Biomedical subjects

Olga C Nunes

Publications and source records attributed to Olga C Nunes.

10 recordsLinked to original sources

PubMed2006

The influence of activated carbon surface properties on the adsorption of the herbicide molinate and the bio-regeneration of the adsorbent.

In the present study, the effect of the textural and surface chemistry properties of the activated carbon were evaluated in a combined treatment system to remove the herbicide molinate from waters. The process consists of an initial adsorption step followed by the bio-regeneration of the activated carbon through the utilization of a defined bacterial mixed culture (DC), previously described as able to mineralize molinate. Molinate adsorption and partial bio-regeneration was favoured with activated carbons with larger pores, consisting mainly of meso and macropores. In order to study the effect of different surface chemical characteristics while maintaining the original textural properties, a commercial activated carbon was submitted to thermal and nitric acid treatments. The thermal treatment improved the molinate adsorption capacity of activated carbon. However, the bio-regeneration of the nitric acid oxidised activated carbon was slightly higher. With all the activated carbon materials used it was observed that the biological consumption of molinate present in the liquid phase displaced the equilibrium towards the activated carbon partial regeneration.

Adsorption↗

PubMed2006

Treatment of cork boiling wastewater using chemical oxidation and biodegradation.

Three cultures were enriched from cork boiling wastewater using tannic acid as the selective carbon substrate, at 25 degrees C and pH 7.2, 25 degrees C and pH 4.7 and 50 degrees C and pH 4.7. The enrichment culture obtained at neutral pH was composed of five culturable isolates, whereas from each acidic enrichment two bacterial strains were isolated. Mesophilic isolates were Gram negative bacteria belonging to the genera Klebsiella, Pseudomonas, Stenotrophomonas and Burkholderia. Thermophilic isolates were members of the genus Bacillus. Despite the capability of the enrichment cultures to use tannic acid as single carbon and energy source, those cultures were unable to reduce the total polyphenols or the total organic carbon content of cork boiling wastewater. In order to increase the bioavailability of the organic carbon in cork boiling wastewater, biodegradation was preceded by Fenton oxidation. It was demonstrated that the combined process, using small amounts of Fenton reagents and biodegradative inoculum added almost simultaneously to cork boiling wastewater, leads to TOC reductions of more than 90%.

Biodegradation, Environmental↗

PubMed2006

Antibiotic resistance of enterococci and related bacteria in an urban wastewater treatment plant.

The main objective of this work was to study the ecology of enterococci and related bacteria in raw and treated wastewater from a treatment plant receiving domestic and pretreated industrial effluents in order to assess the influence of treatment on the prevalence of antibiotic resistance phenotypes among this group of bacteria. The predominant species found in the raw wastewater were Entercoccus hirae, Entercoccus faecium and Entercoccus faecalis. Wastewater treatment led to a reduction in E. hirae (alpha<0.1) and an increase in E. faecium (alpha<0.1); the relative proportions of E. faecalis remained the same in the raw and in the treated wastewater. Among the isolates tested, no vancomycin resistance was observed among the enterococci. Entercoccus faecium and E. faecalis showed resistance prevalence values reaching 33%, 40% and 57% for the antibiotics ciprofloxacin, erythromycin and tetracycline, respectively. Antibiotic-resistant strains of enterococci were not eliminated by wastewater treatment. A positive selection of ciprofloxacin-resistant enterococci was indicated by a significant increase in resistance prevalence (alpha<0.02) in treated wastewater compared with the raw wastewater.

Anti-Bacterial Agents↗

PubMed2005

Effect of operating parameters on molinate biodegradation.

The effect of operating conditions during molinate degradation by the defined mixed bacterial culture DC, previously described as able to mineralize molinate, was evaluated in a batch reactor. Parameters such as the rate of molinate degradation, the dissolved organic carbon (DOC) consumption and the accumulation of molinate degradation products were monitored along the culture growth. The effect of conditions such as temperature, pH, aeration rate, salinity, and presence of additional carbon and/or nitrogen sources, was tested independently. Degradation of molinate in river water was also evaluated. Culture DC was able to grow and to mineralize molinate at all the conditions assayed. Temperature was the factor with the strongest influence on bacterial growth and molinate mineralization. The lowest and the highest rate values of growth (0.010 and 0.110 h(-1)) and of molinate degradation (0.027 and 0.180 g molinate g(-1)celldrywth(-1)) were obtained at 15 and 35 degrees C, respectively. In cultures with approximately 187 mgl(-1) of molinate, 2-oxo-molinate was the major molinate degradation product accumulated in the medium, in concentrations below 0.133 mgl(-1). Degradation of molinate was also evaluated in a continuous stirred tank reactor (CSTR). Operating the CSTR at a hydraulic retention time (HRT) of 83 h, fed with medium containing molinate concentrations ranging from 1 to 3mM, culture DC degraded the herbicide with specific degradation rates similar to those obtained in the batch systems.

Azepines↗

PubMed2005

A case study of molinate application in a Portuguese rice field: herbicide dissipation and proposal of a clean-up methodology.

This study was designed to monitor molinate losses in surface and underground waters during Ordram application in a rice field situated in central Portugal. Water samples were collected from different sites, before, during and about one month and a half after Ordram application. Molinate quantification was based on a solid-phase microextraction (SPME) method followed by gas chromatography with flame photometric detector (GC-FPD) analysis, and led to the conclusion that the herbicide was dissipated in the environment, reaching levels as high as 3.9 microgl(-1) in underground water and 15.8 microgl(-1) in the river receiving tail waters. The feasibility of the application of treatment methodologies based on adsorption or biodegradation as processes to remove molinate from real-world waters was assessed. These methods seem suitable to reduce molinate concentrations to values in the range of the legally recommended limits (<0.5 microgl(-1)).

Azepines↗

PubMed2004

Preliminary feasibility study for the use of an adsorption/bio-regeneration system for molinate removal from effluents.

This work studies the feasibility of the use of a combined physical-biological remediation procedure for treatment of effluents contaminated with molinate, where the herbicide is removed through adsorption and biodegraded in a subsequent stage, with the regeneration of the adsorbent. In order to select the most adequate absorbent for molinate, different materials were tested, namely pine bark, activated carbon and resin Amberlite XAD-4. Activated carbon and resin Amberlite XAD-4 were the most efficient on the removal of molinate from solutions, although the activated carbon used proved not to be bio-regenerable. It was also observed that factors such as temperature, pH, and conductivity did not affect significantly molinate adsorption onto resin Amberlite XAD-4. Resin Amberlite XAD-4 was successfully bio-regenerated, being observed that biodegradation was mainly dependent on spontaneous desorption of the molinate. After bio-regeneration, the resin could be re-utilised as adsorbent.

Adsorption↗

PubMed2004

Gulosibacter molinativorax gen. nov., sp. nov., a molinate-degrading bacterium, and classification of 'Brevibacterium helvolum' DSM 20419 as Pseudoclavibacter helvolus gen. nov., sp. nov.

A Gram-positive, molinate-degrading bacterium, strain ON4(T) (=DSM 13485(T)=LMG 21909(T)), was isolated from a mixed bacterial culture able to mineralize the herbicide molinate. The strain was strictly aerobic, oxidase- and catalase-positive and non-acid-fast, with a growth temperature of 10-41 degrees C. It contained the major menaquinone MK-9 and a cell-wall peptidoglycan based on D-ornithine. 16S rDNA sequence analysis revealed that the strain formed a distinct line of descent in the family Microbacteriaceae, showing the highest 16S rDNA similarity ( approximately 95 %) to members of the genus Curtobacterium and 'Brevibacterium helvolum' DSM 20419 (=ATCC 13715). The latter was reported to have the cell-wall peptidoglycan type B2gamma and the major menaquinone MK-9, which are typical of Clavibacter, but it is clearly separated from this genus at the phylogenetic level. Based on low values of 16S rDNA sequence similarity to previously described genera and their distinctive phenotypic characteristics, it is proposed that strains ON4(T) and 'B. helvolum' DSM 20419 be classified as two novel genera and species, with the respective names Gulosibacter molinativorax gen. nov., sp. nov. and Pseudoclavibater helvolus gen. nov., sp. nov.

Actinomycetales↗

PubMed2003

A novel pathway for mineralization of the thiocarbamate herbicide molinate by a defined bacterial mixed culture.

A bacterial mixed culture able to mineralize molinate was established, through enrichment, using mineral medium with molinate as the only carbon, nitrogen and energy source. The combination of five cultivable isolates, purified from the enrichment culture, permitted the reconstitution of a degrading consortium. Both enrichment and defined cultures were able to mineralize molinate without accumulation of degradation products by the end of the growth. Among the five isolates constituting the defined mixed culture, an actinomycete, strain ON4, was essential for biodegradation, being involved in the cleavage of the thioester bond of molinate, the initial step of the degradation pathway. Isolate ON4 was able to grow on molinate at concentrations below 2 mM, with the accumulation of ethanethiol and diethyl disulphide. These sulphur compounds were toxic to strain ON4 when accumulating at higher concentrations. However, this inhibitory effect was avoided by the presence of other members of the mixed culture, out of which isolates ON1 and ON2 were observed to consume ethanethiol and diethyl disulphide. In this way, interactions among defined mixed culture members involve metabolic and detoxifying association.

Azepines↗

PubMed2003

Tepidiphilus margaritifer gen. nov., sp. nov., isolated from a thermophilic aerobic digester.

A moderately thermophilic bacterium is described, strain N2-214(T), that was isolated from an enrichment culture, growing on caprolactone, obtained from a sample from a water-treatment sludge aerobic digester operating at temperatures around 60 degrees C. The organism was aerobic, Gram-negative, oxidase- and catalase-positive, with a polar flagellum, and capable of growth at temperatures as high as 61 degrees C. The major fatty acids of strain N2-214(T) were C(16 : 0), C(18 : 1) and cyclo-C(19 : 0). The phylogenetic relationships of the strain, derived from 16S rRNA gene sequence comparisons, demonstrated it to be a member of the beta-subclass of the PROTEOBACTERIA: The highest 16S rDNA sequence similarity of isolate N2-214(T) was to Azoarcus buckelii (91.9 %), Thauera aromatica (92 %) and Hydrogenophilus thermoluteolus (92.7 %). On the basis of phylogenetic analyses and physiological and chemotaxonomic characteristics, it is proposed that isolate N2-214(T) (=DSM 15129(T)=LMG 21637(T)) represents a new genus and species, Tepidiphilus margaritifer gen. nov., sp. nov.

Betaproteobacteria↗

PubMed2003

Caenibacterium thermophilum gen. nov., sp. nov., isolated from a thermophilic aerobic digester of municipal sludge.

A bacterial strain, N2-680(T) (=DSM 15264(T)=LMG 21760(T)), isolated from a thermophilic aerobic digester of municipal sludge, was characterized with respect to its morphology, physiology and taxonomy. Phenotypically, the isolate was a Gram-negative rod with a polar flagellum, catalase- and oxidase-positive, containing cytoplasmic inclusions of poly-beta-hydroxybutyrate and had an optimal growth temperature of about 47 degrees C. Strain N2-680(T) was unable to reduce nitrate and could use organic acids, amino acids and carbohydrates as single carbon sources. Chemotaxonomic analysis revealed that ubiquinone 8 was the major respiratory quinone of this organism and that phosphatidylethanolamine and phosphatidylglycerol were the major polar lipids. At 50 degrees C, the major components in fatty acid methyl ester analysis were C(16 : 0) and cyclo-C(17 : 0). The highest 16S rDNA sequence identity of isolate N2-680(T) was to Leptothrix mobilis and Ideonella dechloratans (95.7 %) and to Rubrivivax gelatinosus and Aquabacterium commune (95.6 %). 16S rDNA sequence similarities to species of two related thermophilic genera, Caldimonas manganoxidans and Tepidimonas ignava, were lower (93.6 and 94.7 %). On the basis of phylogenetic analyses and physiological and chemotaxonomic characteristics, it is proposed that isolate N2-680(T) represents a new genus and species, for which the name Caenibacterium thermophilum gen. nov., sp. nov. is proposed.

Comamonadaceae↗