长,促进IB的生长。在150℃,2 MPa环境中暴露10 h后,SRB、TGB和IB细菌的死亡率达99.9%。投产1 d内的产出水中的细菌主要为压裂过程引入的外源细菌。随投产时间延长,压裂过程引入的外源细菌对地层微生物菌群的影响有所降低,且产出水的细菌多样性显著增加。投产0.67 d和1 d产出水的Shannon指数分别为2.4和2.2;投产47 d和76 d后,Shannon指数增加至7.7和7.4。细菌群落结构随投产时间发生了显著变化,压裂液及投产后0.67~76 d的产出水中变形菌门(20%~97%)为优势类群;投产47 d及76 d的产出水中的厚壁菌门、酸杆菌门、放线菌门、拟杆菌门、绿弯菌门的相对丰度较高。页岩油井产出水中还存在潜在石油类降解菌芽孢杆菌纲、假单胞菌属、嗜冷杆菌属、海杆菌属等。

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。

Investigation of the relationship between cell surface hydrophobicity and demulsifying capability of biodemulsifier-producing bacteria

BACKGROUND： Cell surface hydrophobicity （CSH） is one of the key physicochemical features of biodemulsifier-producing bacteria that influence their demulsification capability maintenance in petroleum contaminated environments. METHODS： In present study, biodemulsifier-producing bacteria were isolated from petroleum contaminated environments using different isolation media and the correlation between their CSH and demulsifying ability was investigated. The demutsifying ability of isolates was measured through demulsification tests on water in kerosene emulsions. The microbial adhesion to the hydrocarbon （MATH） assay was used to denote their CSH. RESULTS： The evaluation of CSH showed that majority of biodemulsifier producing bacteria have high CSH which indicating a positive correlation between CSH and demulsifying capability. CONCLUSIONS： According to these results it can be concluded that CSH can be used as an indicator for assessment of biodemulsifier-producing bacteria and screening of new isolates for their biodemulsifier production.

外源Ca^(2+)对两种产脲酶细菌修复Cd-As复合污染水稻土的影响

微生物诱导碳酸盐沉淀(Microbially induced carbonate precipitation,MICP)技术已被广泛应用于土壤重金属污染修复。为促进MICP过程,提高土壤修复效果,以Cd-As复合污染的水稻土为研究对象,利用巴氏八叠球菌(Octococcus pasteurii)和蜡样芽孢杆菌(Bacillus cereus)两种产脲酶细菌,分析比较了外源添加氯化钙(CaCl2)对两种菌株固定土壤中Cd、As效果的影响,并对修复后土壤理化性质、酶活性及微生物多样性的变化进行了检测。结果表明:两种菌株均能固定土壤Cd、As,其中,蜡样芽孢杆菌对土壤Cd、As的固定效果更佳,与巴氏八叠球菌处理相比,蜡样芽孢杆菌处理下土壤有效态Cd、As含量分别降低了16.7%、11.1%;添加外源Ca^(2+)后,在两种细菌处理下有效态Cd、As含量均发生显著变化,分别降低了17.3%~22.2%、16.8%~26.7%,可见Ca^(2+)的添加能有效促进MICP过程,促进对Cd、As的固定。此外,与未添加Ca^(2+)处理相比,添加Ca^(2+)后,两种细菌处理下显著提高了土壤脲酶活性(52.6%~113.3%)、蔗糖酶活性(13.1%~28.9%)、碱解氮含量(3.4%~25.5%)、速效钾含量(2.1%~34.1%)以及微生物多样性,表明外源Ca^(2+)可有效提高土壤肥力及土壤生态功能。综上,基于MICP作用,可通过添加外源Ca^(2+)来增强产脲酶细菌对Cd-As复合污染土壤的修复效果,其中,蜡样芽孢杆菌修复效果更佳。

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。