牛蒡提取液对副溶血性弧菌的抑制作用

研究了牛蒡提取物对副溶血性弧菌的抑制作用。采用80%乙醇分别浸提两个牛蒡品种柳川理想及黄肌牛蒡根的皮及去皮根,四种提取物分别命名为LP、LR、HP和HR。采用滤纸片扩散和最低抑菌浓度法筛选了四种提取物的抑菌效果,时变抑菌研究了常温(25℃)和低温(4℃)下牛蒡提取物在无菌蒸馏水(DW)以及脑心浸汤(BHI)中对副溶血性弧菌的抑制效果。结果显示,四种提取物中LP的抑菌活性最好;经1000μL/mL LP提取液7小时处理,在4℃和25℃DW环境均未有副溶血性弧菌检出;经各浓度提取液1天处理,在4℃和25℃BHI环境均未有副溶血性弧菌检出。LP对副溶血性弧菌弧菌具有良好的抑制作用。     

超临界CO_2萃取法提取棘托竹荪中的活性物质及其抑菌效果研究

本文研究了超临界CO2萃取法的不同提取条件对棘托竹荪中活性物质的抑菌效果影响。通过L16(43)正交实验,选取萃取压力、萃取温度与萃取时间为主要影响因素,采用超临界CO2萃取法,以活性物质对单增李斯特菌和副溶血性弧菌的最小抑菌浓度(MIC)与抑菌率作为提取效果指标,设计棘托竹荪抑菌活性物质的最佳提取条件。由不同提取条件对两种菌抑菌效果的影响程度与显著性分析得出:萃取时间萃取温度萃取压力。棘托竹荪活性物质提取的最佳条件为:萃取压力为20 MPa,萃取温度35℃,萃取时间120 min,所得活性物质对单增李斯特菌与副溶血性弧菌的MIC均为15.0 mg/m L。当抑菌活性物质浓度为MIC时,处理24 h后其对单增李斯特菌与副溶血性弧菌的最佳抑制率分别为85.7%与98.2%。     

环境压力条件与超高压对致病性副溶血性弧菌耐药性的影响（英文）

分析不同环境压力条件(温度、pH、渗透压和超高压)对12株致病性副溶血性弧菌耐药性的影响。利用微量肉汤稀释法测定菌株在不同温度(37℃和30℃)、渗透压(1%和6%NaCl)、pH(6.0和9.0)及超高压(180、250和300 MPa)条件影响下,其对所测抗生素的最小抑菌浓度(MIC)。结果表明,在1%和6%NaCl质量分数、pH 9.0条件下,副溶血性弧菌的耐药性增强,而在30℃、pH 6和超高压条件影响下,其耐药性减弱。此外,菌株在所测环境压力条件影响下,其对环丙沙星和头孢类抗生素的耐药性基本保持不变。环境压力条件的改变可能会增强致病性副溶血性弧菌的耐药性。     

副溶血性弧菌在动态体外人胃仿生原位消化系统中的存活情况研究

副溶血性弧菌(Vibrio parahaemolyticus)是一种经口摄入感染的食源性致病菌,广泛存在于水产品中,然而其进入人胃后的存活情况尚属研究空白。本研究将浓度为10~7 cfu/g的副溶血性弧菌接种于三文鱼和南美白对虾中,运用体外人胃仿生原位消化系统进行消化模拟,经过120 min后,测定食物排空率、胃部pH值变化及幽门排出食糜中副溶血性弧菌的存活情况。结果显示三文鱼的胃排空滞后时间为60 min,南美白对虾为90 min,模拟消化120 min时,两种食糜均未完全排空。胃部pH值为(1.6±0.1),在食物摄入10 min后大幅上升,随着胃酸的不断分泌及食物的消化分解,其pH值开始下降,并保持在5.41左右。在食品消化120 min进入肠道后,副溶血性弧菌并没有完全被胃酸杀灭,对虾中该菌的存活率为(0.119±0.025)%,而三文鱼中存活率为(0.007±0.005)%。综上所述,副溶血性弧菌可随食物基质的消化分解通过胃排空进入肠道,从而躲避胃酸的杀灭并导致人体患病。     

生食贝类水产品中副溶血性弧菌的半定量风险评估

为研究上海市生食贝类水产品的食用安全性,进行了半定量风险评估。牡蛎、醉泥螺、象拔蚌、北极贝为上海市主要的生食贝类水产品,调查显示贝类水产品中副溶血性弧菌平均检出率为43.7%,其中副溶血性弧菌致病性基因Tdh+/Trh+在贝类水产品中的平均检出率为3.75%。对上海地区对生食贝类的消费情况进行了膳食调查,并利用"Risk Ranger"软件对牡蛎、醉泥螺、象拔蚌、北极贝中副溶血性弧菌进行了半定量风险评估。上海市生食贝类消费人群比例为13.86%,生食贝类的食用频率平均2.4月/餐次,平均每餐消费生食贝类水产品为49.06 g/餐。风险评估结果显示:牡蛎/副溶血性弧菌(50)属于高度风险,醉泥螺/副溶血性弧菌(46)、象拔蚌/副溶血性弧菌(44)、北极贝/副溶血性弧菌(39)均属于中度风险,根据风险排序风险大小依次为牡蛎醉泥螺象拔蚌北极贝。     

不同温度条件下副溶血性弧菌tdh基因表达及其代谢组响应

【目的】采用RT-PCR的方法分析致病性副溶血性弧菌毒力基因表达,并应用代谢组学的方法研究毒力基因不同表达水平下致病性副溶血性弧菌代谢组的响应。【方法】本文以致病性副溶血性弧菌(Vibrio parahaemolyticus)ATCC33846为材料,分别提取不同温度(4、25和37℃)下菌体总RNA和代谢组。采用相对定量的方法检测副溶血性弧菌tdh基因在不同温度条件下的表达差异,同时应用超高压液相色谱-四级杆飞行时间质谱联用仪(UPLC/Q-TOF-MS)系统为工作平台检测其代谢组。采用主成分分析法(principal component analysis,PCA)比较副溶血性弧菌代谢组轮廓差异,并通过皮尔森和斯皮尔曼相关性分析法分析代谢组与tdh基因表达之间相关性。【结果】结果表明,不同温度条件下tdh基因表达强弱的排列顺序25℃4℃37℃;在tdh基因不同表达水平下发生显著性(P0.05)变化的主要代谢物是有机酸、氨基酸、醇、酮、酯;共得到11种代谢物与tdh基因表达高度相关(相关性系数︱r︱=1,P0.05),其中3种为负相关,8种为正相关,且醇类代谢物与tdh基因表达的正相关性最显著。【结论】本研究发现副溶血性弧菌代谢组与毒力基因表达存在一定的相关性,有望为副溶血性弧菌致病机理的深入探究提供一定的理论支持。     

四重PCR检测副溶血性弧菌及其毒力基因方法的建立

【目的】建立同时检测副溶血性弧菌tox R、tdh、trh、tlh基因的四重PCR快速检测方法。【方法】分别以副溶血性弧菌的tox R、tdh、trh、tlh 4个基因为靶基因,设计4对特异性引物,对4对引物浓度和退火温度进行优化,获得最佳引物比例和扩增条件,建立快速检测致病性副溶血性弧菌的四重PCR体系。通过特异性验证、灵敏度验证以及模拟样品检测进行方法确认。【结果】四重PCR体系扩增条带与预期相符,即115 bp(tox R)、244 bp(tdh)、418 bp(trh)、759 bp(tlh)4个目的条带;用74株副溶血性弧菌和37株非目标菌的测试结果表明,所建立的方法有良好的特异性。该方法对模板DNA的检测灵敏度为50μg/L,纯培养物的检测灵敏度为6.7×103 CFU/m L;副溶血性弧菌含量为1.36 CFU/g的人工模拟样品增菌6 h后,tox R、tlh、tdh、trh 4个基因可同时被检出。【结论】该方法可实现同时检测携带tox R、tdh、trh、tlh 4种基因的副溶血性弧菌,对开展致病性副溶血性弧菌的检测研究具有一定现实意义。     

不同酒精度、盐度及酸碱度条件下醉泥螺中副溶血性弧菌的一级生长预测模型

通过分别控制酒精度、盐度、酸碱度三种单一变量腌制醉泥螺,测定醉泥螺中副溶血性弧菌的生长曲线,并采用SGompertz模型进行拟合,建立不同条件下的一级生长预测模型。结果表明酒精可以抑制副溶血性弧菌生长,而pH7.5和盐度3.3%的条件相对适合其生长。本文建立的醉泥螺中副溶血性弧菌在不同条件下的预测模型,可为醉泥螺安全性的预测、副溶血性弧菌的控制、工艺条件的改善提供依据。     

野生蓝莓提取物对四种致病菌的抑制作用

本研究选用中国野生蓝莓,研究了其提取物对铜绿假单胞菌、单增李斯特菌、金黄色葡萄球菌与副溶血性弧菌等四种致病菌的抑制作用,分别采用试管二倍稀释法和平板涂布法测定了野生蓝莓提取物的最小抑菌浓度(MIC)和最小杀菌浓度(MBC)。结果表明,野生蓝莓提取物对四种致病菌均有一定的抑制作用,对铜绿假单胞菌、单增李斯特菌、金黄色葡萄球菌与副溶血性弧菌的MIC分别为62.5、250、500 mg/m L与31.25 mg/m L,MBC分别为250、250、500与125 mg/m L。本研究首次报道了中国野生蓝莓对这四种致病菌的抑制作用,为中国野生蓝莓的开发和利用提供了依据。     

Production of ethanol from guava pulp by yeast strains

Guava pulp used for ethanol production by three yeast strains contained 10% (w/v) total sugars and was pH 4.1. Ethanol production at the optimum sugar concentration of 10%, at pH 4.1 and 30°C was 1.5%, 3.6% and 3.9% (w/v) by Saccharomyces cerevisiae MTCC 1972, Isolate-1 and Isolate-2, respectively, at 60 h fermentation. Higher sugar concentrations at 15 and 20% were inhibitory for ethanol production by all test cultures. The maximum production of ethanol at optimum natural sugar concentration (10%) of guava pulp, was 5.8% (w/v) at pH 5.0 by Isolate-2 over 36 h fermentation, which was only slightly more than the quantity of ethanol produced by Saccharomyces cerevisiae (5.0%) and Isolate-1 (5.3%) over 36 and 60h fermentation, respectively.     

Performance of a newly developed integrant of Zymomonas mobilis for ethanol production on corn stover hydrolysate

Efficient conversion of lignocellulosic biomass requires biocatalysts able to tolerate inhibitors produced by many pretreatment processes. Recombinant Zymomonas mobilis 8b, a recently developed integrant of Zymomonas mobilis 31821(pZB5), tolerated acetic acid up to 16 g l(-1) and achieved 82%-87% (w/w) ethanol yields from pure glucose/xylose solutions at pH 6 and temperatures of 30 degrees C and 37 degrees C. An ethanol yield of 85% (w/w) was achieved on glucose/xylose from hydrolysate produced by dilute sulfuric acid pretreatment of corn stover after an overliming' process was used to improve hydrolysate fermentability.     

Effect of pH and lactic or acetic acid on ethanol productivity by Saccharomyces cerevisiae in corn mash

The effects of lactic and acetic acids on ethanol production by Saccharomyces cerevisiae in corn mash, as influenced by pH and dissolved solids concentration, were examined. The lactic and acetic acid concentrations utilized were 0, 0.5, 1.0, 2.0, 3.0 and 4.0% w/v, and 0, 0.1, 0.2, 0.4, 0.8 and 1.6% w/v, respectively. Corn mashes (20, 25 and 30% dry solids) were adjusted to the following pH levels after lactic or acetic acid addition: 4.0, 4.5, 5.0 or 5.5 prior to yeast inoculation. Lactic acid did not completely inhibit ethanol production by the yeast. However, lactic acid at 4% w/v decreased (P<0.05) final ethanol concentration in all mashes at all pH levels. In 30% solids mash set at pH ≤5, lactic acid at 3% w/v reduced (P<0.05) ethanol production. In contrast, inhibition by acetic acid increased as the concentration of solids in the mash increased and the pH of the medium declined. Ethanol production was completely inhibited in all mashes set at pH 4 in the presence of acetic acid at concentrations ≥0.8% w/v. In 30% solids mash set at pH 4, final ethanol levels decreased (P<0.01) with only 0.1% w/v acetic acid. These results suggest that the inhibitory effects of lactic acid and acetic acid on ethanol production in corn mash fermentation when set at a pH of 5.0–5.5 are not as great as that reported thus far using laboratory media.     

Single-cell protein of Rhodotorula sp. Y-38 from ethanol, acetic acid and acetaldehyde

Summary Continuous cultivation of Rhodotorula sp. Y-38 was carried out on ethanol, acetic acid or acetaldehyde. At a feed concentration of 1.0 % (w/v) ethanol, the cell yield of 64 g/100 g ethanol and crude protein of 52 g/100 g biomass were obtained at D=0.5 h^-1. The respective value of the content of amino acids and nucleic acids was 42.6 and 9.4 g/100 g biomass. At 2.0 % (w/v) acetic acid, cell yield was found to be 50 g/100 g acetic acid at D=0.4 h^-1. The optimum dilution rate ranged between 0.3 and 0.4 h^-1. At 0.05 % (w/v) acetaldehyde, the maximum cell yield was obtained at D=0.14 h^-1.     

Characterization of the psychrotolerant acetogen strain SyrA5 and the emended description of the species Acetobacterium carbinolicum

A psychrotolerant, obligate anaerobic, acetogenic bacterium designated strain SyrA5 was isolated from black anoxic sediment of a brackish fjord. Cells were Gram-positive, non-sporeforming rods. The isolate utilized H(2)/CO(2), CO, fructose, glucose, ethanol, ethylene glycol, glycerol, pyruvate, lactate, betaine and the methyl-groups of several methoxylated benzoic derivatives such as syringate, trimethoxybenzoate and vallinate. The optimum temperature for growth was 29 degrees C, whilst slow growth occurred at 2 degrees C. The strain grew optimally with NaCl concentrations below 2.7% (w/v), but growth occurred up to 4.3% (w/v) NaCl. Growth was observed in the range from pH 5.9 to 8.5, optimum at pH 8. The G+C content was 44.1 mol%. Based upon 16S rRNA gene sequence analysis and DNA-DNA reassociation studies, the organism was classified in the genus Acetobacterium. Strain SyrA5 shared a 16S rRNA sequence similarity with A. carbinolicum of 100%, a fthfs gene (which codes for the N5,N10 tetrahydrofolate synthetase) sequence identity of 98.5-98.7% (amino acid sequence similarities were 99.4-100%) and a RNA-DNA hybridization homology of 64-68%. Despite a number of phenotypic differences between strain SyrA5 and A. carbinolicum we propose including strain SyrA5 as a subspecies of A. carbinolicum for which we propose the name Acetobacterium carbinolicum subspecies kysingense. The type strain is SyrA5 (=DSM 16427(T), ATCC BAA-990).     

Aqueous two-phase assisted by ultrasound for the extraction of anthocyanins from Lycium ruthenicum Murr.

In this study, an efficient ultrasound-assisted aqueous two-phase extraction method was used for the extraction of anthocyanins from Lycium ruthenicum Murr. An ethanol/ammonium sulfate system was chosen for the aqueous two-phase system due to its fine partitioning and recycling behaviors. Single-factor experiments were conducted to determine the optimized composition of the system, and the response surface methodology was used for the further optimization of the ultrasound-assisted aqueous two-phase extraction. The optimal conditions were as follows: a salt concentration of 20%, an ethanol concentration of 25%, an extraction time of 33.7?min, an extraction temperature of 25°C, a liquid/solid ratio of 50:1 w/w, pH value of 3.98, and an ultrasound power of 600?W. Under the above conditions, the yields of anthocyanins reached 4.71?mg/g dry sample. For the further purification, D-101 resin was used, and the purity of anthocyanins reached 25.3%. In conclusion, ultrasound-assisted aqueous two-phase extraction was an efficient, ecofriendly, and economical method, and it may be a promising technique for extracting bioactive components from plants.     

Improved ethanol production from various carbohydrates through anaerobic thermophilic co-culture

Saccharification is one of the most critical steps in producing lignocellulose-based bio-ethanol through consolidated bioprocessing (CBP). However, extreme pH and ethanol concentration are commonly considered as potential inhibitors for the application of Clostridium sp. in CBP. The fermentations of several saccharides derived from lignocellulosics were investigated with a co-culture consisting of Clostridium themocellum and Clostridium thermolacticum. Alkali environments proved to be more favorable for ethanol production. Fermentation inhibition was observed at high ethanol concentrations and extreme pH. However, low levels of initial ethanol addition resulted in an unexpected stimulatory impact on the final ethanol productions for all cultures under selected conditions. The co-culture was able to actively ferment glucose, xylose, cellulose and micro-crystallized cellulose (MCC). The ethanol yield observed in the co-culture was higher (up to twofold) than in mono-cultures, especially in MCC fermentation. The highest ethanol yield (as a percentage of the theoretical maximum) observed was 75% (w/w) for MCC and 90% (w/w) for xylose.     

Recovery of the proteose peptone component 3 from cheese whey in Reppal PES 100/polyethylene glycol aqueous two-phase systems

Recovery of the proteose peptone component 3 from cheese whey was optimal using a 16% (w/w) Reppal PES 100 – 24% (w/w) PEG 600 aqueous two-phase system, at pH 7, giving a mass recovery yield of 99% and a purity of 83% for proteose peptone component 3 in the upper phase. Using the above system a partition coefficient of 30.7 and a purification factor of 6.9 were achieved.     

Ethanol production by immobilized Saccharomyces cerevisiae, Saccharomyces uvarum, and Zymomonas mobilis

Saccharomyces cerevisiae NRRL Y-2034, S, uvarum NRRL Y-1347, and Zymomonas mobilis NRRL B-806 each were separately immobilized in a Ca-alginate matrix and incubated in the presence of a free-flowing and continuous 1, 3, 5, 10, or 20% (w/w) glucose solution. In general, the yeast cells, converted 100percnt; of the 1, 3, and 5% glucose to alcohol within 48 h and maintained such a conversion rate for at least two weeks. The bacterium converted ca. 90% (w/w) of the 1, 3, and 5% glucose to alcohol continuously for one week. However, both the yeast and bacterium were inhibited in the highest glucose (20% w/w) solution. All of the immobilized cultures produced some alcohol for at least 14 days. Immobilized S. cerevisiae was the best alcohol producer of all of the glucose concentrations; the yeast yielded 4.7 g ethanol/100 g solution within 72 h in the 10% glucose solution. After 7-8 days in the 10% solution, S. cerevisiae produced ethanol at 100% of theoretical yield (5.0 g ethanol/100 g solution), with a gradual decrease in alcohol production by 14 days. Immobillized S. uvarum produced a maximum of 4.0 g ethanol/100 g solution within 2 days and then declined to ca. 1.0 g ethanol/100 g solution after 7 days continuous fermentation in the 10% glucose solution. Zymomonas mobilis reached its maximum ethanol production at 4 days (4.7 g/100 g solution), and then diminished similarly to S. uvarum. The development of a multiple disk shaft eliminated the problem both of uneven distribution of alginate-encapsulated cells and of glucose channeling within the continuous-flow fermentor column. This invention improved alcohol production about threefold for the yeast cells.     

Production of fuel ethanol at high temperature from sugar cane juice by a newly isolated Kluyveromyces marxianus

Kluyveromyces marxianus DMKU 3-1042, isolated by an enrichment technique in a sugar cane juice medium supplemented with 4% (w/v) ethanol at 35 degrees C, produced high concentrations of ethanol at both 40 and 45 degrees C. Ethanol production by this strain in shaking flask cultivation in sugar cane juice media at 37 degrees C was highest in a medium containing 22% total sugars, 0.05% (NH(4))(2)SO(4), 0.05% KH(2)PO(4), and 0.15% MgSO(4).7H(2)O and having a pH of 5.0; the ethanol concentration reached 8.7% (w/v), productivity 1.45 g/l/h and yield 77.5% of theoretical yield. At 40 degrees C, a maximal ethanol concentration of 6.78% (w/v), a productivity of 1.13 and a yield 60.4% of theoretical yield were obtained from the same medium, except that the pH was adjusted to 5.5. In a study on ethanol production in a 5l jar fermenter with an agitation speed of 300 rpm and an aeration rate of 0.2 vvm throughout the fermentation, K. marxianus DMKU 3-1042 yielded a final ethanol concentration of 6.43% (w/v), a productivity of 1.3g/l/h and a yield of 57.1% of theoretical yield.