无蒸煮生淀粉糖化酶霉菌的选育

从23份土样中筛选出105株野生型霉菌，其中有10株具有较高的糖化生淀粉的能力，尤以A－4（Ⅱ）、C和E6 3株菌酶活力最高，分别达112562，825．1和825．1个酶活性单位；对C株菌进行紫外光诱变，从诱变后的菌株中筛选出有较大正向突变的两株菌株C（1）和C（5），与诱变前相比，C（1）菌的生淀粉糖化酶活力提高了27．3％，经生淀粉酒精发酵试验，相同条件下酒精度提高了22．4％；C(5) 的生淀粉糖化酶活力提高了12．1％，酒精度提高了5．97％。     

食品中克罗诺杆菌的分离和鉴定

利用国标方法对食品(蔬菜,熟食和豆制品)进行了克罗诺杆菌的污染情况调查及其分离菌株的鉴定;利用fus A基因对分离的克罗诺杆菌进行了遗传多样性分析,将克罗诺杆菌属的分离株鉴定到种的水平。主要取得了以下结论和认识:139份食品(蔬菜23份,熟食14份和豆制品2份)中有14份样品检出了克罗诺杆菌,检出率为35.9%。蔬菜类检出8份(34.8%),熟食制品检出4份(28.6%),2份豆制品都检出(100.0%);2对14株克罗诺杆菌分离株进行基于fus A基因的系统进行分析,结果显示这些分离株包括C.Sakazakii和C.malonaticus 2个种,其中C.sakazakii有9株,C.malonaticus有5株。     

不同假小链双歧杆菌对碳水化合物利用能力的比较研究

该研究通过生长曲线和体外发酵实验对12株假小链双歧杆菌利用17种碳水化合物的能力进行了比较探究。从整体上看，假小链双歧杆菌能在葡萄糖、乳糖、低聚半乳糖培养基中达到较高的生长量(OD₆₀₀≥0.99),在蔗糖、低聚半乳糖培养基中达到高的生长速率(代时≤150 min)。研究发现12株假小链双歧杆菌对于碳水化合物利用具有较大的差异性，其中FJSNT36M3仅能利用5种碳水化合物，而3株菌(FHNBA14M1、FGZ16I1M1、FXJWS49M21)能利用10种以上。3株菌(FGSYC12M4、FGZ16I1M1、FFJND17M1)在9种碳源培养基中的生长速率(代时)和生长量(OD₆₀₀)较高。12株假小链双歧杆菌编码的大多为降解植源性碳水化合物的糖苷水解酶，在碳水化合物利用中展现出的差异可能是因为降解和转运碳水化合物的酶具有差异性。人粪便体外发酵实验证明，假小链双歧杆菌对碳水化合物利用能力的不同与其占据肠道内丰度的潜力相关。     

基于全基因组测序的阪崎克罗诺杆菌婴幼儿食品分离株分子特征研究

目的 研究婴幼儿食品中分离的阪崎克罗诺杆菌(C.sakazakii)分子生物学特征。方法 对婴幼儿食品中C.sakazakii进行分离鉴定、药物敏感性试验和全基因组测序,利用BioNumerics软件对全基因组数据进行拼接组装,对组装基因组开展多位点序列分型(MLST)、核心基因组多位点序列分型(cgMLST)、毒力基因和耐药基因分析,并与PubMLST数据库中ST型进行比较分析。结果 本研究中分离的9株C.sakazakii共分为5个ST型,ST1和ST64型为主要型别,同时也是PubMLST数据库中C.sakazakii的主要型别。3株C.sakazakii携带mcr-9耐药基因,但药敏结果显示所有菌株对包括多粘菌素B和多粘菌素E在内的12种抗生素均敏感。除携带共同毒力基因谱外,ST1、ST64和ST458型携带脂多糖基因gtrB。cgMLST聚类分析显示,9株C.sakazakii呈高度多样性。结论 与临床分离株相关的ST1和ST64型是本研究食品分离株中的主要型别,提示C.sakazakii具有潜在的致病性,有必要对婴幼儿食品中C.sakazakii开展连续监测,为预防控制由其引起的食源性疾病提供依据。     

食品香辛料和调味品中克罗诺杆菌的分离与鉴定

利用生理生化鉴定方法和分子生物学方法对从湖南、湖北、江苏和上海等地的8个地区采集的64份干制食品香辛料和调味品样品进行了克罗诺杆菌分离与鉴定,结果从19份样品中检出了克罗诺杆菌,污染率为29.7%,其中检出率较高的样品为白胡椒粉、花椒粉和红辣椒粉,污染率分别为62.5%、50.0%和33.3%。本研究从采样的7个地区的样品中检出了克罗诺杆菌,其中检出率最高的地区为湖南永州,其次为上海市和湖北赤壁,检出率分别为50.0%、37.5%和33.3%。利用基于fus A基因序列分析的方法对克罗诺杆菌分离株进行了种的水平的鉴定,结果将本研究分离得到的克罗诺杆菌鉴定为5个种,其中9株(47.4%)被鉴定为阪崎克罗诺杆菌(C.sakazakii),4株(21.0%)为苏黎世克罗诺杆菌(C.turicensis),3株(15.8%)为都柏林克罗诺杆菌(C.dublinensis),2株(10.5%)为丙二酸盐阳性克罗诺杆菌(C.malonaticus),1株(5.3%)为尤尼沃斯克罗诺杆菌(C.universalis)。研究结果表明市售干制食品香辛料和调味品中存在克罗诺杆菌的污染,应该加强对该类食品中克罗诺杆菌的流行病学监测。     

产4-羟基-2,5-二甲基-3(2H)-呋喃酮酵母菌的分离、筛选及分子生物学鉴定

以菠萝、草莓等水果为分离源,分离、筛选利用D-果糖产香料HDMF酵母菌株,并对其高产菌株进行分子生物学鉴定。采用稀释涂布法分离酵母菌株,高效液相色谱法检测HDMF产量,26SrDNAD1/D2区序列分析及系统发育分析鉴定菌株。共分离得到46株酵母,5株可利用D-果糖产HDMF;产量较高的两株菌为:C5(6.84mg/L)、P3(10.96mg/L),分别约为已报道毕赤氏酵母属(Pichia capsulata)利用L-(+)-鼠李糖产HDMF的3倍和5倍;26S rDNA D1/D2区序列分析及系统发育分析结果显示,P3与Pichia caribbica(毕赤酵母属),C5与Hanseniaspora sp.(有孢汉逊酵母属)相似性均在99%以上,分子生物学法鉴定P3为Pichia caribbica,C5为Hanseniaspora sp.     

海洋微藻总脂含量和脂肪酸组成的测定

对14株海洋微藻(绿藻纲6株,金藻纲4株,硅藻纲3株,甲藻纲1株)中的总脂含量和脂肪酸成分进行了测定.结果表明,14株海洋微藻的总脂含量存在着明显差异,盐藻的总脂含量最高,占干重的28.71%;4株金藻的总脂含量均较高,超过干重的20%.14株海洋微藻的脂肪酸成分和含量也存在着较大的差异,绿藻中饱和脂肪酸C16:0的含量均较高;对于单不饱和脂肪酸,小球藻以C16:1(n-7)为主,盐藻以C18:1(n-7)为主,青岛大扁藻以C18:1(n-9)为主.4株金藻的PUFAs含量均较高,几乎占脂肪酸总量的1/2,并且DHA的含量较其他藻株高.3株硅藻的EPA含量最高,占27.2%～32.9%;而裸甲藻的PUFAs含量最低,仅为25.2%.     

谷类食品中克罗诺杆菌的分离与鉴定

为了解谷类食品中克罗诺杆菌(Cronobacter spp.)的污染情况。本研究采集了100份谷类食品样品,采用国家标准GB 4789.40-2010分离克罗诺杆菌,并利用基于ITS和Omp A特异基因片段的PCR鉴定方法、16S r DNA基因序列分析等方法对可疑克罗诺杆菌进行了初步的鉴定。结果发现谷类食品中克罗诺杆菌的污染率为21.0%,并分离出21株可疑克罗诺杆菌,其中17株(占总数的81.0%)被初步鉴定为阪崎克罗诺杆菌(C.sakazakii),3株(占总数的14.2%)为都柏林克罗诺杆菌(C.dublinensis),1株(占总数的4.8%)可能为尤尼沃斯克罗诺杆菌(C.universalis)或苏黎世克罗诺杆菌(C.turicensis)。研究结果表明市售谷类食品中存在食源性克罗诺杆菌的污染,应该加强谷类食品中克罗诺杆菌的流行病学监测。     

四川泡豇豆原料表皮附生乳酸菌抗生素抗性及抗性基因污染分析

以鲜豇豆为研究对象,利用生理生化特征、16S r RNA、抗生素抗性和抗性基因检测分析其表皮附生乳酸菌对氯霉素(CHL)、四环素(TET)和氨苄青霉素(AMP)的抗性与抗性基因。结果表明:从鲜豇豆表皮共分离得到182株乳酸菌,分别属于Weissella confuse(50.0%)、Weissella cibaria(15.4%)、Enterococcus sulfurous(7.1%)和Lactococcus lactis subsp.lactis(27.5%)。32株(17.6%)乳酸菌对CHL和TET有抗性,其中,6株W.confuse(3.3%)和4株L.lactis subsp.Lactis(2.1%)对CHL单一抗性,4株W.confuse(2.1%)和5株L.lactis subsp.Lactis(2.7%)对TET单一抗性,6株W.confuse(3.2%)、2株W.cibaria(1.1%)、1株E.sulfurous(0.5%)和4株L.lactis subsp.Lactis(2.1%)对CHL和TET二重抗性;编码外排泵基因efr A、efr B、nor B、nor C、nor E和sug E中,efr B的检出率最高,达31.3%,efr B和sug E的检出率最低,为3.1%。TET被检抗性基因tet(A)、tet(B)、tet(C)、tet(D)、tet(H)和tet(L)中,tet(C)的检出率最高,达90.9%,tet(B)的检出率最低,为4.5%。     

中式熟食咸鸡主要细菌的分离与初步鉴定

采用嗜冷菌选择性培养基和含盐选择性培养基对咸鸡微生物菌群进行分离筛选。根据细菌的菌落形态、革兰氏染色反应等常见特征,由嗜冷菌选择性培养基分离出6 株菌C1～C6,含盐选择性培养基分离出4 株NaCl 胁迫条件下细菌S1～S4。提取单菌落DNA,对其16S rDNA 序列进行PCR 扩增后测序,结合形态、常规生理生化特性初步鉴定为：松鼠葡萄球菌(Staphylococcus sciuri)C3,土生克雷伯氏菌(Klebsiella terrigena)C6,不动杆菌属(Acinetobacter sp.)C1、C2、C4、C5;日勾维肠杆菌(Enterobacter gergoviae)S1,表皮葡萄球菌(Staphylococcusepidermidis)S2、S3,假蕈状芽孢杆菌(Bacillus pseudomycoides)S4。     

Aquaporin in Candida: characterization of a functional water channel protein.

The Candida albicans genome database contains one ORF with homology to aquaporins, AQY1. Xenopus oocytes injected with cRNA encoding C. albicans Aqy1p displayed a coefficient of water permeability (P(f)) that was equivalent to the P(f) for oocytes injected with the cRNA of S. cerevisiae Aqy1p. In addition, as seen in Saccharomyces for Aqy1p and Aqy2p, deletion of AQY1 in C. albicans resulted in cells that were less sensitive than wild-type to osmotic shock. In Saccharomyces, aquaporin null cells also have a cell surface that is more hydrophobic. However, unlike Saccharomyces, there was no effect on the cell surface hydrophobicity, flocculation or cell aggregation in aqy1 null C. albicans cells. Perhaps as a result, there was no difference between the virulence of C. albicans wild-type and aqy1 null strains in a murine model for systemic candidiasis.     

Methods for the preparation of cell walls from potatoes

A group of new methods is described for preparing cell walls from potatoes and processed potato products. Starting from raw domestic potatoes, starch is degraded enzymatically after a very brief 100 °C gelatinisation step conducted after homogenisation to minimise the time required for heat transfer. Protein is removed by detergent and phenol extraction. This procedure (method 1) gave cell wall preparations containing <5% starch, with minimal degradation of wall polysaccharides. It did not, however, remove starch efficiently from industrial potatoes in which the starch content is much higher. A different procedure, method 2, was used in this case. In method 2 a 20 min starch gelatinisation step was used but the temperature was restricted to 70 °C and the pH to 4.0, with the aim of protecting pectins from depolymerisation. Method 2 and method 1A, which is a hybrid procedure involving the starch gelatinisation step from method 2 and other steps from method 1, gave low‐starch cell walls from industrial as well as domestic potatoes. These methods are suitable for a range of potato types and potato products and are either more efficient or more convenient than previous procedures for cell wall isolation. © 2002 Society of Chemical Industry     

THE MODE OF BINDING OF β-GLUCANS AND PENTOSANS IN BARLEY ENDOSPERM CELL WALLS

β-Glucans in barley endosperm cell walls exist as polymers of very high molecular weight (about 4 × 10⁷ daltons) containing firmly linked peptide sequences. This peptidic material is an essential part of the structure of the β-glucan complex as it exists in the cell wall. Rupture of peptide bonds by hydrazinolysis or with the proteolytic enzyme thermolysin gives β-glucans similar in size to those from short-grown green malts (about 10⁶ daltons). This suggests that proteolysis is the first step in β-glucan degradation. Large β-glucans are not all precipitated in 30% (w/v) ammonium sulphate; only 34% of the β-glucan in a hot aqueous extract of cell walls is precipitated. The amount is increased to 63% if the cell walls have been previously dehydrated. Prolonged incubation of cell wall β-glucan at 40°C, mechanical stress, chromatography lasting 8–10 h at or above 65°C, or chromatography in M sodium chloride causes some disassociation of high molecular weight β-glucan to a size of about 10⁷ daltons. Heating a solution for 1 h at 100°C does not disassociate the β-glucan. Pentosans isolated from cell walls are not covalently linked to the β-glucans and can be separated from them by molecular sieve chromatography. They have a higher xylose/arabinose ratio than previously reported for barley pentosans. The pentosan molecules extracted by water are smaller (10⁶ daltons) than those extracted by alkali (5 × 10⁶ daltons). Little difference was observed in the chemical or physical properties of cell wall materials of barley cultivars of different malting qualities.     

Ferulic Acid Dehydrodimers in the Cell Walls of Beta vulgaris and their Possible Role in Texture

Sugarbeet, a form of Beta vulgaris var vulgaris, fails to soften completely after heating at 100°C for several hours. This is due to thermal stability of the cell–wall polymers involved in cell–cell adhesion. In contrast, beetroot softens within 25–30 min due to a relatively rapid increase in the ability of the cells to separate. Information concerning the cell–wall polymers responsible for cell–cell adhesion was obtained by subjecting sugarbeet and beetroot tissues to a range of chemical and biochemical treatments designed to cleave cell–wall chemical bonds selectively. Treatment of sugarbeet tissues with chelating agents, weak base (Na₂CO₃, 0·05 M ) or a purified, specific endoxylanase did not facilitate vortex-induced cell separation. However, this could be induced after extraction in dilute, cold alkali (0·05–0·1 M KOH) or dilute, hot acid (0·1 M TFA, 100°C). Tissues from beetroot behaved similarly. Furthermore, the cell walls of sugarbeet and beetroot were similar in yield and neutral carbohydrate composition; the cell–wall-galacturonic acid content of beetroot was 50% higher as compared with sugarbeet. They were also rich in ferulic acid (FA) and its derivatives (6–7 mg g^-1 CWM), and exhibited pH-dependent autofluorescence which disappeared during alkali-induced cell separation. In sugarbeet, over 20% of the FA was in dimer form. In beetroot, however, the value was only 10%. The main FA dimers were 8-O-4′DiFA and 8,5′DiFA (benzofuran form). The results indicate that the degree of thermal stability of cell–cell adhesion and, therefore, texture in Beta vulgaris tissues is related to the degree of FA-cross linking between pectic polysaccharides. © 1997 SCI.     

Behaviours of log phase cultures of eight strains of Escherichia coli incubated at temperatures of 2, 6, 8 and 10 degrees C

The behaviours of cold-adapted, log-phase cultures of eight strains of Escherichia coli incubated at 2, 6, 8 and 10 degrees C for 10 days were examined by determining absorbance at 600 nm (A(600)), viable counts and cell size distribution as indicated by forward angle light scattering (FALS) values, obtained for samples collected each day from each culture. Cell lengths were determined from photomicrographs of samples for which the flow cytometry data indicated the mean cell lengths were maximal or minimal for each culture. At 2 degrees C, A(600) values for all strains and viable counts for some changed little, while viable counts for other strains declined progressively by >1 log unit. At 6 degrees C, A(600) values for most strains increased at progressively declining rates and then remained constant while viable counts increased to reach maximum values before maximum A(600) values were attained, and then declined. At 8 degrees C, the behaviours of most strains were similar to the behaviour at 6 degrees C. At 10 degrees C, seven of the strains grew exponentially, but for most of these the growth rate determined from A(600) values differed from that determined from viable count data. Mean FALS values for cultures incubated at 6, 8, or 10 degrees C showed various patterns of increase and decrease, indicating fluctuations in cell lengths. For all strains, the minimum cell length was <3 microm, but the maximum cell lengths ranged from <20 to >140 microm. The findings suggest that the formation of elongated cells or filaments is usual behaviour for E. coli growing at temperatures approaching or below the minimum for sustained growth.     

Role of Sho1p adaptor in the pseudohyphal development,drugs sensitivity,osmotolerance and oxidant stress adaptation in the opportunistic yeast Candida lusitaniae

In yeast, external signals such as high osmolarity or oxidant conditions activate the high osmolarity glycerol (HOG) mitogen‐activated protein kinase (MAPK) cascade pathway, which consists of two upstream branches, i.e. Sho1p and Sln1p and common downstream elements, including the Pbs2p MAPK kinase and the Hog1p MAPK. We recently showed that the Candida lusitaniae SLN1 gene, potentially encoding a histidine kinase receptor, is crucial for oxidative stress adaptation when the fungus grows as budding yeast and during the early steps of pseudohyphal development. In the current study, we characterized the SHO1 gene of this opportunistic fungus. Complete loss of SHO1 function causes profound defects in pseudohyphal differentiation, especially in high osmolarity and oxidative stress conditions, suggesting a crucial role of SHO1 in the pseudohyphae morphogenetic transitions. Moreover, when grown as budding yeast, the sho1Δ mutant revealed a sensitivity to compounds that interfere with the cell wall assembly, pointing to a potential role of Sho1p in cell wall biogenesis. However, the sho1Δ mutant does not display evident cell‐wall architecture modifications, such as aggregation phenotypes. Although not hypersusceptible to antifungals of clinical relevance, the sho1Δ mutants are susceptible to the filamentous fungi‐specific antifungals dicarboximides and phenylpyrroles. Finally, our findings highlight some significant phenotypic differences when the C. lusitaniae sho1Δ mutant is compared with the corresponding mutants described in Saccharomyces cerevisiae, Candida albicans and Aspergillus fumigatus. The GeneBank Accession No. for C. lusitaniae SHO1 gene is EU797514. Copyright © 2008 John Wiley & Sons, Ltd.     

Inhibition of yeast‐to‐filamentous growth transitions in Candida albicans by a small molecule inducer of mammalian apoptosis

The opportunistic fungal pathogen of humans Candida albicans is able to grow in different morphological forms such as round or oval yeasts and filamentous hyphae and pseudohyphae. Morphogenesis, the ability to switch between the yeast and filamentous growth forms, is important for adapting to new microenvironments in the human host and for pathogenesis. The molecular pathways governing morphogenesis are complex and incompletely understood. Previously, we identified several small organic molecules that specifically inhibit the initiation of hyphal growth in C. albicans without affecting cell viability or budded growth. One molecule from that screen is known to induce apoptosis in mammalian cells. In this study, we have screened additional inducers of mammalian apoptosis and identified BH3I‐1, as well as several structural derivatives of BH3I‐1, that act as specific inhibitors of morphogenesis under a variety of environmental conditions. Chemical epistasis experiments suggest that BH3I‐1 acts downstream of the hypha‐specific gene regulators Rfg1, Nrg1 and Ume6.     

UPTAKE AND TURNOVER OF 14C GLUCOSE BY YEAST DURING WORT FERMENTATIONS

The incorporation of randomly labelled ¹⁴C glucose, or substances derived from it, into various cell components was followed during a brewery type fermentation, using a yeast polysaccharide fractionation technique in conjunction with liquid scintillation. The labelled glucose, when added to wort, was assimilated by brewer's yeast, most of it being fermented to ¹⁴C ethanol. A small but significant amount of the ¹⁴C glucose, or its metabolites, was incorporated into the polysaccharide fractions of the yeast. Employment of a simple “swop-over” technique has shown that in two of these fractions, the low molecular weight acid-soluble material and the mannan, there was a substantial turnover, reflecting respectively the transient metabolic status of the former and the special role of mannan in the structure of the outer layer of the cell wall. Glucan, as would be expected from its function as the principal structural component of the cell wall complex, was completely stable. Glycogen was also stable, and showed no evidence of turnover, even during the later stages of the fermentation. Hence it is unlikely that it could function as an energy reserve in this strain (N.C.Y.C. 240) during primary fermentation of brewer's wort.     

The solubilisation and hydrolysis of spinach cell wall polysaccharides in gastric and pancreatic fluids

The aim of this work was to investigate the fate, in the upper gut of a monogastric animal, of polymers bound within plant cell walls. Uniformly and specifically ¹⁴C-labelled spinach cell walls were incubated in artificial body fluids with and without pepsin or pancreatin. In the absence of enzymes, artificial pancreatic juice (pH 8.8) at 37°C hydrolysed the methyl ester groups of wall-bound pectins [half-life (t^1/2) 25 h]; the O-acetyl ester groups of cell wall polysaccharides were much more stable (t ^1/2 84 h). In contrast, artificial gastric juice (pH 1.85) hydrolysed wall-bound acetyl groups more rapidly (t ^1/2 ～ 24 h) than methyl ester groups (t ^1/2 ～ 350 h). Thus, a proportion of the methyl and acetyl groups of plant cell wall polymers will be released in the upper gut as methanol and acetic acid, raising the question of whether these groups should be included within the definition of dietary fibre. The artificial body fluids also caused limited solubilisation of wall polymers but no hydrolysis to mono- or oligosaccharides. Neither pepsin nor pancreatin promoted the hydrolysis of methyl ester or acetyl groups. The small amounts of [¹⁴C]protein present in the cell wall preparations were hydrolysed by pepsin or pancreatin to yield amino acids and oligopeptides; however, the major polysaccharides of spinach cell walls were neither degraded to low-molecular-weight products nor solubilised by these enzymes.     

Mutagenicity and Safety Evaluation of Water Extract of Coriander sativum Leaves

ABSTRACT:  Coriander has been used as a spice and medicinal plant for centuries. Several studies have described its biological properties and some reports have indicated its pharmacological actions in some human pathology. However, data on its toxicity and metabolism are limited or null, and no research has been conducted with mammalian cells. The purpose of this study was to evaluate the mutagenicity and safety of  Coriandrum sativum  extract. The mutagenic effects of  C. sativum  extract were evaluated by Ames test. Mutagenicity was present when the  C. sativum  extract was used in high concentrations in both tested strains ( Salmonella typhimurium  TA97 and TA102). Our research showed that  C. sativum  extract reduced the cell survival of human cell lines (WRL-68 and 293Q cells) by inducing apoptosis and necrosis in the cases where extract concentration was the highest. The  C. sativum  extract altered the cell cycle; it increased the G1 phase of hepatic cells and reduced the G2+M phase in both cell lines in a dose-response manner. These results showed correlation with a reduction in the mitotic index. The extract also induced severe malformations during embryonic development. Exposure of chicken embryos to the  C. sativum  extract resulted in a dose-dependent increase of anomalies. Present results show that  C. sativum  extract reduced the axial skeleton and affected the neural tube, the somites, the cardiovascular structures, and the eye. According to the present results, the  C. sativum  aqueous extract cannot be considered safe. These results indicate that some significant adverse effects of  C. sativum  extract could be observed  in vivo .