Assessing the role of feed water constituents in irreversible membrane fouling of pilot-scale ultrafiltration drinking water treatment systems.

Fluorescence excitation-emission matrix (EEM) approach together with principal component analysis (PCA) was used for assessing hydraulically irreversible fouling of three pilot-scale ultrafiltration (UF) systems containing full-scale and bench-scale hollow fiber membrane modules in drinking water treatment. These systems were operated for at least three months with extensive cycles of permeation, combination of back-pulsing and scouring and chemical cleaning. The principal component (PC) scores generated from the PCA of the fluorescence EEMs were found to be related to humic substances (HS), protein-like and colloidal/particulate matter content. PC scores of HS- and protein-like matter of the UF feed water, when considered separately, showed reasonably good correlations with the rate of hydraulically irreversible fouling for long-term UF operations. In contrast, comparatively weaker correlations for PC scores of colloidal/particulate matter and the rate of hydraulically irreversible fouling were obtained for all UF systems. Since, individual correlations could not fully explain the evolution of the rate of irreversible fouling, multi-linear regression models were developed to relate the combined effect of HS-like, protein-like and colloidal/particulate matter PC scores to the rate of hydraulically irreversible fouling for each specific UF system. These multi-linear regression models revealed significant individual and combined contribution of HS- and protein-like matter to the rate of hydraulically irreversible fouling, with protein-like matter generally showing the greatest contribution. The contribution of colloidal/particulate matter to the rate of hydraulically irreversible fouling was not as significant. The addition of polyaluminum chloride, as coagulant, to UF feed appeared to have a positive impact in reducing hydraulically irreversible fouling by these constituents. The proposed approach has applications in quantifying the individual and synergistic contribution of major natural water constituents to the rate of hydraulically irreversible membrane fouling and shows potential for controlling UF irreversible fouling in the production of drinking water.

Identification of humic acid-like and fulvic acid-like natural organic matter in river water using fluorescence spectroscopy.

Identifying the extent of humic acid (HA)-like and fulvic acid (FA)-like natural organic matter (NOM) present in natural water is important to assess disinfection by-product formation and fouling potential during drinking water treatment applications. However, the unique fluorescence properties related to HA-like NOM is masked by the fluorescence signals of the more abundant FA-like NOM. For this reason, it is not possible to accurately characterize HA-like and FA-like NOM components in a single water sample using direct fluorescence EEM analysis. A relatively simple approach is described here that demonstrates the feasibility of using a fluorescence excitation-emission matrix (EEM) approach for identifying HA-like and FA-like NOM fractions in water when used in combination with a series of pH adjustments and filtration steps. It is demonstrated that the fluorescence EEMS of HA-like and FA-like NOM fractions from the river water sample possessed different spectral properties. Fractionation of HA-like and FA-like NOM prior to fluorescence analysis is therefore proposed as a more reasonable approach.

Acquiring reproducible fluorescence spectra of dissolved organic matter at very low concentrations.

A method that would allow for fast and reliable measurements of dissolved organic matter (DOM), both at low and high concentration levels would be a valuable tool for online monitoring of DOM. This could have applications in a variety of areas including membrane treatment systems for drinking water applications which is of interest to our group. In this study, the feasibility of using fluorescence spectroscopy for monitoring DOM at very low concentration levels was demonstrated with an emphasis on optimizing the instrument parameters necessary to obtain reproducible fluorescence signals. Signals were acquired using a cuvette or a fibre optic probe assembly, the latter which may have applications for on-line or in-line monitoring. The instrument parameters such as photomultiplier tube (PMT) voltage, scanning rate and slit width were studied in detail to find the optimum parameter settings required. The results showed that larger excitation and emission slit widths were preferred, over larger PMT voltage or lower scanning rates, to obtain reproducible and rapid measurements when measuring very low concentration levels of DOM. However, this approach should be implemented with caution to avoid any reduction of the signal resolution.

Decolorization potential of mixed microbial consortia for reactive and disperse textile dyestuffs.

Four different aerobic mixed consortia collected from basins of wastewater streams coming out of dying plants of Crescent Textile (CT), Sitara Textile (ST), Chenab Fabrics (CF) and Noor Fatima Textile (NF), Faisalabad, Pakistan were applied for decolorization of Drimarene Orange K-GL, Drimarene Brilliant Red K-4BL, Foron Yellow SE4G and Foron Blue RDGLN for 10 days using the shake flask technique. CT culture showed the best decolorization potential on all dyestuffs followed by ST, NF and CF, respectively. CT could completely decolorize all dyes within 3-5 days. ST cultures showed effective decolorization potential on Foron Yellow SE4G and Drimarene Brilliant Red K-4BL but complete color removal was achieved after 4 and 7 days, respectively. NF culture showed 100% decolorization efficiencies on Foron Yellow SE4G and Foron Blue RDGLN but it took comparatively longer time periods (5-7 days). Where as, the NF culture had decolorized only 40% and 50% of Drimarene orange and red, respectively, after 10 days. CF caused complete decolorization of Foron Blue RDGLN and Drimarene Brilliant Red K-4BL after 4 and 8 days, respectively but it showed poor performance on other two dyes.

CDH23 mutation and phenotype heterogeneity: a profile of 107 diverse families with Usher syndrome and nonsyndromic deafness.

Usher syndrome type I is characterized by congenital hearing loss, retinitis pigmentosa (RP), and variable vestibular areflexia. Usher syndrome type ID, one of seven Usher syndrome type I genetic localizations, have been mapped to a chromosomal interval that overlaps with a nonsyndromic-deafness localization, DFNB12. Mutations in CDH23, a gene that encodes a putative cell-adhesion protein with multiple cadherin-like domains, are responsible for both Usher syndrome and DFNB12 nonsyndromic deafness. Specific CDH23 mutational defects have been identified that differentiate these two phenotypes. Only missense mutations of CDH23 have been observed in families with nonsyndromic deafness, whereas nonsense, frameshift, splice-site, and missense mutations have been identified in families with Usher syndrome. In the present study, a panel of 69 probands with Usher syndrome and 38 probands with recessive nonsyndromic deafness were screened for the presence of mutations in the entire coding region of CDH23, by heteroduplex, single-strand conformation polymorphism, and direct sequence analyses. A total of 36 different CDH23 mutations were detected in 45 families; 33 of these mutations were novel, including 18 missense, 3 nonsense, 5 splicing defects, 5 microdeletions, and 2 insertions. A total of seven mutations were common to more than one family. Numerous exonic and intronic polymorphisms also were detected. Results of ophthalmologic examinations of the patients with nonsyndromic deafness have found asymptomatic RP-like manifestations, indicating that missense mutations may have a subtle effect in the retina. Furthermore, patients with mutations in CDH23 display a wide range of hearing loss and RP phenotypes, differing in severity, age at onset, type, and the presence or absence of vestibular areflexia.

Fragrance volatiles of developing and senescing carnation flowers.

Thirteen major volatiles of the carnation flower fragrance signature have been identified by GC/MS. Of these, ten, hexanal, (2E)-hexenal, 1-hexanol, 2-hexanol, 3-hexen-1-ol, nonanal, benzaldehyde, benzyl alcohol, benzyl benzoate and caryophyllene, were quantified. The steady-state levels of these ten volatiles change independently as the flowers develop and senesce, suggesting that their synthesis is developmentally regulated. In addition, the chemical composition of the fragrance signature in naturally senesced flowers proved to be very different from that for flowers that had been induced to senesce prematurely by treatment with ethylene. Thus, senescence-related changes in carnation floral scent appear not to be directly regulated by ethylene. From cellular fractionation studies, it is evident that all of the volatiles, except 2-hexanol, are present in both membranous and cytosolic compartments, suggesting that their synthesis is membrane-associated and that they subsequently partition into the cytosol in accordance with partition coefficients.

Production of tomato flavor volatiles from a crude enzyme preparation using a hollow-fiber reactor.

In recent years there has been an increase in the interest in the production of compounds by isolation from natural sources or through processes that can be deemed "natural". This is of particular interest in the food and beverage industry for flavors and aromas. Hexanal, organoleptically known to possess "green character", is of considerable commercial interest. The objective of this study was to determine if the enzyme template known to be responsible for the synthesis of hexanal from linoleic acid (18:2) in tomato fruits could be harnessed using a hollow-fiber reactor. A hollow-fiber reactor system was set up and consisted of a XAMPLER ultrafiltration module coupled to a reservoir. The enzyme template was extracted from ripe tomato fruits and processed through an ultrafiltration unit (NMWC of 100 kDa) to produce a retentate enriched in soluble and membrane-associated lipoxygenase (LOX) and hydroperoxide lyase (HPL). This extract was recirculated through the lumen of the hollow-fiber ultrafiltration unit with the addition of substrate in the form of linoleic acid, with buffer addition to the reaction flask to maintain a constant retentate volume. Product formation was measured in the permeate using solid phase microextraction (SPME) developed for this system. At exogenous substrate concentrations of 16 mM and a transmembrane pressure of 70 kPa, hexanal production rates are in the order of 5.1 microg/min. Addition of Triton X-100 resulted in membrane fouling and reduced flux. The reactor system has been run for periods of up to 1 week and has been shown to be stable over this period.

Characterization and regulation of catabolic genes.

Although a wide range of microorganisms have been discovered that are able to degrade highly stable, toxic xenobiotics, still many pollutants persist in the environment. Recent advances in the field of r-DNA technology has provided solutions to these problems. One important factor limiting the bioremediation of sites contaminated with certain hazardous wastes is the slow rate of degradation. This slow rate limits the practicality of using bacteria in remediating contaminated sites. It is possible to extend the range of substrates that an organism can utilize. It is even possible to endow an organism with the ability to degrade a predetermined range of xenobiotics. Because biotechnological processes are based on natural activities of microorganisms and constitute variations in classic domestic waste treatment processes, they are publicly more accepted. This is an area where genetic engineering can make a marked improvement by manipulating catabolic genes of microorganisms. Advances in r-DNA technology have opened up new avenues to move toward the goal of genetically engineered microorganisms to function as "designer biocatalysts" in which certain desirable biodegradation pathways or enzymes from different organisms are brought together in a single host with the aim of performing specific detoxification. In the last 2 decades much progress has been made in this direction, and as a result catabolic genes have been cloned and characterized for organochlorines, polychlorinated biphenyls, chlorobenzoates, naphthalene etc. The aim of this review is to provide an insight in the recent advances made on characterization and expression of catabolic genes that encode the degradation/detoxification of these persistent and toxic xenobiotic compounds.

Retinal nerve fiber layer changes and visual field loss in idiopathic intracranial hypertension.

PURPOSE: The authors retrospectively analyzed changes in the retinal nerve fiber layer in patients with idiopathic intracranial hypertension and studied their relation to visual field loss to determine the clinical usefulness of retinal nerve fiber analysis in the clinical management of patients with papilledema. METHODS: Retinal nerve fiber layer photographs and visual fields from 36 eyes of 21 patients with papilledema due to idiopathic intracranial hypertension were analyzed for abnormalities in a masked fashion. RESULTS: Nerve fiber layer changes were found in 67% of eyes studied. Superior areas within the nerve fiber layer were affected 5.4 times more frequently than inferior regions. Visual field loss was more prevalent in eyes with diffuse nerve fiber layer loss (89%) than in eyes with slit defects (29%). The location of the nerve fiber layer changes correlated with corresponding areas of visual field loss. Nerve fiber layer changes were as common in mild to moderate as in atrophic papilledema; however, slit defects predominated in patients with mild to moderate papilledema, and diffuse loss predominated in atrophic papilledema. CONCLUSIONS: Changes in the retinal nerve fiber layer observed in patients with idiopathic intracranial hypertension provide objective information regarding the status of their optic nerve and may improve their clinical management.

Biodegradation and sorption of polyaromatic hydrocarbons by Phanerochaete chrysosporium.

The ability of the white-rot fungus Phanerochaete chrysosporium (INA-12) to degrade various polynuclear aromatic hydrocarbons (PAH) was investigated. Under static, non-nitrogen-limiting conditions, P. chrysosporium mineralized both phenanthrene and benzo[a]pyrene. Total mineralization, based on radioactive tracing, was limited to 1.8%-3% for phenanthrene and benzo[a]pyrene respectively. In both cases the pattern of mineralization did not correlate temporally with the production of lignin peroxidase activity. Sorption of radiolabelled material to the biomass was very significant with 22% and 40% of the total radioactivity being sorbed for benzo[a]pyrene and phenanthrene respectively. A number of models were examined to predict the sorption isotherms, the best performance being obtained with a three-parameter empirical model. It is apparent that lignin peroxidase is not necessarily involved in the biodegradation of all PAH and that a significant factor in PAH biodegradation and/or disappearance in cultures with the intact fungus may be attributed to sorption phenomena.

Microbial utilization of levoglucosan in wood pyrolysate as a carbon and energy source.

The Waterloo Fast Pyrolysis Process (WFPP) can produce an organic liquid high in levoglucosan (1, 6-anhydro-beta-D-glucopyranose) content from suitably pretreated lignocellulosics. A variety of fungi and yeasts were screened for their ability to utilize and ferment this organic liquid. To enhance its fermentability, the pyrolysis tar was posttreated in three different ways: (1) an aqueous extract (lignin removed); (2) activated charcoal treated (lignin and aromatics removed); and (3) acid hydrolysate (lignin and aromatics removed with the levoglucosan hydrolyzed to glucose). Four fungal strains were examined. None grew in the aqueous extract, but all grew equally well in both the activated charcoal treated and the acid hydrolysate, suggesting that the aromatic species were inhibitory to growth. Seven yeast species were examined, two of which did not grow on any of the extracts. Five of the yeast strains grew well on both the aqueous extract as well as the activated charcoal extract. The hydrolysate was optimal in terms of biomass yield and ethanol production. Ethanol yields on the hydrolysate were comparable or better than those on glucose. Ethanol was also produced in the aqueous extract and activated charcoal-treated substrate, but yields were considerably lower than on the hydrolysate or glucose. It is apparent that a wood pyrolysate maximized for levoglucosan can serve as a fermentable substrate, although postpyrolysis clean-up appears necessary.

Modelling the growth kinetics of Phanerochaete chrysosporium in submerged static culture.

The potential commercial application of Phanerochaete chrysosporium requires methods for quantitatively predicting growth and substrate utilization. The growth kinetics of P. chrysosporium INA-12 (CNCM I-398) were investigated and modelled under nonlimiting nitrogen and carbon conditions in submerged static culture. This strain, unlike other strains, does not require nutrient limitation for induction of lignin peroxidase. Maximum levels of lignin peroxidase activity were reached 7 days after culture initiation, when almost 80% of the initial glycerol and 70% of the initial nitrogen were still present. Lignin peroxidase levels then decreased, while biomass levels increased until about day 14. The ratio of cell dry weight to wet weight was constant until the maximum biomass concentration was achieved, after which there was a decrease in the water content. The change in this ratio reflects cell lysis as it correlated with increased concentrations of nitrogen in the media, arising from cell leakage. The suitability of four growth models to predict growth, and in some cases glycerol consumption, was evaluated. A simple linear model and the Emerson model performed poorly for the early stages of growth, while a modified Williams model and the Monod model predicted substrate and biomass concentrations equally well. All models will predict biomass concentrations during the active growth phase, but they should not be used to predict biomass concentrations after the stationary growth phase, when cell lysis becomes significant.

Enhanced biodegradation of phenanthrene in oil tar-contaminated soils supplemented with Phanerochaete chrysosporium.

In recent years, the white rot fungus Phanerochaete chrysosporium has shown promise as an organism suitable for the breakdown of a broad spectrum of environmental pollutants, including polynuclear aromatic hydrocarbons (PAHs). The focus of this study was to determine whether P. chrysosporium could effectively operate in an actual field sample of oil tar-contaminated soil. The soil was loaded with [14C]phenanthrene to serve as a model compound representative of the PAHs. Soil with the native flora present under static, aerobic conditions with buffering (pH 5.0 to 5.5) displayed full mineralization on the order of 20% in 21 days. The addition of P. chrysosporium was synergistic, with full mineralization on the order of 38% in 21 days. In addition to full mineralization, there was an increase in the proportion of radiolabelled polar extractives, both soluble and bound, in the presence of P. chrysosporium. From this study, it is apparent that the native soil microflora can be prompted into full mineralization of PAHs in some contaminated soils and that this mineralization can be enhanced when supplemented with the white rot fungus P. chrysosporium. With further refinement, this system may prove an effective bioremediation technology for soils contaminated with PAHs.

Periodic alternating gaze deviation in infancy.

Periodic alternating gaze is a rarely reported phenomenon. We have observed two cases that are unique in their early onset at birth and infancy. Multiple congenital defects of the posterior cranial fossa were present on MRI in both cases. A prominent abnormality shared by both was absence of normal structures in the region of the inferior cerebellar vermis. Periodic alternating gaze appears to be associated with pathologic changes in the hindbrain in these and other reported cases.

Development of a multienzyme reactor for dopamine synthesis: II. Reactor engineering and simulation.

Aspects of reaction engineering associated with multienzyme reactions have been studied in a system where dopamine is produced from catechol, pyruvate and ammonium by sequential enzymatic reactions catalyzed by tyrosine phenol lyase (TPL) and tyrosine decarboxylase (TDC). Microbial cells containing TPL activity (Erwinia herbicola) and TDC activity (Streptococcus faecalis) were coimmobilized in glutaraldehyde cross-linked porcine gelatin beads with a mean diameter of 2.8 mm for use in the reactions. Measurement of the transport properties in the beads indicate that the gelatin matrix does not significantly increase the diffusion resistance and that dopamine partitions into the matrix (K = 2). A packed-bed reactor containing the coimmobilized cell beads successfully produced dopamine, although with a low conversion. Using computer simultaneous it is shown that separate, sequential TPL and TDC, rather than simultaneous, reactions, would require smaller reactors overall for the same conversion.

Hypertropia following trochlear trauma.

Hypertropia following trauma to the trochlea is rare. The more widely recognized response of the trochlea to trauma is hypotropia or acquired Brown syndrome. We observed three cases of hypertropia following penetrating trauma to the trochlea. Each had computerized tomography and/or magnetic resonance imaging to assist in the understanding of the mechanism of the observed superior oblique dysfunction. The clinical course of these cases was variable. Awareness of the damaged trochlea's capacity to respond as a hypertropic as well as a hypotropic syndrome will allow for improved management of these unusual patients.

Development of a multienzyme reactor for dopamine synthesis: I. enzymology and kinetics.

The enzymology and kinetics of tyrosine phenol lyase (TPL) from Erwinia herbicola, and tyrosine decarboxylase (TDC) from Streptococcus faecalis have been investigated for potential use in a coimmobilized multienzyme biocatalytic system for the production of dopamine. In this multienzyme biotransformation using whole cells optimized for each of the respective enzymes, TPL catalyzes the production of 3,4-dihydroxyphenyl-L-alanine (L-dopa) from catechol, pyruvate, and ammonium, and this is subsequently decarboxylated by TDC to produce dopamine. Performing the reactions simultaneously, thereby removing L-dopa, is one option for overcoming the TPL equilibrium constraints. The enzymes have different optimal pH values, so the reaction kinetics at a compromise pH of 7.1, where both enzymes could be operated simultaneously, were investigated. For the concentration range investigated, TPL followed pseudo-first-order kinetics with respect to catechol, pyruvate, and ammonium. TDC exhibited significant product inhibition as well as inhibition by combinations of catechol and pyruvate.

Biotransformation of dopamine to norlaudanosoline by Aspergillus niger.

Norlaundanosoline is a key intermediate in the synthesis of the benzylisoquinoline alkaloids providing the upper isoquinoline portion of the morphinan skeleton. This study evaluates the feasibility of using Aspergillus niger as an in situ biotransformation system to produce norlaudanosoline from dopamine. A. niger was chosen because monoamine oxidase can be readily induced in this organism. Monoamine oxidase catalyzes the conversion of dopamine to 3,4-dihydroxyphenylacetaldehyde. In the presence of dopamine, this aldehyde will then undergo a spontaneous Picket-Spengler condensation to form norlaudanosoline. Fermentation condition to form norlaudanosoline. Fermentation conditions were optimized for the production monoamine oxidase by using a two-stage process consisting of a growth stage and an induction stage. pH control was found to be important, and at pH 4.5 dopamine accumulation in the cells was high as was the level of monoamine oxidase. With pH control at 4.5, up to 21% of the cellular dopamine was converted to norlaudanosoline. It is proposed that with further protein engineering improvements, this system may prove suitable for the in situ bio-transformation of dopamine to norlaudanosoline.