A new dynamic method for the rapid determination of the biodegradable dissolved organic carbon in drinking water

A new method for the determination of biodegradable dissolved organic carbon (BDOC), which may be useful to the water industry, is proposed. It is a dynamic method that measures the BDOC of circulating water continuously pumped across a biofilm attached to a special support that fills a system of two glass columns. The BDOC value corresponds to the difference in DOC between inlet and outlet water samples. The sampling may be intermittent or continuous, but the process is continuous. The biofilms give good performances over periods of at least 1 year. The analytical results are not significantly different from those of other bioassays based on the use of indigenous bacteria and the total duration of analysis is between 2 and 3 h.     

A new dynamic method for the rapid determination of the biodegradable dissolved organic carbon in drinking water

F. RIBAS, J. FRIAS AND F. LUCENA. 1991. A new method for the determination of biodegradable dissolved organic carbon (BDOC), which may be useful to the water industry, is proposed. It is a dynamic method that measures the BDOC of circulating water continuously pumped across a biofilm attached to a special support that fills a system of two glass columns. The BDOC value corresponds to the difference in DOC between inlet and outlet water samples. The sampling may be intermittent or continuous, but the process is continuous. The biofilms give good performances over periods of at least 1 year. The analytical results are not significantly different from those of other bioassays based on the use of indigenous bacteria and the total duration of analysis is between 2 and 3 h.     

A resazurin-based biosensor for organic pollutants

A new rapid biosensor method employing the dye resazurin as an indicator of bacterial respiration has been developed to provide a rapid, facile and specific biosensor for environmental contaminants that does not rely on genetic modification techniques, is suitable for a high-throughput multiwell format, and is ideally suited to resource-constrained environmental monitoring situations. This whole-cell biosensor has been applied to the test analyte toluene using natural toluene-degrading bacteria as the biological component and is competitive with more complex recombinant approaches. The redox-driven biosensor is dependent on the catabolism of a specific compound, concomitantly reducing the redox indicator resazurin to provide the analytical signal in a whole-cell biosensor assay.     

基于相平衡分配法的水体沉积物中有机污染物质量基准的研究进展

沉积物质量基准是对水质基准的补充,对水质管理具有重要意义.我国对沉积物质量基准研究起步较晚,且多集中于重金属质量基准,对有机物质量基准的研究较少.国际上建立沉积物质量基准的方法很多,而相平衡分配法被认为是建立水体沉积物中有机污染物质量基准行之有效的方法.本文介绍了运用相平衡分配法建立水体沉积物中有机污染物质量基准的研究进展,阐述了不可逆吸附的影响以及对相平衡分配法的改进,指出了相平衡分配法存在的一些问题及研究展望.     

Interaction between phosphorus and biodegradable organic carbon on drinking water biofilm subject to chlorination

Aims: To examine whether phosphorus and biodegradable organic carbon interact to impact biofilm density and physiological function of biofilm‐forming bacteria under conditions relevant to chlorinated drinking water distribution systems. Materials and Results: The 2 × 2 factorial experiments with low and high levels of phosphorus and biodegradable organic carbon were performed on 4 ‐week‐old drinking water biofilms in four separate pipe systems in the presence of chlorine. Experimental results revealed that biofilm heterotrophic plate count levels increased with the increase in biodegradable organic carbon concentration, showed no response to increases in levels of phosphorus and was not affected by interaction between phosphorus and biodegradable organic carbon. However, a significant positive interaction between phosphorus and biodegradable organic carbon was found to exist on biofilm mass and physiological function and/or metabolic potentials of biofilm communities; the effects of biodegradable organic carbon on biofilm mass and physiological function of biofilm‐forming bacteria were accelerated in going from low to high level of phosphorus. Conclusions: Biodegradable organic carbon was found to be the primary nutrient in regulating biofilm formation in drinking water regardless of the presence of chlorine. It can be therefore concluded that the removal of an easily biodegradable organic carbon is necessary to minimize the biofilm growth potential induced by the intrusion of phosphorus. Significance and Impact of the Study: Phosphorus introduced to drinking water may interact with biodegradable organic carbon, thus leading to measurable impact on the biofilm formation.     

A system for the on-line determination of glucose concentration

An off-line glucose analyzer, Yellow Springs Instrument (YSI) model 27 was modified and coupled to various peripheral components to produce a fast, fully automated system for the online determination of glucose concentration. The amount of time required to accomplish each measurement was in the order of two minutes. To demonstrate the utility of this system, various tests were performed. First, a stream containing known amounts of glucose was monitored on-line and the system was calibrated. The calibration curve was shown to be described by Michaelis-Menten kinetics. Once the system was properly calibrated, it was used to monitor the glucose concentration in the effluent stream of two different enzyme reactor systems. The glucose concentrations were within experimental error of those obtained via standard off-line techniques.     

A new approach to the rapid determination of protein side chain conformations

Two efficient algorithms have been developed which allow amino acid side chain conformations to be optimized rapidly for a given peptide backbone conformation. Both these approaches are based on the assumption that each side chain can be represented by a small number of rotameric states. These states have been obtained by a dynamic cluster analysis of a large data base of known crystallographic structures. Successful applications of these algorithms to the prediction of known protein conformations are presented.     

A proteomic approach for exploring biofilm in Streptococcus mutans

Biofilm formation by Streptococcus mutans is considered as its principal virulence factor, causing dental caries. Mutants of S. mutans defective in biofilm formation were generated and analyzed to study the collective role of proteins in its formation. Mutants were characterized on the basis of adherence to saliva-coated surface, and biofilm formation. The confocal laser microscopy and scanning electron microscopy images showed that the control biofilms had cluster of cells covered by layer of exo-polysaccharide while the biofilms of mutants were thin and spaced. Two-dimensional protein electrophoresis data analysis identified 57 proteins that are either up (44 proteins) or down (13 proteins) regulated. These data points to the importance of up and down regulated proteins in the formation of biofilm in Streptococcus mutans.     

A new device for rapid evaluation of biofilm formation potential by bacteria

This work describes the implementation of a new assay named the BioFilm Ring Test to evaluate the ability of bacteria to form biofilms. This assay is based on the immobilisation (or not) of magnetic beads embedded by bacterial aggregates or mats (patented concept). It is realised on modified polystyrene 96-wells microtiter plates with individual 8-wells slides. The kinetic of biofilm formation of four bacterial species, Listeria monocytogenes, Escherichia coli, Staphylococcus carnosus and Staphylococcus xylosus was evaluated with this new device by comparison with the standard crystal violet staining method of sessile cells. In parallel, the biofilm growth was visualized by Scanning Electron Microscopy (SEM) observations. The BioFilm Ring Test gave similar but faster results than the crystal violet method. Moreover, the new assay was easier to implement, more reproducible and allowed high throughput screenings due to limited manipulations (no washing and staining steps) and rapid and accurate measurements of magnetic bead immobilisation by sessile bacterial cells.     

A rapid method for quantitative determination of L-tryptophan

Summary A modified colorimetric technique automatized by an Alpkem micro-continuous flow analyser was described for estimating the concentration of L-tryptophan in fermentation broth. This approach provided a convenient alternative to HPLC for L-tryptophan estimation and may help to avoid the time-consuming and laborious screening work encountered in the strain improvement programme.     

持久性有机污染物的植物修复

简要介绍了持久性有机污染物,重点分析了植物对去除环境中持久性有机污染物的修复机制,指出了植物修复技术存在的问题和今后的发展方向。     

A flexible approach for on-line computerised quantification of intra-uterine pressure data

Utilising simple mathematical techniques of differential calculus, a computer program has been developed for real time, on-line processing of uterine contractions with a small computer. The area under the intra-uterine pressure-time curve is calculated and two distinctive values of this area are printed on-line every 512 sec. The ‘active area’, which is the area above the resting tone, is calculated in addition to the ‘total area’—that is, the area above 0 mmHg. This allows an objective and efficient assessment of uterine activity which may be used as a basis of comparison between individual patients and groups of patients.     

A rapid colorimetric method for the determination of mimosine

A rapid colorimetric method has been described for the quantitative determination of mimosine by using activated carbon as a decolorizing agent and measuring the intensity of mimosine-ferric chloride color produced.     

A rapid method for determination of ribonucleotide reductase activity

Ribonucleoside diphosphate reductase activity is determined in centrifuged homogenates by following the conversion of cytosine ribonucleotide to cytosine deoxyribonucleotide. The enzymatic reaction is measured by monitoring the radioactivity of the reaction products separated by thin layer chromatography on PEI-cellulose plates. The method is rapid and permits the simultaneous processing of multiple samples.     

Estimation of melting points of large set of persistent organic pollutants utilizing QSPR approach

The presence of polyhalogenated persistent organic pollutants (POPs), such as Cl/Br-substituted benzenes, biphenyls, diphenyl ethers, and naphthalenes has been identified in all environmental compartments. The exposure to these compounds can pose potential risk not only for ecological systems, but also for human health. Therefore, efficient tools for comprehensive environmental risk assessment for POPs are required. Among the factors vital for environmental transport and fate processes is melting point of a compound. In this study, we estimated the melting points of a large group (1419 compounds) of chloro- and bromo- derivatives of dibenzo-p-dioxins, dibenzofurans, biphenyls, naphthalenes, diphenylethers, and benzenes by utilizing quantitative structure—property relationship (QSPR) techniques. The compounds were classified by applying structure-based clustering methods followed by GA-PLS modeling. In addition, random forest method has been applied to develop more general models. Factors responsible for melting point behavior and predictive ability of each method were discussed.