Macro-kinetic investigation on phenol uptake from air by biofiltration: Influence of superficial gas flow rate and inlet pollutant concentration

The macro-kinetic behavior of phenol removal from a synthetic exhaust gas was investigated theoretically as well as experimentally by means of two identical continuously operating laboratory-scale biological filter bed columns. A mixture of peat and glass beads was used as filter material. After sterilization it was inoculated with a pure strain of Pseudomonas putida, as employed in previous experimental studies. To determine the influence of the superficial gas flow rate on biofilter performance and to evaluate the phenol concentration profiles along the column, two series of continuous tests were carried out varying either the inlet phenol concentration, up to 1650 mg . m(-3), or the superficial gas flow rate, from 30 to 460 m(3) . m(-2) . h(-1). The elimination capacity of the biofilter is proved by a maximum volumetric phenol removal rate of 0.73 kg . m(-3) . h(-1). The experimental results are consistent with a biofilm model incorporating first-order substrate elimination kinetics. The model may be considered a useful tool in scaling-up a biofiltration system. Furthermore, the deodorization capacity of the biofilter was investigated, at inlet phenol concentrations up to 280 mg . m(-3) and superficial gas flow rates ranging from 30 to 92 m(3) . m(-2) . h(-1). The deodorization of the gas was achieved at a maximum inlet phenol concentration of about 255 mg . m(-3), operating at a superficial gas flow rate of 30 m(3) . m(-2) . h(-1). (c) 1996 John Wiley & Sons, Inc.     

Improvement of homologous GH10 xylanase production by deletion of genes with predicted function in the Aspergillus nidulans secretion pathway

Filamentous fungi are important cell factories for large-scale enzyme production. However, production levels are often low, and this limitation has stimulated research focusing on the manipulation of genes with predicted function in the protein secretory pathway. This pathway is the major route for the delivery of proteins to the cell exterior, and a positive relationship between the production of recombinant enzymes and the unfolded protein response (UPR) pathway has been observed. In this study, Aspergillus nidulans was exposed to UPR-inducing chemicals and differentially expressed genes were identified by RNA-seq. Twelve target genes were deleted in A. nidulans recombinant strains producing homologous and heterologous GH10 xylanases. The knockout of pbnA (glycosyltransferase), ydjA (Hsp40 co-chaperone), trxA (thioredoxin) and cypA (cyclophilin) improved the production of the homologous xylanase by 78, 171, 105 and 125% respectively. Interestingly, these deletions decreased the overall protein secretion, suggesting that the production of the homologous xylanase was specifically altered. However, the production of the heterologous xylanase and the secretion of total proteins were not altered by deleting the same genes. Considering the results, this approach demonstrated the possibility of rationally increase the production of a homologous enzyme, indicating that trxA, cypA, ydjA and pbnA are involved in protein production by A. nidulans.     

Lipopolysaccharide reduces urethral smooth muscle contractility via cyclooxygenase activation

Journal of Physiology and Biochemistry - Lipopolysaccharide (LPS) is a component of gram-negative bacteria wall that elicits inflammatory response in the host through the toll-like receptor 4...     

Relationship between ventilatory threshold and muscle fiber conduction velocity responses in trained cyclists

The relationship between surface electromyography (SEMG) amplitude and the ventilatory threshold has been extensively studied. However, previous studies of muscle fiber conduction velocity (MFCV) are scarce and present insufficient evidence concerning the relationship between MFCV and metabolic responses during cycling. Based on that fact, the purpose of this study is twofold: (1) to investigate the existence of a MFCV threshold (MFCVT) during cycling and (2) to verify if this possible breakpoint is correlated with the ventilatory threshold (VT) and the SEMG threshold (SEMGT). Eight trained male cyclists (age 36.0 ± 9.7 years) performed an incremental cycling test with initial workload of 150 W gradually incremented by 20 W min^?1 until the exhaustion. Gas analyses were conducted using a breath-by-breath open-circuit spirometry and SEMG were registered from vastus lateralis in each pedaling cycle with a linear array of electrodes. A bi-segmental linear regression computer algorithm was used to estimate VT, MFCVT and SEMGT respectively in the carbon dioxide production (VCO₂), MFCV and electromyography root mean square (EMG RMS) curves. The one way ANOVA for repeated measures did not reveal any significant difference among VT (77.1 ± 7.5% of VO₂max), MFCVT (80.3 ± 10.4% of VO₂max) and SEMGT (81.9 ± 11.7% of VO₂max). The Bland and Altman procedure confirmed a good concordance between SEMGT and VT (Bias = 5.5 of %VO₂max) as well as MFCVT and VT (Bias = 5.2 of %VO₂max). The present findings suggest that muscle fiber conduction velocity threshold is a valid and reliable non-invasive tool to obtain information about ventilatory threshold in trained cyclists.     

Structural and Physiological Analyses of the Alkanesulphonate-Binding Protein (SsuA) of the Citrus Pathogen Xanthomonas citri

Background

The uptake of sulphur-containing compounds plays a pivotal role in the physiology of bacteria that live in aerobic soils where organosulfur compounds such as sulphonates and sulphate esters represent more than 95% of the available sulphur. Until now, no information has been available on the uptake of sulphonates by bacterial plant pathogens, particularly those of the Xanthomonas genus, which encompasses several pathogenic species. In the present study, we characterised the alkanesulphonate uptake system (Ssu) of Xanthomonas axonopodis pv. citri 306 strain (X. citri), the etiological agent of citrus canker.

Methodology/Principal Findings

A single operon-like gene cluster (ssuEDACB) that encodes both the sulphur uptake system and enzymes involved in desulphurisation was detected in the genomes of X. citri and of the closely related species. We characterised X. citri SsuA protein, a periplasmic alkanesulphonate-binding protein that, together with SsuC and SsuB, defines the alkanesulphonate uptake system. The crystal structure of SsuA bound to MOPS, MES and HEPES, which is herein described for the first time, provides evidence for the importance of a conserved dipole in sulphate group coordination, identifies specific amino acids interacting with the sulphate group and shows the presence of a rather large binding pocket that explains the rather wide range of molecules recognised by the protein. Isolation of an isogenic ssuA-knockout derivative of the X. citri 306 strain showed that disruption of alkanesulphonate uptake affects both xanthan gum production and generation of canker lesions in sweet orange leaves.

Conclusions/Significance

The present study unravels unique structural and functional features of the X. citri SsuA protein and provides the first experimental evidence that an ABC uptake system affects the virulence of this phytopathogen.     

Reproductive system morphology of Lightiella magdalenina (Crustacea,Cephalocarida): functional and adaptive implications

The reproductive systems of adults and larvae of Lightiella magdalenina were examined. Lightiella magdalenina, similar to the best-known cephalocarida species Hutchinsoniella macracantha, is a simultaneous hermaphrodite. Although the morphology of their reproductive system is similar, L. magdalenina differs from H. macracantha in exhibiting reduced fecundity: it lays one egg, not two, per reproductive event. This is due to asynchronous development of the oocytes inside the paired female reproductive structures, which determines the maturation of a single egg at a time. The reduced fecundity of L. magdalenina could be offset by the precocious release of oocytes from the germarium, which begins the vitellogenetic process during the last larval stages. Due to this process, after their last moult, reproductive adults can have a large number of advanced vitellogenic oocytes, reducing the time required for their maturation. A possible adaptive relationship between the halved fecundity with pre- and post-hatching parental care is discussed.     

Opposite Effect of Mast Cell Stabilizers Ketotifen and Tranilast on the Vasoconstrictor Response to Electrical Field Stimulation in Rat Mesenteric Artery

Objectives

We analyzed whether mast cell stabilization by either ketotifen or tranilast could alter either sympathetic or nitrergic innervation function in rat mesenteric arteries.

Methods

Electrical field stimulation (EFS)-induced contraction was analyzed in mesenteric segments from 6-month-old Wistar rats in three experimental groups: control, 3-hour ketotifen incubated (0.1 αmol/L), and 3-hour tranilast incubated (0.1 mmol/L). To assess the possible participation of nitrergic or sympathetic innervation, EFS contraction was analyzed in the presence of non-selective nitric oxide synthase (NOS) inhibitor L-NAME (0.1 mmol/L), α-adrenergic receptor antagonist phentolamine (0.1 µmol/L), or the neurotoxin 6-hydroxydopamine (6-OHDA, 1.46 mmol/L). Nitric oxide (NO) and superoxide anion (O₂ ^.-) levels were measured, as were vasomotor responses to noradrenaline (NA) and to NO donor DEA-NO, in the presence and absence of 0.1 mmol/L tempol. Phosphorylated neuronal NOS (P-nNOS) expression was also analyzed.

Results

EFS-induced contraction was increased by ketotifen and decreased by tranilast. L-NAME increased the vasoconstrictor response to EFS only in control segments. The vasodilator response to DEA-NO was higher in ketotifen- and tranilast-incubated segments, while tempol increased vasodilator response to DEA-NO only in control segments. Both NO and O₂ ^- release, and P-nNOS expression were diminished by ketotifen and by tranilast treatment. The decrease in EFS-induced contraction produced by phentolamine was lower in tranilast-incubated segments. NA vasomotor response was decreased only by tranilast. The remnant vasoconstriction observed in control and ketotifen-incubated segments was abolished by 6-OHDA.

Conclusion

While both ketotifen and tranilast diminish nitrergic innervation function, only tranilast diminishes sympathetic innnervation function, thus they alter the vasoconstrictor response to EFS in opposing manners.