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Merlin Raud Evelin Linde Elo Kibena Siiri Velling Toomas Tenno Ene Talpsep Timo Kikas 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2010,85(7):957-961
BACKGROUND: Semi‐specific microbial biochemical oxygen demand (BOD) biosensors were constructed using living cells of Escherichia coli R17.1.3 (E. coli) and Raoultella terrigena P74.3 (R. terrigena) immobilized in agarose gel matrix. The research involved comparison with the Pseudomonas fluorescens P75 (P. fluorescens) biosensor that had no specificity in decomposing lactose and milk derivates. The constructed BOD biosensors were calibrated with OECD synthetic wastewater and tested with different wastewater samples. RESULTS: The linear range of the calibration curve was 5–200 mg L?1 BOD7 for R. terrigena and P. fluorescens based biosensors and 150 mg L?1 BOD7 for the E. coli based biosensor. Service life was 60 days for E. coli and P. fluorescens based biosensors and 40 days for R. terrigena based biosensors. BOD values for dairy industry wastewater obtained with current semi‐specific biosensors considerably overestimate BOD7, while universal biosensors underestimate BOD7 obtained by the conventional 7‐day BOD test. CONCLUSION: In spite of extensive overestimation of BOD7 the semi‐specific biosensors enabled better estimation of BOD in dairy industry wastewater than a reference P. fluorescens biosensor. The best result, in terms of service life, stability, sensitivity and reproducibility was accomplished with semi‐specific E.coli biosensor. Copyright © 2010 Society of Chemical Industry 相似文献
23.
Frederico A. Lima Olga Silva Santos Alan William Vilela Pomella Eloízio J. Ribeiro Miriam Maria de Resende 《Journal of surfactants and detergents》2020,23(1):91-98
Total biosurfactant production by Bacillus amyloliquefaciens IT45 was evaluated with different substrates concentrations in a culture medium. A central composite design (CCD) was developed to evaluate the influence of variables, including glucose syrup, yeast extract, and calcium chloride, on surface tension (ST), total biosurfactant production, and residual sugar (RS). As a result, the best observed results for ST, RS, and total biosurfactant production were 30 mN m−1, 31%, and 5.5 g L−1, respectively, after 48 h of fermentations carried out in batch operation process. Characterization of the biosurfactant identified the presence of surfactin. To validate the CCD experiments, fermentations were conducted in a 40 L pilot bioreactor. For this fermentation, the cellular growth was 3.0 × 109 CFU mL−1, surfactin production was 0.55 g L−1, and RS was 28%. The results demonstrate that B. amyloliquefaciens IT45 has the potential to produce biosurfactants and does not require high concentrations of carbon and nitrogen sources for its development. 相似文献
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目前,市场上有许多可供选择的分析仪,有些具备非常特殊的专业用途,有些则提供了较多的通用射频测量能力;有些被称为频谱分析仪,有些则被称为信号分析仪.这些分析仪都是用来测量和显示信号频率与幅度之间的关系的.如何在众多型号的分析仪中选择合适的一款需要多方面的考虑,本文将为您解答在挑选市场上各种分析仪时所遇到的疑问,并帮助您做出正确的选购决定. 相似文献
25.
A new concept is presented for selective and sensitive determination of trace metals via electrothermal atomic absorption spectrometry based on the principle of bead injection (BI) with renewable reversed-phase surfaces in a sequential injection-lab-on-valve (SI-LOV) mode. The methodology involves the use of poly(styrene-divinylbenzene) beads containing pendant octadecyl moieties (C18-PS/DVB), which are preimpregnated with a selective organic metal chelating agent prior to the automatic manipulation of the beads in the microbore conduits of the LOV unit. By adapting this approach, the immobilization of the most suitable chelating agent can be effected irrespective of the kinetics involved, optimal reaction conditions can be used for implementing the chelating reaction of the target metal analyte with the immobilized re-agent, and an added degree of freedom is offered in selecting the most favorable elution mode in order to attain the highest sensitivity. The potential of the SI-BI-LOV scheme is demonstrated by taking Cr(VI) as a model analyte, using a 1,5-diphenylcarbazide (DPC)-loaded bead column as the active microzone. As this reaction requires the use of high acidity, it is also shown that the bead material exhibits excellent chemical stability at low pH values. On-line pH sample adjustment prevents alteration of the original distribution of chromium species while ensuring fast rates for the DPC-Cr(VI) reaction. The proposed procedure was successfully applied to the determination of trace levels of Cr(VI) in natural waters containing high levels of dissolved salts (such as seawater and hard tap water) without requiring any dilution step. Method validation was performed by determination of total chromium in an NIST standard reference material (NIST 1640, natural water) after Cr(III) oxidation, and the results were in good agreement with the certified value. 相似文献
26.
Aouani H Mahboub O Bonod N Devaux E Popov E Rigneault H Ebbesen TW Wenger J 《Nano letters》2011,11(2):637-644
Controlling the fluorescence emission from nanoscale quantum emitters is a key element for a wide range of applications, from efficient analytical sensing to quantum information processing. Enhancing the fluorescence intensity and narrowing the emission directivity are both essential features to achieve a full control of fluorescence, yet this is rarely obtained simultaneously with optical nanoantennas. Here we report that gold nanoapertures surrounded by periodic corrugations transform standard fluorescent molecules into bright unidirectional sources. We obtain enhancement factors of the fluorescence count rate per molecule up to 120 fold simultaneously with a directional emission of the fluorescence into a narrow angular cone in the direction normal to the sample plane. The bright emission and narrow directionality enable the detection of single molecules with a low numerical aperture objective, and improve the effectiveness of fluorescence-based applications. We thoroughly quantify the increased light-matter coupling as well as the radiation pattern intensity. These results are highly relevant for the development of single molecule sensing, single-photon sources, and light emitting devices. 相似文献
27.
Mingguang Chen Wangxiang Li Thaís Eloá da Silveira Venzel Guanghui Li Mikhail E. Itkis Robert C. Haddon Elena Bekyarova 《Materials Today》2018,21(9)
Alignment of densely packed single-walled carbon nanotubes (SWNTs) largely preserves the extraordinary electronic properties of individual SWNTs in the alignment direction, while in transverse direction the films are very resistive due to large energy barriers for tunneling between adjacent SWNTs. We demonstrate that chromium atoms inserted between the sidewalls of parallel SWNTs effectively coordinate to the benzene rings of the nanotubes via hexahapto bonds that preserve the nanotube-conjugated electronic structure and serve as a conduit for electron transfer. The atomically interconnected aligned SWNTs exhibit enhanced transverse conductivity, which increases by ~2100% as a result of the photoactivated organometallic functionalization with Cr. The hexahapto mode of bonding the graphitic surfaces of carbon nanotubes with transition metal atoms offers an attractive route to the reversible chemical engineering of the transport properties of aligned carbon nanotube thin films. We demonstrate that a device fabricated with aligned SWNTs can be reversibly switched between a state of high electrical conductivity (ON) by light and low electrical conductivity (OFF) by applied potential. This study provides a route to the design of novel nanomaterials for applications in electrical atomic switches, optoelectronic and spintronic devices. 相似文献
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N Reunanen J Westermarck L H?kkinen TH Holmstr?m I Elo JE Eriksson VM K?h?ri 《Canadian Metallurgical Quarterly》1998,273(9):5137-5145
Inflammatory cytokines tumor necrosis factor-alpha and interleukin-1 trigger the ceramide signaling pathway, initiated by neutral sphingomyelinase-elicited hydrolysis of cell membrane phospholipid sphingomyelin to ceramide, a new lipid second messenger. Here, we show that triggering the ceramide pathway by sphingomyelinase or C2- and C6-ceramide enhances collagenase-1 (matrix metalloproteinase-1; MMP-1) gene expression by fibroblasts. C2-ceramide activates three distinct mitogen-activated protein kinases (MAPKs) in dermal fibroblasts, i.e. extracellular signal-regulated kinase 1/2 (ERK1/2), stress-activated protein kinase/Jun N-terminal-kinase (SAPK/JNK), and p38. Stimulation of MMP-1 promoter activity by C2-ceramide is dependent on the presence of a functional AP-1 cis-element and is entirely inhibited by overexpression of MAPK inhibitor, dual specificity phosphatase CL100 (MAPK phosphatase-1). Activation of MMP-1 promoter by C2-ceramide is also effectively inhibited by kinase-deficient forms of ERK1/2 kinase (MEK1/2) activator Raf-1, ERK1 and ERK2, SAPK/JNK activator SEK1, or SAPKbeta. In addition, ceramide-dependent induction of MMP-1 expression is potently prevented by PD 98059, a selective inhibitor of MEK1 activation, and by specific p38 inhibitor SB 203580. These results show that triggering the ceramide signaling pathway activates MMP-1 gene expression via three distinct MAPK pathways, i.e. ERK1/2, SAPK/JNK, and p38, and suggest that targeted modulation of the ceramide signaling pathway may offer a novel therapeutic approach for inhibiting collagenolytic activity, e.g. in inflammatory disorders. 相似文献
30.
S. Salin A. Vanhatalo S. Jaakkola K. Elo J. Taponen R.C. Boston T. Kokkonen 《Journal of dairy science》2018,101(12):11364-11383
High energy intake in the dry period has reportedly had adverse effects on mobilization of body reserves, dry matter intake, and productivity of dairy cows. We investigated whether grass silage (GS) fed ad libitum (high energy intake, HEI; 141% of daily metabolizable energy requirements) in an 8-wk dry period affects metabolic adaptation—specifically, peripheral insulin resistance—compared with a total mixed ration consisting of GS, wheat straw, and rapeseed meal (55/40/5%; controlled energy intake, CEI; 108% of metabolizable energy/d) fed ad libitum. Multiparous Ayrshire dairy cows (n = 16) were used in a randomized complete block design until 8 wk after parturition. Commercial concentrates were fed 1 and 2 kg/d during the last 10 to 6 and 5 to 0 d before the expected calving date, respectively. Postpartum, a similar lactation diet with ad libitum access to GS and increasing concentrate allowance (maximum of 16 kg/d) was offered to all. The HEI group gained more body weight and had higher plasma insulin, glucose, and β-hydroxybutyrate concentrations than the CEI group prepartum. Postpartal plasma glucose tended to be higher and milk yield was greater from wk 5 onward for HEI compared with CEI cows. An intravenous glucose tolerance test (IVGTT) was performed at ?13 ± 5 d and 9 ± 1 d relative to calving. The HEI cows had greater insulin response to glucose load and smaller area under the response curve for glucose than CEI cows in prepartal IVGTT. Thus, compensatory insulin secretion adapted to changes in insulin sensitivity of the peripheral tissues, preserving glucose tolerance of HEI cows. Higher insulin levels were needed in HEI cows than in CEI cows to elicit a similar decrement of nonesterified fatty acid concentration in prepartal IVGTT, suggesting reduced inhibition of lipolysis by insulin in HEI cows before parturition. In conclusion, high energy intake of moderately digestible GS with low concentrate feeding in the close-up dry period did not have adverse effects on metabolic adaptation, insulin sensitivity, and body mobilization after parturition. Instead, this feeding regimen was more beneficial to early-lactation performance than GS-based total mixed ration diluted with wheat straw. 相似文献