不同酿酒酵母(Schromycese cerovisea)对黄酒挥发性香气物质的影响

研究不同酵母菌株对黄酒挥发性香气物质形成的影响,采用4种不同酿酒酵母(黄酒活性干酵母、工业生产用黄酒酵母HJ-1,HJ-2、耐高温活性干酵母(NGW))菌株进行实验室黄酒酿造试验,采用固相微萃取-气质联用技术测定了发酵后四种黄酒中挥发性香气物质含量,检测出与酵母相关的27种挥发性成分.研究结果表明不同酵母菌株酿制黄酒样品挥发性香气物质存在明显的差别.其中,HJ-2菌株β-苯乙醇,总酯含量较高,香气较为纯正;NGW活性干酵母挥发性酸含量较高;黄酒活性干酵母挥发性酯含量较低.本研究发现通过选用不同酵母菌株能够有效的调节黄酒生产风味物质的形成.     

AFLP技术对发酵酸面团中乳酸菌多态性的研究

乳酸菌是酸面团发酵的主要细菌,它对面团的质量、营养有非常重要的作用,利用AFLP技术对分离自酸面团中的20株乳酸菌进行了研究,以期了解其中乳酸菌的多态性及其分型。研究优化并确定了AFLP技术的各种实验条件,然后利用该技术对乳酸菌的多态性进行了研究,并采用聚类分析软件ProBiosys 1.0对实验结果进行了分析。     

传统发酵肉制品中微生物菌群对风味形成的研究进展

我国传统发酵肉制品种类丰富、风味独特。本文主要介绍参与肉制品发酵的微生物,从蛋白质、脂质和碳水化合物代谢途径的角度概述微生物对发酵肉制品呈香物质形成的作用机制,以及发酵过程中微生物的演替与风味变化的关系。     

两种温度条件下早熟桃果实中挥发性物质成分分析

采用热脱附-气相色谱-质谱(CTC-GC-MS)分析技术测定了两种温度(4和20℃)条件保存下早熟桃品种京春(早生黄金实生)果肉和果核中挥发性物质成分.定性分析显示有24种化合物,主要是醛、酯、酸、醇、烃、萜、抗氧化物质等,其中23种在常温下的果肉中测得,21种在常温下的果核中测得,相对含量较高的是乙酸乙酯.在低温条件下,果肉和果核中分别测得21种和16种,和常温下相比,大部分物质含量都较低,而醛类物质(3-甲基丁醛除外)则几乎相反,尤其是2-己烯醛只在低温下测到.官能评定结果显示,经低温保存70h后的风味比常温下保存的要好.     

狐粪青霉挥发性物质的抑菌活性及成分分析

采用对扣法测定狐粪青霉XY180挥发性物质对植物病原真菌的抑制作用,并采用气相色谱—质谱联用技术(GC-MS)分析狐粪青霉挥发性物质的化学成分。结果表明:狐粪青霉挥发物对植物病原真菌的菌丝生长具有一定的抑制作用,从狐粪青霉菌体的乙醚萃取液中共分离到26个组分,鉴定了其中的13个组分。     

葡萄酒中重要挥发性硫化物的代谢及基因调控

葡萄酒中的挥发性硫化物是由酿酒微生物在葡萄酒发酵过程中代谢所产生的,主要包括硫化氢、硫醇、硫醚、硫醇酯、含硫杂醇油及杂环化合物等,它们对葡萄酒的风味会产生重要影响。本综述介绍了葡萄酒中重要的挥发性硫化物的主要代谢途径及相关基因的调控机制,并提出酿酒微生物的相关研究是提高优良风味物质含量,同时抑制不良风味产生的有效途径。     

褐飞虱遇险释放挥发性物质的提取及成分分析

利用Y型嗅觉仪测定不同试验条件下褐飞虱Nilaparvata lugens(Stl)对同类昆虫遭遇草间小黑蛛Erigonidium graminicolum Sundvall捕食时挥发性物质的行为反应,并利用固相微萃取、气相色谱与质谱技术分离鉴定挥发性物质。目的明确褐飞虱遇险释放挥发性物质的最佳提取条件,并分析该挥发性物质的成分。结果表明,用乙酸乙酯、甲醇和正己烷分别提取"褐飞虱2³龄若虫+草间小黑蛛成蛛"共存体释放的挥发性物质,发现乙酸乙酯提取物能引起褐飞虱极显著的逃避行为。用不同褐飞虱虫量(100、300、600头/500 mL瓶)、不同提取时间(1、3、6 h)和不同溶剂温度(15、25、35℃)分别提取"褐飞虱23龄若虫+草间小黑蛛成蛛"共存体释放的挥发性物质,发现乙酸乙酯提取物能引起褐飞虱极显著的逃避行为。用不同褐飞虱虫量(100、300、600头/500 mL瓶)、不同提取时间(1、3、6 h)和不同溶剂温度(15、25、35℃)分别提取"褐飞虱2³龄若虫+草间小黑蛛成蛛"共存体释放的挥发性物质,发现3003龄若虫+草间小黑蛛成蛛"共存体释放的挥发性物质,发现300⁶00头、3600头、3⁶ h和25℃下的提取物能引起褐飞虱极显著的逃避行为,明确了褐飞虱遇险释放挥发性物质的最佳提取条件。利用固相微萃取法分别萃取"褐飞虱26 h和25℃下的提取物能引起褐飞虱极显著的逃避行为,明确了褐飞虱遇险释放挥发性物质的最佳提取条件。利用固相微萃取法分别萃取"褐飞虱2³龄若虫"释放的挥发性物质和"褐飞虱23龄若虫"释放的挥发性物质和"褐飞虱2³龄若虫+草间小黑蛛成蛛"共存体释放的挥发性物质。气相色谱分析表明,保留时间16 min、21.5 min时,"褐飞虱"与"褐飞虱+草间小黑蛛"共存体释放的挥发物均出现新峰;保留时间10.94 min时,仅"褐飞虱+草间小黑蛛"共存体释放的挥发物出现新峰。推测保留时间10.94 min时出现的峰为褐飞虱被草间小黑蛛捕食时释放的示警挥发物。质谱分析进一步表明,这种挥发物具有与(E)-2-己烯醛相类似的化学结构,但其实际结构还需深入研究。     

一株木霉菌挥发性物质的抑菌活性测定及成分分析

目的：测定木霉菌XYT-12菌株的挥发性物质对植物病原真菌的抑制活性,并分析其挥发性物质的化学成分。方法：抑菌活性测定采用对扣法,化学成分分析采用气相色谱-质谱联用法（GC-MS）。结果：木霉菌XYT-12的挥发性物质对植物病原真菌有一定的抑制活性,以对番茄灰霉病菌的抑制作用最强,达到61.78%;木霉菌挥发性物质的主要成分为6-戊基-2H-吡喃-2-酮（6PP）,在菌丝和PDB培养液挥发物中的相对含量分别为90.346%和88.729%。     

兴安杜鹃叶中挥发性成分的GC-MS分析

采用水蒸气蒸馏法对兴安杜鹃叶中的挥发性成分进行提取,并运用气相色谱—质谱联用技术(GC-MS)对其挥发性成分进行了系统的分离和鉴定。从兴安杜鹃叶中共鉴定出54种挥发性成分,占总馏出成分的97.84%。兴安杜鹃叶主要挥发性成分为桉叶醇(eduesmol),相对含量10.95%;β-愈创木烯(β-guaiene),相对含量10.21%;长叶醛(longifolenaldehyde),相对含量7.88%;1,5,9,9-四甲基-1,4,7-环十一碳三烯(1,5,9,9-tetramethyl-1,4,7-cy-cloundecatriene),相对含量7.80%;杜鹃酮(germacrone),相对含量5.91%;(-)-葎草烯环氧化物Ⅱ((-)-HumuleneepoxideⅡ),相对含量5.52%;2-庚基-1,3-二氧戊环(2-heptyl-1,3-dioxolane),相对含量4.99%;石竹烯(caryo-phyllene),相对含量3.70%;(+)-γ-古芸烯((+)-γ-gurjunene),相对含量3.44%。     

新疆地区酸马奶中酵母菌的鉴定及其生物多样性分析

从新疆少数民族牧民家庭采集的28份传统工艺酿造酸马奶样品中分离出87株酵母菌,并对其进行了生理生化鉴定、分子生物学鉴定和生物多样性分析。生化试验结果表明,新疆地区酸马奶中的酵母菌为Saccharomyces unisporus(占总分离株的48.3%),Kluyveromyces marxianus(27.6%),Pichia membranaefaciens(15.0%)和Saccharomyces cerevisiae(9.2%)。选取其中的6株酵母菌和1株参考菌株,进行大亚基(26S)rDNA D1/D2区域(600bp左右)碱基序列分析,并通过GenBank进行同源序列搜索以确定各菌株的归属,进一步验证生理生化方法的正确性。从得到的结果中可以看出,S.unisporus和K.marxianus为新疆地区酸马奶中的优势菌。     

Bacterial population in traditional sourdough evaluated by molecular methods

AIMS: To study the microbial communities in artisanal sourdoughs, manufactured by traditional procedure in different areas of Sicily, and to evaluate the lactic acid bacteria (LAB) population by classical and culture-independent approaches. METHODS AND RESULTS: Forty-five LAB isolates were identified both by phenotypic and molecular methods. The restriction fragment length polymorphism and 16S ribosomal DNA gene sequencing gave evidence of a variety of species with the dominance of Lactobacillus sanfranciscensis and Lactobacillus pentosus, in all sourdoughs tested. Culture-independent method, such as denaturing gradient gel electrophoresis (DGGE) of the V6-V8 regions of the 16S rDNA, was applied for microbial community fingerprint. The DGGE profiles revealed the dominance of L. sanfranciscensis species. In addition, Lactobacillus-specific primers were used to amplify the V1-V3 regions of the 16S rDNA. DGGE profiles flourished the dominance of L. sanfranciscensis and Lactobacillus fermentum in the traditional sourdoughs, and revealed that the closely related species Lactobacillus kimchii and Lactobacillus alimentarius were not discriminated. CONCLUSIONS: Lactobacillus-specific PCR-DGGE analysis is a rapid tool for rapid detection of Lactobacillus species in artisanal sourdough. SIGNIFICANCE AND IMPACT OF THE STUDY: This study reports a characterization of Lactobacillus isolates from artisanal sourdoughs and highlights the value of DGGE approach to detect uncultivable Lactobacillus species.     

Microbial diversity in natural environments: focusing on fundamental questions

Interactions with Gijs Kuenen and other Dutch scientists have led my lab to fundamental insights into the composition, structure and function of a hot spring cyanobacterial mat community that should influence our thinking about all microbial communities. By focusing on the distribution of molecular sequence variants of predominant mat phototrophs, we have discovered that small-scale sequence variation can be ecologically meaningful. By applying novel cultivation approaches, we have been able to obtain genetically relevant community members and thus to test the hypothesis that closely related sequence variants arose via adaptive evolutionary radiation. By applying the analytical tools of organic geochemistry we have gained insight into the metabolisms of major phototrophic members of the mat community as well as interactions between phototrophic guilds. These observations challenge traditional paradigms about prokaryotic species and cause us to consider evolutionary ecology theory as we develop genome-based methods for high-resolution analysis of the species-like fundamental units comprising microbial communities, and for investigating how such units coordinate the physiological activities within guilds of the community.     

Genotypic and phenotypic diversity of Lactobacillus rossiae strains isolated from sourdough

AIM: To characterize the genetic and phenotypic diversity of 33 strains of Lactobacillus rossiae. METHODS AND RESULTS: Genotypic identification was carried out by partial 16S rRNA gene sequence analysis. Genetic diversity was evaluated by RAPD-PCR analysis. Phenotypic diversity was evaluated through fermentative profile by Biolog system, proteinase and peptidase activities using synthetic substrates, and acidification capacity and amino acid profile during sourdough fermentation. The genetic analyses excluded clonal relatedness among the strains used. A large phenotypic diversity was found. It mainly concerned the capacity to use carbon sources available in sourdough during fermentation, the quotient of fermentation and the peptidase activities, especially towards proline containing synthetic substrates. The free amino acid profiles differed either for the total concentration or for the type of amino acids. With a few exceptions, proteinase activity towards wheat albumins and globulins was weak. CONCLUSIONS: Overall, no relationships between genetic and physiological analyses were found, and the strains examined showed a marked genetic and phenotypic heterogeneity. L. rossiae strains had interesting properties for application in sourdough fermentation. Although some strains combined several technological traits, the association of more strains seemed to be a requisite to get optimal sourdough characteristics. SIGNIFICANCE AND IMPACT OF THE STUDY: It represents the first characterization of the diversity within the L. rossiae species. Besides, it may represent an example of computerized analysis of genotypic and phenotypic information to select strains for improving sourdough characteristics.     

Microbial molecular diversity: Past and present Thom Award lecture

Journal of Industrial Microbiology &; Biotechnology -     

Microbial diversity of soil from two hot springs in Uttaranchal Himalaya

Soil samples collected from two hot springs, Soldhar and Ringigad, both located in the Garhwal region of Uttaranchal Himalaya were analysed for their physical, chemical and microbial components. The alkaline pH, total absence of carbon and nitrogen, and high temperature were features common to soil samples from both sites. The Soldhar samples contained higher amounts of Cu, Fe and Mn. Ringigad soil was devoid of Cu, but had much higher phosphate. While the optimum incubation temperature for isolating the maximum microbial counts from soil samples from the two sites was 50 degrees C, microbial growth in broth was also observed when incubated at 80 degrees C. Microscopic examination revealed three types of microbial populations, i.e., bacteria, yeast and filamentous organisms. The soil samples were found to be dominated by spore forming rods. Out of 58 aerobic isolates, 53 were gram positive bacilli. Gram positive anaerobic oval rods were also observed up to 60 degrees C. Soil dilution plates revealed the presence of antagonistic and phosphate solubilizing populations.     

盐碱地微生物类群的多样性

土壤是微生物的大本营,由于土壤理化性质的不同,与环境相适应的土壤微生物种类也各不相同。土壤盐碱化是一个世界性的难题,在我国主要分布在淮河以北、西北及新疆、青藏高原等内陆干旱、半干旱地区的河流冲积平原、盆地和湖泊沼泽地区。     

气调包装生鲜冷却牛肉贮藏中微生物多样性分析

【目的】分析普通包装和气调包装(65%O2和35%CO2)生鲜冷却牛肉在贮藏(4°C)过程中的微生物多样性。【方法】通过16S rDNA V3区PCR-DGGE(变性梯度凝胶电泳)方法和16S rDNA克隆分析法研究生鲜冷却牛肉中微生物菌落结构及菌相变化规律。【结果】初始菌相主要有嗜冷杆菌属(Psychrobacter)和假单胞菌属(Pseudomonas)。贮藏过程中,普通包装和气调包装生鲜冷却牛肉中优势菌均为Brochothrix和Pseudomonas。气调包装冷却牛肉中细菌种类较少,两种包装生鲜牛肉在贮藏前期菌相变化明显。【结论】不同包装冷却牛肉中微生物菌落结构有较大差异,气调包装中CO2对Pseudomonas等细菌起到了一定的抑制作用。     

宏蛋白质组学——研究微生物群落基因表达的新技术

宏蛋白质组学是应用蛋白质组学技术对微生物群落进行研究的一项新技术,其定义为在特定的时间对微生物群落的所有蛋白质组成进行大规模鉴定。通过对宏蛋白质组学的研究策略、进展情况的综述、介绍,展望了宏蛋白组学在研究微生物群落基因表达中的应用前景。     

Microbial community composition and its role in volatile compound formation during the spontaneous fermentation of ice wine made from Vidal grapes

Vidal grape grown in Ili, Xinjiang Autonomous Region, is one of few grapes used to ferment ice wine in China. Microbial community structure and volatile composition during the spontaneous fermentation of ice wine made from Vidal grapes in Ili were investigated using amplicon sequencing technology and headspace solid-phase microextraction/gas chromatography-mass spectrometer technologies. Among bacterial genera, Sphingobium, Pseudomonas and Sphingomonas gradually decreased, while Lactobacillus and Streptococcus increased during the spontaneous fermentation process. As regards fungi, the relative abundance of Vishniacozymaand Cladosporium reduced, but Hanseniaspora sharply raised. Additionally, correlations between microbes and volatile compounds were constructed based on multivariate data analysis. The results revealed that the functional core microbiota (mainly composed of eight bacterial genera and nine fungal genera) during ice wine fermentation showed considerable correlations with the formation of twenty-four volatile compounds in ice wine made from Vidal grapes. For example, Saccharomyces was positively correlated with ethanol, ethyl acetate and isoamylol; Hanseniaspora and Candidawere negatively correlated with hexanol; and Lactobacillus and Streptococcus were positively correlated with 2,3-butanediol, ethanol, ethyl acetate, isoamylol and isoamyl acetate. This studyprovides a reference for understanding the process of ice wine fermentation and improving the quality of ice wine made from Vidal grapes.     

Microbial diversity and community structure in Fynbos soil

The Fynbos biome in South Africa is renowned for its high plant diversity and the conservation of this area is particularly important for the region. This is especially true in the case of endangered vegetation types on the lowlands such as Sand Fynbos, of which only small fragments remain. The question is thus whether the diversity of the above‐ground flora is mirrored in the below‐ground microbial communities. In order to determine the relationship of the above‐ and below‐ground communities, the soil community composition of both fungal and bacterial groups in Sand Fynbos was characterized over space and time. A molecular approach was used based on the isolation of total soil genomic DNA and automated ribosomal intergenic spacer analysis of bacterial and fungal communities. Soil from four different sites was compared to resolve the microbial diversity of eubacterial and fungal groups on a local (alpha diversity) scale as well as a landscape scale (beta diversity). The community structures from different sites were compared and found to exhibit strong spatial patterns which remained stable over time. The plant community data were compared with the fungal and the bacterial communities. We concluded that the microbial communities in the Sand Fynbos are highly diverse and closely linked to the above‐ground floral communities.