微波消解-离子色谱法测定枸杞多糖的含量及组成

目的 建立微波消解-离子色谱法测定枸杞多糖含量及组成的方法。方法 分别考察了三氟乙酸浓度、微波消解温度及微波消解时间对枸杞多糖消解效率的影响,优化了离子色谱法检测枸杞多糖的色谱条件,并对所建立的方法进行方法学评价。结果 枸杞多糖最佳消解条件为温度120℃、时间20 min、三氟乙酸浓度3 mol/L;经方法学评价, 9种单糖和2种糖醛酸均具有良好的线性关系,相关系数均大于0.98;精密度相对标准偏差小于3.00%,检出限和定量限良好。通过对枸杞中单糖组成的分析,表明在枸杞中葡萄糖、木糖、半乳糖、甘露糖、阿拉伯糖、鼠李糖、果糖、岩藻糖、核糖、半乳糖醛酸、葡萄糖醛酸是组成枸杞多糖的主要成分。结论 微波辅助消解方法可以大大缩减枸杞多糖的消解时间,可用于快速检测枸杞多糖的含量。     

热带雨林博罗霍果多糖的单糖组成分析

研究了博罗霍果多糖的不同提取条件和对其含量及单糖的组成进行测定。方法1的提取条件为样品经乙醇溶液除去单糖和寡糖,脱脂、水提醇沉法提取多糖,用苯酚-硫酸法测定多糖含量,酸水解后用HPLC-ELSD法测定多糖组成。方法2的提取条件为样品经冷冻干燥,乙醇溶液除去单糖和寡糖后,用苯酚-硫酸法测定多糖含量,酸水解后用气相色谱衍生法测定多糖组成。方法1提取得多糖含量为6.2%,其单糖组成为半乳糖、阿拉伯糖、鼠李糖。方法2提取得多糖含量为11.2%,其单糖组成为半乳糖、阿拉伯糖、甘露糖和葡萄糖,糖醛酸含量为0.24%。博罗霍多糖是以中性糖为主且含少量糖醛酸的杂多糖。     

枸杞多糖结构及其单糖组分的分析研究

枸杞经乙醚脱脂和Sevag法脱蛋白后,用热水提取并用乙醇沉淀多糖,采用紫外光谱、红外光谱、气相色谱和FID检测器对枸杞多糖结构和功效成分单糖进行光谱分析和气相色谱分析。结果表明:枸杞多糖属于蛋白多糖,构杞多糖存在有官能团如—OH,C—O—C,C=O,-NH_2等,其糖苷键存在β-型糖苷键和α-构型的吡喃糖和呋喃糖。多糖为杂多糖,粗多糖得率为2.04%,采用DB-1701毛细管柱对乙酰化后的单糖能进行很好的色谱分离,其单糖组分至少含有8种以上的单糖:鼠李糖、岩藻糖、阿拉伯糖、木糖、甘露糖、半乳糖、葡萄糖等,其中含量较多的是阿拉伯糖、葡萄糖和半乳糖,它们的摩尔比1.956:0.835:0.629,其余的单糖含量比较低。     

亚麻籽胶化学组成和结构的研究

通过气相色谱测定表明,亚麻籽胶含有木糖、阿拉伯糖、半乳糖、葡萄糖、鼠李糖、岩藻糖六种单糖,其中木糖是亚麻籽胶的主要单糖组分,而岩藻糖是亚麻籽胶中含量最少的单糖组分。采用DEAE-SepharoseCL-6B柱层析将亚麻籽胶中多糖进行分离,研究结果表明,亚麻籽胶中多糖是由中性多糖和酸性多糖组成的,而且蛋白质是与酸性多糖结合在一起。Sepharose2B凝胶过滤色谱表明,亚麻籽胶的分子量较大,分布较均一。     

马齿苋多糖的超声提取及多糖中单糖组成分析

苯酚硫酸法测定多糖含量,用超声法提取马齿苋多糖,多糖的提取率可高达10.13%。对粗多糖用DEAE-纤维素柱分离,得到一种分子量为57kDa的均一性多糖,并进行理化性质测试。利用纸层析和气相色谱对马齿苋多糖中的单糖组成作了分析,此马齿苋多糖中的单糖组成有葡萄糖、半乳糖、甘露糖、果糖、木糖和阿拉伯糖。抗菌实验结果表明,马齿苋多糖对实验菌株有微弱的抑制和灭活作用。     

齿苋多糖的超声提取及多糖中单糖组成分析

苯酚硫酸法测定多糖含量,用超声法提取马齿苋多糖,多糖的提取率可高达10.13%.对粗多糖用DEAE-纤维素柱分离,得到一种分子量为57kDa的均一性多糖,并进行理化性质测试.利用纸层析和气相色谱对马齿苋多糖中的单糖组成作了分析,此马齿苋多糖中的单糖组成有葡萄糖、半乳糖、甘露糖、果糖、木糖和阿拉伯糖.抗菌实验结果表明,马齿苋多糖对实验菌株有微弱的抑制和灭活作用.     

高效毛细管电泳法测定黄泥螺黏液中活性多糖的单糖组成

目的:测定经提取纯化后黄泥螺黏液中3种活性多糖EBPA、EBPB1和EBPB2的单糖组成。方法:7种单糖标准品经α-萘胺衍生化以后,用不同浓度(55～85mmol/L)的硼砂作为电泳介质,探寻最佳电泳条件实现高效毛细管电泳分离,得到标准的a-萘胺衍生单糖的毛细管电泳区带电泳图谱。将提纯后的黄泥螺黏液中的3种活性多糖分别水解成单糖,用相同的方法在最佳电泳条件下经毛细管电泳分离,得到水解单糖的毛细管电泳图谱。结果:最佳工作条件:运行缓冲液为75mmol/L、pH10.4的硼砂水溶液,分离电压10kV,进样压力0.5Psi,进样时间10s,柱温25℃。通过与标准谱图对照分析,黄泥螺黏液中的活性多糖EBPA由鼠李糖、葡萄糖、甘露糖、阿拉伯糖和岩藻糖组成,EBPB1由鼠李糖、葡萄糖、甘露糖、阿拉伯糖、岩藻糖和半乳糖组成,EBPB2由葡萄糖、甘露糖、阿拉伯糖、岩藻糖和半乳糖组成。结论:高效毛细管电泳能有效分析多糖中单糖组分,灵敏度高,分离效果好。     

枸杞多糖的超滤分级及理化性质的研究

探究了超滤法分离对枸杞多糖理化性质的影响。采用截留分子量不同的超滤膜分离枸杞多糖,检测各个组分的分子量范围、多糖组成、多糖形貌和热力学性质,探究超滤分级对枸杞多糖理化性质的影响。超滤方法可以实现枸杞多糖的分级分离,得到分子量大小分别为2.03×106(LBP-8),3.62×106(LBP3-1),3.10×104(LBP1-4)的多糖组分,主要有岩藻糖、鼠李糖、阿拉伯糖、木糖、葡萄糖、甘露糖和半乳糖组成,都不含有核糖,LBP1-4不含有鼠李糖,LBP-8不含鼠李糖和葡萄糖。其总糖含量、半乳糖醛酸含量、中性糖含量、蛋白质含量,多糖形貌和热力学性质均显示差异性。     

阿里红中多糖的分离纯化及其组分分析

目的对阿里红中的多糖进行分离纯化,并对得到的两种多糖组分进行基础结构分析。方法阿里红经水提醇沉法除蛋白后,再经DEAE纤维素-52、Sepharose CL-6B和葡聚糖凝胶Sephadex G-100柱层析分离纯化得到两种多糖组分FOPS-a和FOPS-b。采用凝胶过滤法分析其纯度和相对分子量,经气相色谱法分析其单糖组成,并对多糖组分进行部分酸水解,高碘酸氧化和Smith降解分析。结果分离纯化得到的阿里红多糖组分FOPS-a、FOPS-b的相对分子质量为199 kDa和87 kDa。单糖组成均为甘露糖、阿拉伯糖、半乳糖。FOPS-a主链单糖残基为甘露糖,末端残基和分支单糖残基为阿拉伯糖、半乳糖、甘露糖和鼠李糖;FOPS-b主链单糖残基为甘露糖,末端残基和分支单糖残基为阿拉伯糖、半乳糖、甘露糖和葡萄糖。结论该研究可为阿里红多糖的开发与利用提供技术参考。     

糖枣多糖的单糖组成分析

研究糖枣多糖的单糖组成。以3 a生糖枣为试材,采用糖腈乙酸酯衍生化法,利用气相色谱仪对5个枣多糖组分进行单糖成分测定。结果表明,在糖枣多糖的单糖组成中,以木糖醇、葡萄糖、半乳糖所含比例较高,分别占单糖总含量的19.4%、18.5%、24.2%(组分DTC中葡萄糖比例高达36.4%);鼠李糖、核糖、阿拉伯糖和甘露糖,所占含量次之,分别为7.1%、6.5%、8.1%、7.9%;岩藻糖、木糖含量较低,分别只占总单糖质量的5.0%、3.4%(组分DTB1中岩藻糖只占0.80%,组分DTB2中木糖只占0.70%)。由此可知,糖枣多糖中单糖组成的差异性大。     

Arsenic content of some edible mushroom species

The arsenic contents of 162 fruit body samples of 37 common edible mushroom taxa were analyzed. The samples were gathered from different habitats of Hungary (mainly from mountains) between 1984 and 1999. The arsenic content of the samples was measured by the inductively coupled plasma spectrometry method. Very low [lower than 0.05 mg/kg dry matter (DM)] concentrations were found in the samples of 13 taxa, while higher (or very high) contents were quantified in other common taxa (the highest arsenic content was recorded in the fruit body of Laccaria amethysthea at 146.9 mg/kg DM). The species of eight genera (Agaricus, Calvatia, Collybia, Laccaria, Langermannia, Lepista, Lycoperdon, Macrolepiota) belong to the so-called accumulating taxa, and this tendency is evident on all habitats. This arsenic accumulation capability is found in two orders of Basidiomycetes (Agaricales and Gasteromycetales), which is to say this phenomenon occurs in the families Agaricaceae, Tricholomataceae and Gasteromycetaceae. The accumulating taxa found all have a saprotrophic type of nutrition; arsenic accumulation is not detectable in xilophagous or in mycorrhizal species. The consumption of the accumulating species found has only a low toxicological risk for three reasons: the consumed fresh fruit bodies contain about a tenfold lower arsenic level than the dried ones, the majority of arsenic occurs not in poisonous inorganic, but in less dangerous (or not poisonous) organic forms, and the frequency of consumption is low.     

Susceptibility of stored product insects to high concentrations of ozone at different exposure intervals

Ozone is a highly reactive gas with insecticidal activity. Past studies have indicated that ozone technology has potential as a management tool to control insect pests in bulk grain storage facilities. The objective of this study was to determine the efficacy of short periods of exposure to high ozone concentrations to kill all life stages of red flour beetle (Tribolium castaneum (Herbst)) (Coleoptera: Tenebrionidae), and Indianmeal moth (Plodia interpunctella (Hübner)) (Lepidoptera: Pyralidae), adult maize weevil (Sitophilus zeamais (Motsch.)) (Coleoptera: Curculionidae) and adult rice weevil (S. oryzae (L)) (Coleoptera: Curculionidae). Insects were treated with six ozone concentrations between 50 and 1800 ppm. The specific objective was to determine minimal time needed to attain 100% mortality. The most ozone-tolerant stages of T. castaneum were pupae and eggs, which required a treatment of 180 min at 1800 ppm ozone to reach 100% mortality. Eggs of P. interpunctella also required 180 min at 1800 ppm ozone to reach 100% mortality. Ozone treatments of 1800 ppm for 120 min and 1800 ppm for 60 min were required to kill all adult S. zeamais and adult S. oryzae, respectively. The results indicate that high ozone concentrations reduce the treatment times significantly over previously described results. Our results also provide new baseline information about insect tolerance to ozone treatment.     

Organization and localization of the dnaA and dnaK gene regions on the multichromosomal genome of Burkholderia multivorans ATCC 17616

The Burkholderia multivorans strain ATCC 17616 carries three circular chromosomes with sizes of 3.4, 2.5, and 0.9 Mb. To reveal the distribution and organization of the genes for fundamental cell functions on the genome of this bacterium, the dnaA and dnaK gene regions of ATCC 17616 were cloned and characterized. The gene organization of the dnaA region was rnpA-rmpH-dnaA-dnaN-gyrB with a single consensus DnaA-binding box (TTATCCACA) between the rmpH and dnaA genes. This intergenic region, however, did not work as an autonomously replicating sequence in ATCC 17616. On the other hand, the gene organization of the dnaK region was grpE-orf1 (gene for thioredoxin homologue)-dnaK-dnaJ-pabB (gene for p-aminobenzoate synthetase component homologue). A putative heat-shock promoter that showed good homology to the sigma32-dependent promoter consensus sequence in Escherichia coli was found upstream of the grpE gene, suggesting that these five genes constitute an operon. In M9 succinate minimal medium the dnaJ mutant grew more slowly than the wild-type strain, indicating that this operon is functional. Pulsed-field gel electrophoresis and Southern blot analyses indicated that both the dnaA and dnaK gene regions exist as single copies on the 3.4 Mb chromosome.     

Contamination with storage fungi of human food from Cameroon

In a mycological study, a total of 95 human food samples were investigated to evaluate the incidence of fungal contamination in Cameroon by conventional identification method and partly confirmed by DNA sequencing. The isolated fungal spp. were further studied to determine their toxigenic potentials. The investigation revealed the predominance of Aspergillus and Penicillium with 96% of samples contaminated with at least one species of these fungi, whereas the incidence of co-contamination of samples was 85%. Aspergillus flavus and Aspergillus parasiticus (Flavi section) were the most predominant species contaminating mainly maize and peanuts. In addition, P. crustosum and P. polonicum were the most common contaminants belonging to the genus Penicillium. On the other hand, A. ochraceus (Circumdati section) registered a low incidence rate of 5%, including other members of the Aspergillus group. Other members of the genera Rhizopus and Alternaria spp. were also registered in the study. A majority of fungal strains of A. ochraceus, A. parasiticus, P. crustosum and P. polonicum isolated were toxigenic, producing the mycotoxins tested for, while none was detected in cultures of A. fumigatus. The high incidence rate of fungi contamination coupled with their potentials in producing mycotoxins gives a strong indication that the samples tested may likely be contaminated with various mycotoxins. There is need for further study to assess the incidence of mycotoxins contamination in similar food samples.     

Assessment of the microbiological safety of salad vegetables and sauces from kebab take-away restaurants in the United Kingdom

The purpose of this study was to establish the microbiological safety of salad vegetables and sauces served in kebab take-away restaurants. Comparison with published microbiological guidelines revealed that 4.7% of 1213 salad vegetable samples were of unsatisfactory microbiological quality due to Escherichia coli and/or Staphylococcus aureus levels at ≥10² cfu g⁻¹. Another 0.3% of salad samples were of unacceptable quality due to S. aureus at ≥10⁴ cfu g⁻¹ (2 samples) or the presence of Salmonella Kentucky (1 sample). Cucumber was the most contaminated salad vegetable with regards to unsatisfactory levels of E. coli (6.0%) or S. aureus (4.5%). Five percent of 1208 sauce samples were of unsatisfactory microbiological quality due to E. coli, S. aureus at ≥10² cfu g⁻¹ and/or Bacillus cereus and other Bacillus spp. at ≥10⁴ cfu g⁻¹. A further 0.6% of sauce samples were of unacceptable quality due to Bacillus spp. (Bacillus subtilis, Bacillus pumilus, Bacillus licheniformis) at ≥10⁵ cfu g⁻¹ or the presence of Salmonella Agbeni (1 sample). More samples of chilli sauce (8.7%) were of unsatisfactory or unacceptable microbiological quality than any other sauce types. The results emphasize the need for good hygiene practices in kebab take-away restaurants handling these types of ready-to-eat products.     

Formation of cereulide and enterotoxins by Bacillus cereus in fermented African locust beans

Afitin, iru and sonru are three spontaneously fermented African locust bean Benin condiments. The fermentation processes are exothermic, with temperatures mostly being above 40 °C. A total of 19 predominant Bacillus cereus isolates from afitin, iru and sonru, were investigated. The enterotoxin genes nhe (A, B, C) were present in all 19 isolates, the hbl (A, C, D) in one (afitin), and the cytK gene in three isolates (afitin). Levels of cytotoxicity to Vero cells and NheA production in BHI-broth was within the range of known diarrheal outbreak strains. Autoclaved cooked African locust beans inoculated with emetic (cereulide producing) B. cereus Ba18H2/RIF supported growth at 25, 30 and 40 °C with highly different maximum cereulide productions of 6 ± 5, 97 ± 3 and 0.04 ± 0.02 μg/g beans, respectively (48 h). For non-autoclaved cooked beans inoculated with 2, 4 and 6 log₁₀B. cereus Ba18H2/RIF spores/g beans, cereulide production was 5 ± 4, 64 ± 8 and 69 ± 34 μg/g beans, respectively at 24 h, while it was 70 ± 43, 92 ± 53 and 99 ± 31 μg/g at 48 h of fermentation at 30 °C. Even though high toxin levels were observed, to date there are no known reports on diarrhea or vomiting due to the consumption or afitin, iru and sonru in Benin, which also according to the present study is likely to be expected from the low levels of cereulide produced at 40 °C.     

Comparison of the most odour-active volatiles in different hop varieties by application of a comparative aroma extract dilution analysis

Application of a comparative aroma extract dilution analysis on the volatiles isolated from five different hops (Hallertau Perle, Hallertau Hersbrucker Spät, Slowenian Golding, Hallertau Smaragd, US Cascade) revealed linalool and myrcene with the highest Flavour Dilution (FD)-factors in all varieties, followed by 2-isopropyl-3-methoxypyrazine, 3-methylbutanoic acid and geraniol. Some odourants, however, showed high FD-factors only in certain varieties, for example, (5Z)-octa-1,5-dien-3-one and germacrene B in Hersbrucker Spät, (3E,5Z)-undeca-1,3,5-triene in Hersbrucker Spät and Cascade and nonanal in Cascade. The overall odour profile of the Cascade sample clearly differed from the other varietes, and was dominated by a black currant like odour note. The identification experiments revealed 4-methyl-4-sulfanylpentan-2-one, so far unknown as hop constituent, as key contributor to this odour. In addition, an odour-active undecatetraene was present, in particular, in Perle and Cascade. Synthesis and structural assignment of the four stereoisomers of (3E)-undeca-1,3,5,9-tetraene allowed the identification of the fresh, pineapple-like smelling compound as (3E,5Z,9E)-undeca-1,3,5,9-tetraene. Among the four isomers synthesised, this compound showed by far the lowest odour threshold of 0.01 ng/L in air.     

Diversity of lactic acid bacteria in suan-tsai and fu-tsai, traditional fermented mustard products of Taiwan

Fu-tsai and suan-tsai are spontaneously fermented mustard products traditionally prepared by the Hakka tribe of Taiwan. We chose 5 different processing stages of these products for analysis of the microbial community of lactic acid bacteria (LAB) by 16S rRNA gene sequencing. From 500 LAB isolates we identified 119 representative strains belonging to 5 genera and 18 species, including Enterococcus (1 species), Lactobacillus (11 species), Leuconostoc (3 species), Pediococcus (1 species), and Weissella (2 species). The LAB composition of mustard fermented for 3 days, known as the Mu sample, was the most diverse, with 11 different LAB species being isolated. We used sequence analysis of the 16S rRNA gene to identify the LAB strains and analysis of the dnaA, pheS, and rpoA genes to identify 13 LAB strains for which identification by 16S rRNA gene sequences was not possible. These 13 strains were found to belong to 5 validated known species: Lactobacillus farciminis, Leuconostoc mesenteroides, Leuconostoc pseudomesenteroides, Weissella cibaria, and Weissella paramesenteroides, and 5 possibly novel Lactobacillus species. These results revealed that there is a high level of diversity in LAB at the different stages of fermentation in the production of suan-tsai and fu-tsai.     

Feeding deterrent activity of terpenoid lactones with a p-menthane system against stored-product pests

Feeding deterrent activity of eight enantiomeric pairs and one optically inactive terpenoid lactone with a p-menthane system against three storage pests was determined. The lactones were tested on adults of Sitophilus granarius, adults and larvae of Tribolium confusum and larvae of Trogoderma granarium. The isomeric starting natural compounds, (+) and (−) pulegones and (+) and (−) isopulegols, were also tested. The results showed that the introduction of the lactone moiety into the p-menthane system produced antifeedant activity in the lactones obtained. The lactones with a spiro arrangement of lactone and cyclohexane rings were more active than those with condensed rings. The configuration of chiral centres present in the molecule significantly influenced the activity of the compounds studied. In most cases, lactones obtained from R-(+)-pulegone were more active antifeedants than those obtained from S-(−)-pulegone.