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At least 127 records · Page 7Linked to original sources

PubMed2005

Sorption of Cr(VI) from dilute solutions and wastewater by live and pretreated biomass of Aspergillus flavus.

Sorption of Cr(VI) was carried out from dilute solutions using live and pretreated biomass in a batch mode. Effects of agitation time, adsorbent dosage and pH were examined. The autoclaved biomass that showed maximum adsorption capacity (Q(0)=0.335 mg g(-1)) was used as an adsorbent in column studies. The optimized flow rate of 2.5 ml min(-1) and bed height 10 cm were used to determine the effect of metal ion concentration on removal of Cr(VI). Applying the BDST model to calculate the adsorption capacity (N(0)) of column, which showed 4.56 x 10(-5), 7.28 x 10(-5), 6.89 x 10(-5), 3.07 x 10(-5), 2.80 x 10(-5)mg g(-1) for 4, 8, 12, 16 and 20 mg dm(-3) of Cr(VI), respectively. Batch sorption proved to be more efficient than the column sorption and hence batch sorption was used to remove Cr(VI) from a textile dyeing industry wastewater. The phytotoxic effect of treated and untreated wastewater was studied against Zea mays. Toxicity was reduced by 50% in the treated effluent.

Adsorption↗

PubMed2004

Zeta potential as a measure of polyelectrolyte flocculation and the effect of polymer dosing conditions on cell removal from fermentation broth.

Characterization of flocculation for cell removal from fermentation broth via polyelectrolyte addition is commonly based on qualitative methods such as physical appearance of the floc. The use of zeta potential as a quantitative measure of floc character was evaluated as an indicator of optimal polymer addition. Zeta potential was found to increase with increasing cationic polyelectrolyte dosage, but never reached zero regardless of the total amount of polymer added, indicating flocculation occurs at least partially through a bridging type mechanism. Experiments were conducted using various polymer concentrations (25-75 g/L) and dosing methods (batch, incremental and continuous addition) that resulted in variable overall polymer requirements to achieve optimum flocculation. Zeta potential was found to be constant at optimal floc character regardless of the total amount of polymer added, polymer concentration, or method of polymer addition. Experiments with two additional types of fermentation broth also showed characteristic zeta potentials at optimal flocculation. Polymer requirements to achieve a particular floc character can vary greatly, depending on polymer dosing conditions and fermentation batch. The effect of polymer dosing conditions on the polymer requirement to obtain optimal floc character was evaluated. Polymer dosing method and calcium concentration were both found to have a significant effect (P < 0.0001) with continuous polymer addition and high calcium concentration requiring less polymer than did batch polymer addition and low calcium concentration, respectively. Polymer dosing concentration did not significantly affect polymer requirement for optimal flocculation.

Bacillus↗

PubMed2002

Hydraulic selection pressure-induced nitrifying granulation in sequencing batch reactors.

The effect of hydraulic selection pressure on the development of nitrifying granules was investigated in four column-type sequencing batch reactors (SBR). The nature of SBR is cycle operation, thus SBR cycle time can serve as a main hydraulic selection pressure imposed on the microbial community in the system. No nitrifying granulation was observed in the SBR operated at the longest cycle time of 24 h, due to a very weak hydraulic selection pressure, while the washout of nitrifying sludge was found in the SBR run at the shortest cycle time of 3 h, and led to a failure of nitrifying granulation. Excellent nitrifying granules with a mean diameter of 0.25 mm and specific gravity of 1.014 were developed in a SBR operated at cycle times of 6 h and 12 h, respectively. The results further showed that a short cycle time would stimulate microbial activity, production of cell polysaccharides and also improve the cell hydrophobicity. These hydraulic selection pressure-induced microbial changes favour the formation of nitrifying granules. This work, probably for the first time, shows that nitrifying granules can be developed at a proper hydraulic selection pressure in terms of SBR cycle time. Nitrifying granulation is a novel biotechnology which has a great potential for wastewater nitrification.

Bacteria↗

PubMedDate not supplied

Benzene transformation in nitrifying batch cultures.

The effect of benzene on the nitrifying activity of a sludge produced in steady-state nitrification was evaluated in batch cultures. Benzene at 10 mg/L inhibited nitrate formation by 53%, whereas at 5 mg/L there was no inhibition. For initial benzene concentrations of 0, 7, and 10 mg/L, the specific rates of NO(3)(-)-N production were 0.545 +/- 0.101, 0.306 +/- 0.024, and 0.141 +/- 0.010 g NO(3)(-)-N/g microbial protein-N.h, respectively. The specific rates of benzene consumption at 7, 12, and 20 mg/L were 0.034 +/- 0.003, 0.050 +/- 0.006, and 0.027 +/- 0.002 g/g microbial protein-N.h, respectively. Up to a concentration of 10 mg/L, benzene was first oxidized to phenol, which was later totally oxidized to acetate. Benzene at higher concentrations (20 and 30 mg/L) was converted to intermediates other than acetate, phenol, or catechol. These results suggest that this type of nitrifying consortium coupled with a denitrification system may have promising applications for complete removal of nitrogen and benzene from wastewaters.

Bacteria↗

PubMed2003

Lipase-catalysed transesterification of soya bean oil for biodiesel production during continuous batch operation.

The effects of temperature, oil/alcohol molar ratio and by-product glycerol were studied during Lipozyme TL IM-catalysed continuous batch operation when short-chain alcohols were used as the acyl acceptor. In non-continuous batch operation, the optimal oil/alcohol ratio and temperature were 1:4 and 40-50 degrees C; however, during the continuous batch operation, the optimal oil/alcohol ratio and temperature were 1:1 and 30 degrees C; 95% of enzymic activity remained after 10 batches when isopropanol was adopted to remove by-product glycerol during repeated use of the lipase.

2-Propanol↗

PubMed2004

Metabolic selectivity and growth of Clostridium thermocellum in continuous culture under elevated hydrostatic pressure.

The continuous culture of Clostridium thermocellum, a thermophilic bacterium capable of producing ethanol from cellulosic material, is demonstrated at elevated hydrostatic pressure (7.0 MPa, 17.3 MPa) and compared with cultures at atmospheric pressure. A commercial limitation of ethanol production by C. thermocellum is low ethanol yield due to the formation of organic acids (acetate, lactate). At elevated hydrostatic pressure, ethanol:acetate (E/A) ratios increased >10(2) relative to atmospheric pressure. Cell growth was inhibited by approximately 40% and 60% for incubations at 7.0 MPa and 17.3 MPa, respectively, relative to continuous culture at atmospheric pressure. A decrease in the theoretical maximum growth yield and an increase in the maintenance coefficient indicated that more cellobiose and ATP are channeled towards maintaining cellular function in pressurized cultures. Shifts in product selectivity toward ethanol are consistent with previous observations of hydrostatic pressure effects in batch cultures. The results are partially attributed to the increasing concentration of dissolved product gases (H2, CO2) with increasing pressure; and they highlight the utility of continuous culture experiments for the quantification of the complex role of dissolved gas and pressure effects on metabolic activity.

Acetic Acid↗

PubMed2004

Correspondence between community structure and function during succession in phenol- and phenol-plus-trichloroethene-fed sequencing batch reactors.

The effects of more than 2 years of trichloroethene (TCE) application on community succession and function were studied in two aerobic sequencing batch reactors. One reactor was fed phenol, and the second reactor was fed both phenol and TCE in sequence twice per day. After initiation of TCE loading in the second reactor, the TCE transformation rates initially decreased, but they stabilized with an average second-order rate coefficient of 0.044 liter mg(-1) day(-1) for 2 years. In contrast, the phenol-fed reactor showed higher and unstable TCE transformation rates, with an average rate coefficient of 0.093 liter mg(-1) day(-1). Community analysis by terminal restriction fragment length polymorphism (T-RFLP) analysis of the 16S rRNA genes showed that the phenol-plus-TCE-fed reactor had marked changes in community structure during the first 100 days and remained relatively stable afterwards, corresponding to the period of stable function. In contrast, the community structure of the phenol-fed reactor changed periodically, and the changes coincided with the periodicity observed in the TCE transformation rates. Correspondence analysis of each reactor community showed that different community structures corresponded with function (TCE degradation rate). Furthermore, the phenol hydroxylase genotypes, as determined by restriction fragment length polymorphism analysis, corresponded to community structure patterns identified by T-RFLP analysis and to periods when the TCE transformation rates were high. Long-term TCE stress appeared to select for a different and stable community structure, with lower but stable TCE degradation rates. In contrast, the community under no stress exhibited a dynamic structure and dynamic function.

Bacteria↗

PubMed2006

Kinetic and metabolic study of benzene, toluene and m-xylene in nitrifying batch cultures.

The effect of benzene, toluene, and m-xylene (BTX) compounds on the nitrifying activity of a sludge produced in steady-state nitrification was evaluated in batch cultures. Benzene and m-xylene at 10 mg C/L decreased ammonium consumption efficiency by 57% and 26%, respectively, whereas toluene did not affect the ammonium oxidation process. The consumed NH4+-N was totally oxidized to NO3- -N. There was no significant effect at 5 mg C/L of each aromatic compound. BTX (5-20mg C/L) induced a significant decrease in the values for specific rates of NH4+ -N consumption (76-99%) and NO3- -N production (45-98%). At 10 mg C/L of BTX compounds, the inhibition order on nitrate production was: benzene > m-xylene > toluene while at 20 mg C/L, the sequence changed to m-xylene > toluene > benzene for both nitrification inhibition and BTX compounds persistence. At 5 mg C/L of BTX compounds, there was no toxic effect on the sludge whereas from 10 to 50 mgC/L, bacteria did not totally recover their nitrifying activity. At a concentration of 5 mg C/L, toluene was first oxidized to benzyl alcohol, which was later oxidized to butyrate while m-xylene was oxidized to acetate and butyrate.

Benzene↗

PubMed2000

Reduced Growth Yield of Activated Sludge in Organic Protonophore-Containing Batch Culture.

The effects of organic protonophores 2,4-dinitrophenol (dNP) and para-nitrophenol (pNP) on the observed growth yield (Y(obs)) was studied using batch cultures of activated sludge microorganisms. A growth yield model was proposed in relation to the ratio of initial protonophore concentration (C(u)) to initial biomass concentration (X(0)) and was verified with experimental data. It was found that Y(obs) decreased with the increase of the C(u)/X(0) ratio, while the specific rate of glucose consumption was increased. Results showed that the C(u)/X(0) ratio could more reasonably reflect the real strength of organic protonophore exerted to activated sludge than using C(u) only. Based on the concept of growth yield, a model describing the uncoupling degree between energy generated via electron transport system and energy used for growth was further developed for protonophore-containing batch culture. It was shown that more than 60% of glucose was consumed through a futile cycle of energy rather than for growth at higher C(u)/X(0) ratios. This research usefully shows that the dissipation of energy via uncoupling biochemical processes can reduce excessive production of activated sludge markedly.

Journal Article↗

PubMed2006

Process development for the removal and recovery of hazardous dye erythrosine from wastewater by waste materials-Bottom Ash and De-Oiled Soya as adsorbents.

Erythrosine is a water-soluble xanthene class of dye. It is widely used as colorant in foods, textiles, drugs and cosmetics. It is highly toxic, causes various types of allergies, thyroid activities, carcinogenicity, DNA damage behaviour, neurotoxicity and xenoestrogen nature in the humans and animals. The photochemical and biochemical degradation of the erythrosine is not recommended due to formation of toxic by-products. The present paper is an attempt to remove erythrosine from wastewater using adsorption over Bottom Ash-a power plant waste and De-Oiled Soya-an agricultural waste. Under the batch studies, effect of concentration of dye, temperature, pH of the solution, dosage of adsorbents, sieve size of adsorbents, etc., have been studied for the uptake of the dye over both adsorbents. The adsorption process verifies Langmuir and Freundlich adsorption isotherms in both the cases and based on the data different thermodynamic parameters have been evaluated. Batch studies also include kinetic measurements, rate constant study, mass transfer behaviour and establishment of mechanistic pathway for both the cases. For the bulk removal of the dye column operations have been carried out and breakthrough capacities of the Bottom Ash and De-Oiled Soya columns have been calculated. Attempts have also been made for the recovery of the adsorbed dye from exhausted columns by eluting dilute NaOH and more than 90% of the dye was recovered.

Adsorption↗

PubMed2006

Batch and bulk removal of hazardous dye, indigo carmine from wastewater through adsorption.

An inexpensive adsorption method has been developed for the removal of indigo carmine, a highly toxic indigoid class of dye from wastewater. Waste materials--bottom ash, a power plant waste and de-oiled soya, an agricultural waste--have been used as adsorbents. Attempts have been made through batch and bulk removal of the dye and both the adsorbents have been found to exhibit good efficiency to adsorb indigo carmine. Under batch technique effect of temperature, pH, concentration, dosage of adsorbents, sieve size of adsorbents, etc. have been observed. The dye uptake on to both the adsorbents is found to validate Langmuir and Freundlich adsorption isotherms models. Different thermodynamic parameters, like Gibb's free energy, enthalpy and entropy of the on-going adsorption process have also been evaluated. Batch technique has also been employed for the kinetic measurements and the adsorption follows a first order rate kinetics for both the adsorbents. The kinetic investigations also reveal for both the adsorbents film diffusion and particle diffusion mechanisms are operative in the lower and higher concentration ranges, respectively. Under the bulk removal, indigo carmine has been adsorbed through the column beds of bottom ash and de-oiled soya and more than 90% of the dye material has been recovered by eluting dilute NaOH solution through exhausted columns.

Adsorption↗

PubMed2005

Effect of EDTA and Fe-EDTA complex concentration on TCF Kraft mill effluent degradability. Batch and continuous treatments.

The effect of ethylenediaminetetracetic acid (EDTA) and Fe-EDTA complex on synthetic totally chlorine-free (TCF) effluent degradability in batch and continuously operating reactors was evaluated. Under batch treatment, the addition of EDTA and Fe-EDTA complex was studied in the range of 80 to 320 mg l(-1). Under continuously operated reactors, the Fe-EDTA complex concentration varied from 20 to 80 mg l(-1), and the hydraulic retention time (HRT) varied from 48 to 24 h. Sludge oxygen uptake rate (OUR) and chemical oxygen demand (COD) removal decreased when EDTA concentration increased in the influent under batch treatment; however, this inhibitory effect was reduced by the addition of Fe-EDTA complex. Without the addition of EDTA, COD removal decreased from 71% to 8%. The most efficient EDTA removal treatment (almost 10%) was the treatment of 80 mg l(-1) Fe-EDTA. Under continuously operated reactors, COD removal was greater than 57% in the synthetic TCF effluent with a Fe-EDTA concentration that varied from 20 to 80 mg l(-1); however, EDTA removal was lower than 25% in all cases. Synthetic TCF effluent with a Fe -EDTA concentration higher than 80 mg l(-1) could not be treated by the activated sludge treatment due to EDTA's inhibitory effect on the sludge.

Aerobiosis↗

PubMed2006

Effect of phosphate buffer concentration on the batch xylitol production by Candida guilliermondii.

AIMS: To evaluate the effect of phosphate buffer concentration on growth and xylitol production by Candida guilliermondii FTI 20037. METHODS AND RESULTS: Fermentations runs were carried out in batch mode employing semisynthetic medium supplemented with phosphate buffer at different concentrations (from 200 to 600 mmol l(-1)). The xylitol yield (Y(P/S)) and volumetric productivity (Q(P)) were improved when the fermentation medium was supplemented with phosphate buffer at concentration of 600 mmol l(-1). Under this condition (Y(P/S)) and (Q(P)) values were 0.75 g g(-1) and 0.66 g l(-1) h(-1), respectively, whereas in the absence of the phosphate buffer these values decreased to 0.52 g g(-1) and 0.44 g l(-1)h(-1) respectively. CONCLUSIONS: The use of phosphate buffer at 600 mmol l(-1) promoted an easier pH control during shake flasks fermentation of C. guilliermondii. In addition the xylitol yield and productivity were significantly improved in response to the supplementation of potassium phosphate in the medium. The increase in these parameters could be related to both osmotic effect and pH control. SIGNIFICANCE AND IMPACT OF THE STUDY: This approach provided a method for improving the xylitol production from semisynthetic medium by C. guilliermondii, being possible their use as a simple strategy to achieve efficient fermentation processes employing complex medium such as lignocellulosic hydrolysates.

Biomass↗

PubMed2006

Modeling chlorophenols degradation in sequencing batch reactors with instantaneous feed-effect of 2,4-DCP presence on 4-CP degradation kinetics.

Two instantaneously fed sequencing batch reactors (SBRs), one receiving 4-chlorophenol (4-CP) (SBR4) only and one receiving mixture of 4-CP and 2,4-dichlorophenol (2,4-DCP) (SBRM), were operated with increasing chlorophenols concentrations in the feed. Complete degradation of chlorophenols and high-Chemical oxygen demand (COD) removal efficiencies were observed throughout the reactors operation. Only a fraction of biomass (competent biomass) was thought to be responsible for the degradation of chlorophenols due to required unique metabolic pathways. Haldane model developed based on competent biomass concentration fitted reasonably well to the experimental data at different feed chlorophenols concentrations. The presence of 2,4-DCP competitively inhibited 4-CP degradation and its degradation began only after complete removal of 2,4-DCP. Based on the experimental results, the 4-CP degrader's fraction in SBRM was estimated to be higher than that in SBR4 since 2,4-DCP degraders were also capable of degrading 4-CP due to similarity in the degradation pathways of both compounds.

Chlorophenols↗

PubMed2003

[Effects of nutrient conditions and fed-batch culture on CoQ10 production by Rhizobium radiobacter WSH2601].

The effects of the variables, including the concentrations of glucose, sucrose, corn steep liquor (CSL) and peptone, and the conditions of fed-batch culture, on CoQ10 fermentation by Rhizobium radiobacter WSH2601 were assessed. The results showed that the optimum concentrations of glucose, sucrose, CSL and peptone were 30 g/L, 40 g/L, 11 g/L and 16 g/L respectively. Addition of CSL and tomato juice stimulated the cell growth. CSL, L-methionine and isopentyl alcohol efficiently increased the biosynthesis of CoQ10. In a 7L fermentor, the fed-batch culture improved both cell growth and CoQ10 production compared to a batch culture; and suitable mixed feeding of CSL and sucrose enhanced CoQ10 yield to 52.4 mg/L. The DCW reached 26.4 g/L, an increase of 53% in comparison to that without feeding, and an increase of 24% to that feeding with sucrose only. The C/B value reached 2.38 mg/g(DCW), representing an increase of 33% to that of without feeding, and an increase of 26% to that of feeding with sucrose only.

Agrobacterium tumefaciens↗

PubMed2000

Community dynamics of a mixed-bacterial culture growing on petroleum hydrocarbons in batch culture.

The effects of various hydrocarbon substrates, and a chemical surfactant capable of enhancing crude-oil biodegradation, on the community structure of a mixed-bacterial inoculum were examined in batch culture. Of 1000 TSA-culturable isolates, 68.6% were identified at the genus level or better by phospholipid fatty acid analysis over 7-day time course experiments. Cultures were exposed to 20 g/L Bow River crude oil with and without 0.625 g/L Igepal CO-630 (a nonylphenol ethoxylate surfactant), 5 g/L saturates, 5 g/L aromatics, or 125 g/L refinery sludge. A group of six genera dominated the cultures: Acinetobacter, Alcaligenes, Ochrobactrum, Pseudomonas/Flavimonas, Stenotrophomonas, and Yersinia. Species from four of the genera were shown to be capable of hydrocarbon degradation, and counts of hydrocarbon degrading and total heterotrophic bacteria over time were nearly identical. Pseudomonas/Flavimonas and Stenotrophomonas normally dominated during the early portions of cultures, although the lag phase of Stenotrophomonas appears to have been increased by surfactant addition. Acinetobacter calcoaceticus was the most frequently isolated microorganism during exposure to the saturate fraction of crude oil. Regardless of substrate, the culture medium supported a greater variety of organisms during the latter portions of cultures. Understanding the community structure and dynamics of mixed bacterial cultures involved in treatment of heterogeneous waste substrates may assist in process development and optimization studies.

Biodegradation, Environmental↗

PubMed2004

Molecular properties of ciprofloxacin-Indion 234 complexes.

The purpose of this research was to formulate tasteless complexes of ciprofloxacin with Indion 234 and to evaluate molecular properties of drug complexes. The effect of batch and column process, complexation time, temperature, and pH on ciprofloxacin loading on Indion 234 is reported. Drug resin complexes (DRC) were characterized by infrared spectroscopy, thermal analysis, and x-ray diffraction pattern. Ciprofloxacin release from DRC is obtained at salivary and gastric pH and in the presence of electrolytes. The efficient drug loading was evident in batch process using activated Indion 234 with a drug-resin ratio of 1:1.3. Drug complexation enhanced with pH from 1.2 to 6, while temperature did not affect the complexation process. Infrared spectroscopy revealed complexation of -NH (drug) with Indion 234. DRC are amorphous in nature. Drug release from DRC in salivary pH was insufficient to impart bitter taste. Volunteers rated the complex as tasteless and agreeable. Complete drug release was observed at gastric pH in 2 hours. The drug release was accelerated in the presence of electrolytes. Indion 234 is inexpensive, and the simple technique is effective for bitterness masking of ciprofloxacin.

Chemistry, Pharmaceutical↗

PubMed1984

Some effects of the essential fatty acids linoleic acid and alpha-linolenic acid and of their metabolites gamma-linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and of prostaglandins A1 and E1 on the proliferation of human osteogenic sarcoma cells in culture.

Gamma-linolenic acid has been shown to suppress the rate of proliferation of a number of malignant cell lines in culture. To test the proposal that this was a specific prostaglandin 1- or 2-series effect, 379 batches of MG63 human osteogenic sarcoma cells were seeded in Greiner flasks and cultured in media supplemented with a range of unsaturated fatty acids and prostaglandins. The monounsaturated fatty acid oleic acid enhanced the rate of cancer cell proliferation. The polyunsaturated fatty acids linoleic acid, gamma-linolenic acid, arachidonic acid, alpha-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid, as well as prostaglandins E1 and A1 suppressed the rate of cell proliferation. Total suppression of colony forming and cell proliferation occurred at high levels of polyunsaturated fatty acid supplementation. In addition gamma-linolenic in the form of evening primrose seed oil and vitamin C has been given to 6 patients with histologically diagnosed primary liver cell cancer. Some clinical improvement and reduction in tumor size occurred in 3 cases. One patient has shown remarkable improvement in reduction of liver and tumor size on the CAT scan and reduction of the serum alkaline phosphatase from 2830 to 295 units and gamma-glutamyl transaminase from 274 to 82 units. Thus preliminary clinical results suggest that gamma-linolenic acid may be effective in the management of human cancer patients and further trials should be conducted. However, the cell culture results suggest that although the essential fatty acids suppress proliferation, eicosanoids of all 3 series may be involved. The proliferation suppressive effect of docosahexaenoic acid suggests that other aspects than only eicosanoid activity may also be important in the suppression of cancer cell proliferation.

Alprostadil↗