微波辅助双水相提取百合多糖的工艺优化及其结构表征

为高效获取百合多糖和表征多糖结构，本文采用微波辅助双水相提取百合多糖，通过单因素实验和正交试验确定最佳的提取工艺；依次通过DEAE-52和Sephadex G-100柱色谱法纯化百合多糖粗提物，获得单一多糖馏分（LP2-SG），同时利用高效凝胶渗透色谱和气相色谱法分别测定LP2-SG的分子量和单糖组成，并对其结构进行初步表征。结果表明微波辅助双水相提取百合多糖的最优工艺为：微波功率400 W、硫酸铵质量分数20%和乙醇体积分数50%和料液比1:30 g/mL，百合多糖得率为10.15%±0.11%。纯化后的多糖馏分（LP2-SG）分子量为530.51 kDa，单糖组成为甘露糖、葡萄糖和半乳糖组成，其摩尔比为11.63:29.85:8.46。LP2-SG在260 nm和280 nm处无特征吸收，并具有典型的多糖红外光谱吸收特性。本研究结果为百合多糖的高效提取和深度开发提供重要参考。     

微波辅助提取山茱萸多糖工艺优化

利用微波辅助技术提取山茱萸多糖。在单因素试验的基础上以乙醇浓度、液料比和微波功率为试验因素,以多糖提取率为响应值,采用3因素3水平的响应面分析法进行试验。结果表明,山茱萸多糖提取的最佳工艺条件:浸泡时间120min,微波功率456W,料液比1∶33(m∶V),微波处理时间3.2min,实际测得多糖提取率为11.12%,与模型预测值基本相符。     

近江牡蛎多糖的结构鉴定及免疫调节能力分析

采用分级膜分离、DEAE-52阴离子交换层析法从近江牡蛎(Crassostrea rivularis)中分离纯化得到多糖CRP-1、CRP-2、CRP-3。采用高效凝胶渗透色谱法结合葡聚糖凝胶Sephadex G-100分离多糖,测定其分子质量及纯度;利用糖基基团测定、傅里叶变换红外光谱、高效液相色谱等方法对其结构进行解析。结果显示:CRP-1的总糖质量分数为(32.40±0.89)%,分子质量为124.5 kDa,是组分均一的多糖,由甘露糖、核糖、氨基葡萄糖、葡萄糖醛酸、半乳糖醛酸、葡萄糖、氨基半乳糖、半乳糖、阿拉伯糖组成,9种单糖的物质的量比为5.55∶0.32∶9.08∶0.47∶0.66∶48.13∶3.57∶8.53∶0.30;CRP-2的总糖质量分数为(78.50±1.90)%,分子质量为67.0 kDa,是由甘露糖、核糖、氨基葡萄糖、葡萄糖、氨基半乳糖、半乳糖组成,6种单糖的物质的量比为7.79∶0.41∶12.69∶32.08∶4.98∶15.92。CRP-3的总糖质量分数为(73.46±2.19)%,分子质量为8.3 kDa,是由氨基葡萄糖、半乳糖醛酸、葡萄糖组成,3种单糖的物质的量比为8.91∶5.71∶10.15。傅里叶变换红外光谱分析结果显示:CRP-1为多醛基吡喃环糖苷的多糖化合物;CRP-2为多酮基不饱和多糖化合物;CRP-3为多酮基含羧基多不饱和多糖化合物。以小鼠巨噬细胞系RAW264.7为模型,证明近江牡蛎多糖CRP-1、CRP-2、CRP-3具有免疫调节活性。     

石花菜多糖的分离纯化及单糖组成分析

以石花菜为原料,对石花菜多糖进行分离纯化,并对纯化后多糖组分的理化性质及单糖组成进行分析。利用复合酶法提取石花菜多糖并采用Sevage法脱蛋白,通过DEAE-52离子交换柱层析及Sephadex G-200凝胶柱层析对粗多糖进行分离纯化,按峰收集主要的多糖组分GAP1,对其总糖、蛋白质、糖醛酸及硫酸基质量分数进行测定,并采用1-苯基-3-甲基-5-吡唑啉酮(1-phenyl-3-methyl-5-pyrazolone,PMP)对多糖进行衍生化,通过高效液相色谱法测定其单糖组成。结果表明:石花菜粗多糖经柱层析后收集得到主要多糖组分GAP1,其总糖质量分数为92. 56%,糖醛酸质量分数为44. 53%,硫酸基质量分数为6. 92%,不含蛋白质; PMP柱前衍生高效液相色谱法测得GAP1主要由鼠李糖、葡萄糖醛酸、葡萄糖、半乳糖、木糖和L-岩藻糖6种单糖按照不同比例缩合而成,各单糖物质的量比为1. 00∶1. 00∶4. 45∶27. 31∶2. 27∶1. 88。     

超声-微波协同提取大豆种皮多糖性质及微观结构

本实验通过对大豆种皮多糖的总糖和蛋白质量分数、分子质量、单糖组成、傅里叶变换红外光谱进行测定,对扫描电子显微镜、原子力显微镜结果进行观察,深入分析超声-微波协同提取大豆种皮多糖性质及结构。结果表明,采用超声-微波协同提取的大豆种皮多糖中总糖质量分数可达(50.67±3.36)%,显著高于超声或微波提取的总糖质量分数;超声、微波及超声-微波协同提取的大豆种皮多糖均主要由半乳糖、甘露糖、半乳糖醛酸和鼠李糖组成,说明超声-微波协同技术未改变大豆种皮多糖的单糖种类,但对不同单糖所占比例有明显影响;超声-微波协同处理降低了多糖的多分散性,使多糖的不饱和度降低且支链的位置及数量发生变化,但未改变糖环类型。此外,超声-微波协同提取的大豆种皮多糖由直径较大的球形颗粒及疏松的网状结构组成,说明超声-微波可促进大豆种皮多糖分子聚集。通过探究超声-微波协同提取大豆种皮多糖的性质和微观结构,将为多糖结构解析提供一定的理论支持。     

超声-微波协同提取柚子皮多糖工艺优化及单糖组成、结构和抗氧化活性分析

以柚子皮为原料,采用超声-微波协同提取技术提取柚子皮多糖,优化最佳提取工艺,对其进行脱色、脱蛋白处理,对其单糖组成、结构和抗氧化活性进行分析。结果表明,超声-微波协同提取柚子皮多糖最佳工艺为:微波功率400 W,提取时间34 min,液料比39∶1(mL∶g),提取液pH 9.0,多糖得率为10.41%。紫外光谱分析表明无蛋白质及核酸残留,凝胶渗透色谱法测定柚子皮多糖平均分子质量为2.4×10^4 Da。液相色谱-质谱联用仪测定结果表明,柚子皮多糖是一种酸性杂多糖,由甘露糖、鼠李糖、葡萄糖醛酸、半乳糖醛酸、葡萄糖、半乳糖、阿拉伯糖组成,摩尔比为0.502∶0.960∶0.295∶6.331∶40.673∶10.732∶7.923。扫描电镜和红外光谱分析表明,柚子皮多糖主要为不规则碎片结构,伴有小的不规则颗粒,碎片表面粗糙,所得多糖呈不规则形状,表明柚子皮多糖具有非晶态结构,为吡喃型糖苷环骨架。抗氧化活性结果表明,柚子皮多糖具有较好的自由基清除效果,在质量浓度为1.0 mg/mL时,对1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基、羟自由基和2,2′-联氮-双-3-乙基苯并噻唑啉-6-磺酸[2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid),ABTS]自由基清除率分别为55.58%、46.32%、40.25%。该实验结果为柚子皮多糖的进一步分离纯化、结构解析、生物活性研究及开发具有潜力的功能性食品提供依据。     

山茱萸籽总黄酮的响应曲面法优化微波辅助提取工艺的研究

目的:利用微波辅助提取技术对山茱萸籽总黄酮的提取工艺进行研究。方法:以芦丁为对照品,采用紫外-分光光度法测定山茱萸籽中总黄酮的含量,以总黄酮含量为考察指标,采用响应曲面优化法(RSM)优化山茱萸籽总黄酮的提取工艺。结果:优化的山茱萸籽总黄酮微波辅助提取工艺参数为:微波功率350W,乙醇体积分数50%,液料比20mL/g,提取时间13min。在此最佳条件下,山茱萸籽总黄酮的一次提取率为6.68%。结论:山茱萸籽含有较高的总黄酮含量,所确定的提取工艺提取率高、速度快、操作简便。     

生姜皮多糖的分离纯化及其结构组成分析

以生姜皮为原料,经热水浸提法,乙醇醇沉得到生姜皮粗多糖。再经DEAE-纤维素-52阴离子交换柱和Sephadex?G-100凝胶柱对所得粗多糖进行层析纯化,得到3种水溶性生姜皮多糖(GE-1、GE-2、GE-3)。利用高效液相色谱与蒸发光散射检测器联用测定各多糖组分的分子质量,利用柱前衍生高效液相色谱法分析各多糖组分的单糖组成,通过紫外光谱扫描、红外光谱扫描进一步分析各组分多糖结构。结果表明3种纯化多糖组分总糖含量分别为(98.06±0.15)%、(97.41±0.42)%、(97.89±0.22)%,分子质量分别为462、194 k D和376 k D。GE-1的单糖组成主要为甘露糖、葡萄糖、木糖,含有微量的半乳糖,其物质的量比为1.25∶6∶1;GE-2的单糖组成主要为甘露糖、葡萄糖和岩藻糖,其物质的量比为2.51∶9.25∶1;GE-3的单糖组成主要为甘露糖、核糖、半乳糖、阿拉伯糖,其物质的量比为17.39∶1∶1.89∶1.23。紫外光谱扫描结果显示3种多糖组分无明显的核酸和蛋白质吸收峰,红外光谱结果分析得出GE-1、GE-2和GE-3含有多糖类物质的特征吸收峰。     

微波预处理-超声波提取山茱萸多糖及稳定性研究

以汉中山茱萸为原料,通过单因素及正交试验确定微波预处理-超声波提取山茱萸多糖的最佳工艺为:提取时间80 min,提取温度60℃,料液比1∶14(g/mL),醇沉浓度65%,多糖提取率达到16.83%。多糖提取物的稳定性实验结果表明,山茱萸中多糖在K+、Ca2+、Na+、Fe3+、Cu2+、柠檬酸钠、VC及氧化还原剂中稳定性较差,在Al3+、苯甲酸钠、酸性溶液中稳定性较好。     

万寿菊多糖的纯化、组成分析及其体外抗氧化和抗肿瘤活性研究

对万寿菊多糖(Tagetes erecta L.polysaccharides,TEPs)提取工艺进行优化并对粗多糖进行分离纯化,对得到的多糖组分进行单糖组成及体外抗氧化和抗肿瘤活性分析。响应面法优化万寿菊多糖最佳提取工艺为:提取温度80℃、提取时间2 h、料液比1∶21(g∶mL),此条件下提取率为3.7%。利用DEAE-52纤维素和Sephadex G-150柱层析分离纯化TEPs得2种均一多糖(TEPs-1和TEPs-2);利用高效体积排阻色谱法测定2种均一多糖重均分子量分别为4.69和5.73 k Da;利用1-苯基-3-甲基-5-吡唑啉酮(1-phenyl-3-methyl-5-pyrazolone,PMP)-柱前衍生HPLC法测定其单糖组成,TEPs两种组分均由7种单糖组成,其中甘露糖、半乳糖、葡萄糖和阿拉伯糖4种单糖含量较高。1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基、羟基自由基、超氧阴离子、2,2’-联氮-双-3-乙基苯并噻唑啉-6-磺酸(2,2’-azino-bis 3-ethylbenzthiazol...     

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.     

鸡源大肠埃希氏菌mcr-1基因携带及分析

目的 了解在农业农村部禁止使用多黏菌素作为动物促生长使用后四川部分地区鸡源大肠埃希氏菌（E.coli）mcr-1基因的携带情况,为制定进一步防控措施提供依据。方法 采集四川部分地区市场售卖点肉鸡直肠拭子,用含有多黏菌素（终浓度4 μg/mL）的EC肉汤增菌接种含多黏菌素（终浓度4 μg/mL）的麦康凯平板,挑取可疑菌落,采用PCR方法鉴定菌株并检测mcr-1基因;微量肉汤稀释法测定mcr-1基因阳性菌株对临床常见抗菌药物耐药情况。脉冲场凝胶电泳（PFGE）对mcr-1基因阳性菌株进行同源分析。耐药基因质粒结合实验验证mcr-1基因传播途径。结果 从70份肉鸡样本中的13份检出mcr-1基因阳性大肠埃希氏菌,检出率18.57%（13/70）,对实验的13种抗生素,除13株mcr-1阳性菌株对头孢西丁有12株敏感以外,对其他抗生素都表现出不同程度的耐药,其中四环素和甲氧苄啶/磺胺甲恶唑耐药率最高,达到了100%（13/13）;其次是氨苄西林和氯霉素,耐药率为84.62%（11/13）。PFGE显示13株mcr-1阳性大肠埃希氏菌分属13个不同的型别;质粒结合实验显示mcr-1基因能够通过质粒传播。结论 mcr-1基因在鸡大肠内大肠杆菌中检测率比较高,且鸡大肠中mcr-1阳性大肠埃希氏菌的耐药情况比较严重。     

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.     

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.     

Microbial profiles of frozen trimmings and silver sides prepared at Indian buffalo meat packing plants

To assess microbiological quality of buffalo meat trimmings (TT = 114) and silver sides (SS = 41), samples were collected from four different Indian meat packing plants. The aim of this study was: (i) to evaluate standard plate count (SPC), psychrotrophic count (PTC), Enterococcus feacalis count (EFC), Staphylococcus aureus count (SAC) and Escherichia coli count (ECC) and the presence of Salmonella spp. and Listeria monocytogenes; and (ii) also to determine vero toxic E. coli (VTEC) by polymerase chain reaction (PCR). TT samples had significantly higher (P < 0.001) SPC, PTC, EFC, and SAC than SS, while across the meat types there was no difference (P > 0.05) in ECC. E. coli was recovered from 32.4% TT and 19.5% SS samples. The prevalence rate of Salmonella spp. and L. monocytogenes in TT was 1.75% and 0.87%, respectively. But no SS sample was found to be positive for any of these two pathogens. VTEC was found in 2.58% of all the tested samples. This finding suggests that TT contain higher microbes but only small numbers of pathogens of latent zoonotic importance. The present study confirmed the importance of maintaining good process hygiene at meat plants for microbiological status of buffalo meat.     

Developmental and population growth rates of phosphine-resistant and -susceptible populations of stored-product insect pests

Phosphine resistance positively contributes towards an individual's fitness under phosphine fumigation. However, phosphine resistance may place resistant individuals at a fitness disadvantage in the absence of this fumigant, which can be exploited to halt or slow down the spread of resistance. This study aimed to determine if there is a fitness cost associated with phosphine resistance in populations of the red flour beetle (Tribolium castaneum (Herbst)), the lesser grain borer (Rhyzopertha dominica (F.)) and the sawtoothed grain beetle (Oryzaephilus surinamensis (L.)). The developmental rate and population growth of phosphine-resistant and -susceptible populations of these three species of stored-product insects were therefore determined under phosphine-free environment. The majority of the phosphine-resistant populations exhibited lower developmental and population growth rates than the susceptible populations indicating that phosphine resistance is associated with fitness cost in all three species, which can potentially compromise the fixation and dispersal of the resistant genotypes. Nonetheless, some phosphine-resistant populations did not show a fitness cost. Therefore, resistance management strategies based on suppression of phosphine use aiming at eventual reestablishment of phosphine susceptibility and subsequent reintroduction of this fumigant will be useful only for insect populations exhibiting a fitness cost associated with phosphine resistance. Therefore recognition of the prevailing phosphine-resistant genotypes in a region is important to direct the management tactics to be adopted.