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排序方式: 共有2119条查询结果,搜索用时 15 毫秒
1.
This study was undertaken to develop a modified atmosphere package to control microbial growth in ready‐to‐eat (RTE) products stored at ambient temperature. Ethanol and/or limonene associated with modified atmosphere (CO2 : O2 : N2 = 30% : 5% : 65%) was used to inhibit the growth of total air‐borne microorganisms and Escherichia coli in RTE products stored at 25°C. The results indicated that 0.05% ethanol vapour in the headspace was effective to inhibit the growth of air‐borne microorganisms and E. coli at 25°C for 72 h in a model study, and the effectiveness was related to ethanol content. Both 73 ppm limonene and 0.05% ethanol vapour enhanced the bacteriostatic effect of modified atmosphere in RTE sushi roll products, and no off‐flavour was detected using this formulated gas; however, no significant inhibitory effect was observed for RTE cold noodle products. This study concludes that combinations of carbon dioxide, ethanol or limonene vapours are effective to inhibit microbial growth in RTE food at ambient temperature, and the outcome may be due to the hurdle effect. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
2.
Tuan Vo-Dinh Guy Griffin David L. Stokes Alan Wintenberg 《Sensors and actuators. B, Chemical》2003,90(1-3):104-111
We describe a multi-functional biochip (MFB), which uses two different types of bioreceptors, including nucleic acid and antibody probes, on a single platform. The multi-functional capability of the MFB device for biomedical diagnostics is illustrated by measurements of DNA probes specific to gene fragments of Bacillus anthracis and antibody probes targeted to Escherichia coli. Calibration curves for monitoring pathogenic species using antibody probes against E. coli and DNA probes for B. anthracis illustrate the capability of the device for medical diagnostics and for quantitative detection of pathogenic agents. 相似文献
3.
《International Journal of Food Science & Technology》2003,38(3):297-304
Summary The heat resistance of a four‐strain mixture of Escherichia coli O157:H7 was tested. The temperature range was 55–62.5 °C and the substrate was beef at pH 4.5 or 5.5, adjusted with either acetic or lactic acid. Inoculated meat, packaged in bags, was completely immersed in a circulating water bath and cooked to an internal temperature of 55, 58, 60, or 62.5 °C in 1 h, and then held for pre‐determined lengths of time. The surviving cell population was enumerated by spiral plating meat samples on tryptic soy agar overlaid with Sorbitol MacConkey agar. Regardless of the acidulant used to modify the pH, the D ‐values at all temperatures were significantly lower (P < 0.05) in ground beef at pH 4.5 as compared with the beef at pH 5.5. At the same pH levels, acetic acid rendered E. coli O157:H7 more sensitive to the lethal effect of heat. The analysis of covariance showed evidence of a significant acidulant and pH interaction on the slopes of the survivor curves at 55 °C. Based on the thermal‐death–time values, contaminated ground beef (pH 5.5/lactic acid) should be heated to an internal temperature of 55 °C for at least 116.3 min and beef (pH 4.5/acetic acid) for 64.8 min to achieve a 4‐log reduction of the pathogen. The heating time at 62.5 °C, to achieve the same level of reduction, was 4.4 and 2.6 min, respectively. Thermal‐death–time values from this study will assist the retail food processors in designing acceptance limits on critical control points that ensure safety of beef originally contaminated with E. coli O157:H7. 相似文献
4.
Cell suspensions of Escherichia coli as a model for bacterial populations in wastewaters were treated with ozone as a disinfectant in a continuously operated pilot plant with a plug flow reactor. Suspensions with an initial number of CFU (colony forming units) of 108 mL?1 were ozonized with ozone concentrations up to 12 mg/L. Metabolic activities and membrane functions break down with increasing ozone concentrations. The fluorochromization using 3′,6′-diacetylfluorescein (FDA) proved to be a suitable method for the detection of an alteration in permeability of the cell membranes and an inactivation of metabolic activity. By fluorescence microscopic and photometric investigations it could be clearly demonstrated that, in the case of disinfection with ozone, inactivation of the cells includes first of all a damage of the cell membranes. In contrast to the determination of the number of CFU, fluorochromization allows the detection of alteration in metabolic activities. 相似文献
5.
Post-harvest loss of resources to microbial competitors affects a number of species of animals, and many of them have evolved behaviors that reduce the likelihood of such loss. We previously described the inhibition ofBacillus psychrophilus by dogwood fruits (Cornus drummondii), which can comprise a significant portion of the winter food cache of the eastern woodrat (Neotoma floridana). The present study is a further investigation of the ability of dogwood fruits to inhibit growth ofB. psychrophilus. Additionally, we tested the antimicrobial activity of dogwood fruits onEscherichia coli andStaphlococcus aureus. Results of our study indicate that fresh fruits inhibit the growth ofB. psychrophilus andS. aureus but notE. coli. However, fruits taken from woodrat dens after four and six months storage inhibited growth of all three species of bacteria. Further, the strength of inhibition increased over the test period. We suggest the presence of an inhibitor allows woodrats to compete effectively for a valuable and limited food resource. 相似文献
6.
密码子优化的牛精蛋白基因在大肠杆菌中的表达 总被引:8,自引:0,他引:8
以PCR的方法得到牛精蛋白基因的基因,去其内含子,得到牛精蛋白cDNA,克隆入原核表达载体pGEX-2T中,组装成表达载体pGEX-2T-PE,利用大肠杆菌偏好的编码精氨酸的密码子CGT将野生型牛精蛋白基因中编码精氨酸的稀有密码子(AGA或AGG)替换掉,通过基因合成得到密码子优化的牛精蛋白的基因,将其克隆入原核表达载体pGEX-2T中,组装成表达载体pGEX-2T-PS。将这两个表达载体分别转化入大肠杆菌表达菌株BL21中,经IPTG诱导,同样条件下,野生型牛精蛋白基因无法得到表达,密码子优化的牛精蛋白基因能够得到良好的表达,表达产物约占细菌总蛋白的18%,将表达蛋白纯化,进行DNA-蛋白结合实验,发现其能与DNA发生非特异性的结合。 相似文献
7.
Hong Jin Mohammad S. Uddin Yu L. Huang Wah K. Teo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,59(1):67-72
High level expression of recombinant human tumour necrosis factor β (rh TNF-β) in Escherichia coli results in the formation of two portions of protein, namely soluble active protein and insoluble protein which is inactive and aggregates in the form of inclusion bodies (IBs). In this study, a procedure for purification and renaturation of rh TNF-β from inclusion bodies has been designed and verified experimentally with a product purity of more than 90% and a recovery of about 30%. The procedure includes washing of IBs with specific wash buffer (Triton X-100/EDTA/lysozyme/PMSF), their solubilization with 8 mol dm?3 alkaline urea, purification with ion-exchange columns, refolding with renaturation buffer and finally concentration and desalination with an ultrafiltration membrane. The characteristics of the renatured protein were identical with those of purified protein from the soluble fraction as demonstrated by (1) SDS-PAGE, (2) cytotoxic activity on mouse L929 cells, (3) N-terminal amino acid sequence, and (4) gel filtration chromatography. 相似文献
8.
L
P Fonseca J
M
S Cabral 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2002,77(10):1176-1185
An integrated process strategy for the recovery of penicillin acylase was developed, based on precipitation of non‐enzymatic proteins directly from Escherichia coli homogenates or crude extracts using Rolquat (quaternary ammonium salt) and adsorption of the enzyme on Amp‐Seph (3.8 µmole ampicillin cm?3) under pseudo‐affinity conditions. The effect of pH, concentrations of ammonium sulfate and Rolquat, and also concentrations of protein and cell debris on the precipitation of non‐enzymatic proteins from homogenates and crude extracts of penicillin acylase were analysed. The method of addition of Rolquat to homogenates and crude extracts significantly influenced the size of the precipitated particles. Improved results on the specific activity of penicillin acylase were obtained for 22% and 1% (w/v) of ammonium sulfate and Rolquat, respectively, added sequentially to enzyme solutions and at room temperature. Under these experimental conditions, the specific activity of penicillin acylase in homogenates and crude extracts was enhanced 2.5–3.0‐fold. Finally, the integrated process strategy was implemented first by precipitation of non‐enzymatic proteins and recovery of penicillin acylase directly from the enzyme solution treated with Rolquat using an adsorption/filtration system with an overall yield of 86%. This system allows simultaneously the filtration of cell debris and fine precipitated particles, in situ recovery of penicillin acylase by its adsorption on Amp‐Seph, and selective desorption of the enzyme with a specific activity of 11 IU (mg prot)?1 and a desorption yield of 95%. © 2002 Society of Chemical Industry 相似文献
9.
Kum‐Il Lee Yong‐Sik Yim Sang‐Wook Chung Jiaqiu Wei Jong Il Rhee 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(9):1036-1045
A two‐dimensional (2D) spectrofluorometer was used to monitor various fermentation processes with recombinant E coli for the production of 5‐aminolevulinic acid (ALA). The whole fluorescence spectral data obtained during a process were analyzed using artificial neural networks, ie self‐organizing map (SOM) and feedforward backpropagation neural network (BPNN). The SOM‐based classification of the whole spectral data has made it possible to qualitatively associate some process parameters with the normalized weights and variances, and to select some useful combinations of excitation and emission wavelengths. Based on the classified fluorescence spectra a supervised BPNN algorithm was used to predict some of the process parameters. It was also shown that the BPNN models could elucidate some sections of the process's performance, eg forecasting the process's performance. Copyright © 2005 Society of Chemical Industry 相似文献
10.
我们用扫描电镜观察肠道杆菌种(Enterobacteriaceae)中的四种细菌,大肠埃希氏杆菌(Escherichiacoli),普通变形杆菌(Proteus vulgaris),伤寒沙门氏菌(Salmonella typhi)和福氏志贺氏菌(Shigella Flexneri)。未处理的菌落标本,菌落表面都可形成一层厚薄不同的表膜(Surface film)。四种细菌菌落的表膜,形状不一,千姿百态。适当处理后的菌落标本,则可显示菌体的本来面目。四种细菌菌体在菌落表面的分布和排列,也是各不相同,千差万别。本文根据扫描电镜的观察,对四种不同菌落进行了讨论。 相似文献