Conventional Purification Process Research Articles

Simple two-step procedure for purification of cloned small sialidase from unclarified E. coli feedstocks

An efficient process for the purification of cloned small sialidase (pCPN-1, small nanH cloned from Clostridium perfringens) from unclarified E. coli feedstocks has been developed. In contrast to conventional purification processes, expanded bed adsorption (EBA) technique allows clarification, product recovery, and concentration to be combined into a single step operation. The cloned NanH was collected from both intra- and extracellular fractions, and purified by expanded bed ion-exchange chromatography followed by affinity chromatography. The EBA technique using STREAMLINE DEAE was shown to be successful in purifying NanH with a purification factor of 12 and yield of 93%. Successive purification of the concentrated NanH purified by an EBA column was achieved by affinity chromatography. The elution of adsorbed NanH was performed with 0.1 m NaHCO 3 buffer pH 9.0 and the pH of the eluted NanH was adjusted to 7.0. An overall yield of 88% was obtained after the affinity chromatographic step. The enzyme appeared to be homogeneous by polyacrylamide gel electrophoresis analysis. The molecular weight was measured as 43 KDa for cloned NanH. The procedure described is suitable for large-scale purification of cloned small NanH from unclarified E. coli feedstocks.

細胞毒性試験による有害化学物質汚染の評価

In environmental water has been reported the occurrence of thousands of chemicals, in which there are many toxic substances including carcinogens. These hazardous micropollutants may be not completely removed by conventional water purification process. To secure the safety of drinking water, it is highly necessary to monitor these toxic substances. For this purpose, simple bio-assay systems such as Ames test have been widely developed to monitor mutagenic micropollutants in water. In the present paper, the principle and limitation of bio-assay system were discussed. Based on the discussion, we examined whether cytotoxicity test is available as bioassay of water micropollutants. Cytotoxicity test using cultured HL-60 cells, liposomal damage test, and Ames mutagenicity test were applied to the substances recovered from tap and raw waters. No correlation was observed between the results of mutagenicity and cytotoxicity, while the results of cytotoxicity related to those of liposomal membrane damage. These results indicate that cytotoxicity tests will be effective to estimate the safety of drinking water and that a concept of cytotoxicity matrix may be available for identification of toxic micropollutants.

Membrane separations in ethanol recovery: an analysis of two applications of hyperfiltration

With further development, membrane separations have the potential to contribute to process improvements, especially for energy conservation, in ethanol fuel production. Two applications of hyperfiltration (reverse osmosis) in the recovery and purification of ethanol from fermentation beer are defined and analyzed for energy requirements and economics. These analyses are performed for a complete plant, including a recovery subprocess with and without the use of hyperfiltration. The hyperfiltration processes are designed using existing data for available membranes and hypothetical data for advanced membranes. The overall purpose of these analyses is to identify process modifications and membrane-related research that can contribute to decreasing the energy requirements of ethanol fuel production. In one application, hyperfiltration is used in a lignocellulose-to-ethanol plant to preconcentrate low-proof (2 wt% beer prior to further purification by fractional and azeotropic distillation. This application requires ethanol-rejecting membranes, which are developed. When lignocellulose is used as a feedstock for ethanol production, a low-proof beer is usually produced. The energy requirements of ethanol recovery from low-proof beer by conventional distillation exceed the energy content of ethanol and frequently preclude the feasibility of producing ethanol from lignocellulose. The use of hyperfiltration to preconcentrate ethanol can significantly reduce the energy requirements of ethanol recovery from low-proof beer. The analyses are based upon process designs using existing and hypothetical membranes. This application is found to conserve 19 to 20 GJ/m 3 (67,000 to 72,000 Btu/gal) of anhydrous ethanol as compared to only fractional and azeotropic distillation and to be economically competitive (with a 2 to 4% lower price). The analysis indicates that this application of hyperfiltration is promising and that future research should be devoted to increasing flux (while maintaining or improving ethanol rejection) and to assessing and improving membrane life. In the other application, hyperfiltration is used to dehydrate high-proof (93 to 95 wt%) ethanol in a corn-to-ethanol plant. Ethanol dehydration is an energy-intensive separation, generally requiring 2.0 to 2.8 GJ/m 3 (7,000 to 10,000 Btu/gal) of anhydrous ethanol. This application was designed based upon hypothetical, water-rejecting hyperfiltration membranes, which are not pres ently developed. Although the hyperfiltration process is found to conserve 0.8 GJ/m 3 (2,900 Btu/gal) of anhydrous ethanol, it is not found to have an economic advantage over a conventional ethanol purification process. Therefore, this application is not found to be promising and little incentive exists for performing research aimed at development of a water-rejecting membrane for the dehydration of ethanol by hyperfiltration. Finally, thoughts regarding the use of membrane separations in the chemical/fuel industry are presented.

Comparison of m-Endo LES, MacConkey, and Teepol media for membrane filtration counting of total coliform bacteria in water

Total coliform counts obtained by means of standard membrane filtration techniques, using MacConkey agar, m-Endo LES agar, Teepol agar, and pads saturated with Teepol broth as growth media, were compared. Various combinations of these media were used in tests on 490 samples of river water and city wastewater after different stages of conventional purification and reclamation processes including lime treatment, and filtration, active carbon treatment, ozonation, and chlorination. Endo agar yielded the highest average counts for all these samples. Teepol agar generally had higher counts then Teepol broth, whereas MacConkey agar had the lowest average counts. Identification of 871 positive isolates showed that Aeromonas hydrophila was the species most commonly detected. Species of Escherichia, Citrobacter, Klebsiella, and Enterobacter represented 55% of isolates which conformed to the definition of total coliforms on Endo agar, 54% on Teepol agar, and 45% on MacConkey agar. Selection for species on the media differed considerably. Evaluation of these data and literature on alternative tests, including most probable number methods, indicated that the technique of choice for routine analysis of total coliform bacteria in drinking water is membrane filtration using m-Endo LES agar as growth medium without enrichment procedures or a cytochrome oxidase restriction.

Behaviour in conventional sewage purification processes of coliform bacteria with transferable or non-transferable drug-resistance

Transferable ( R +) and non-transferable ( R −) resistance of coliform bacteria in settled sewage and after biofiltration, secondary sedimentation, chlorination and sand filtration was investigated. The percentage of R − coliforms resistant to ampicillin (A), chloramphenicol (C) or streptomycin (S), but not kanamycin (K) or tetracycline (T), was slightly reduced through the purification system. On the average the percentage of R + coliforms resistant to one or more of the same drugs was reduced by about 50%. This reduction was mainly accomplished by biofiltration and sand filtration. The ratio of transferable to non-transferable resistance for A, C, K or T increased during secondary sedimentation and chlorination. R factor transfer in water may explain these findings. Rapid passage over stony surfaces in biological and sand filters is unfavourable for conjugation and may damage sex pilli while R factor transfer can be expected under the relatively stagnant conditions in sedimentation and chlorination tanks. The incidence of R factors conferring resistance to all five drugs simultaneously increased through the purification system. These R factors are probably large and may carry markers which determine resistance to sewage purification processes. Between 30 and 40% of all R factors mediated resistance to at least four of the five drugs studied. The incidence of Escherichia coli I among R + coliforms varied but did not exceed 50%. The finding that conventional sewage purification has a limited effect on the incidence of drug resistance in bacteria supports the view that sewage should be treated by more advanced methods prior to discharge into the environment.