Oral exposure to PAH: bioactivation processes in the human gut.
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Administration, Oral↗
Biomedical subjects
Willy Verstraete
Publications and source records attributed to Willy Verstraete.
Development of a sustainable treatment technology for domestic sewage.
We propose an integrated chemical-physical-biological treatment concept for the low-cost treatment of domestic wastewater. Domestic wastewater was subjected to a chemically enhanced primary sedimentation (CEPS), followed by treatment in an upflow anaerobic sludge blanket (UASB) reactor. In addition, a regenerable zeolite was used to remove NH4+, either after CEPS pretreatment or after biological treatment in the UASB reactor. The CEPS pretreatment consisted of the addition of a coagulant (FeCl3) and an anionic organic flocculant and removed on average 73% of the total chemical oxygen demand (CODt), 85% of the total suspended solids, and 80% of PO4(3-) present in the wastewater. The UASB system, which consequently received a low CODt input of approximately 140 mg/L, was operated using a volumetric loading rate of 0.4 g CODt/L.d (hydraulic retention time [HRT] = 10 h) and 0.7 g CODt/L.d (HRT = 5 h). For these conditions, the system removed about 55% of the CODt in its influent, thus producing an effluent with a low CODt of approximately 50 mg/L. The zeolite, when applied in batch mode before the UASB reactor, removed approximately 45% of the NH4+, whereas its application as a post-treatment cartridge resulted in almost 100% NH4+ removal. The simple design and relatively low operating costs, due to low costs of added chemicals and low energy input (estimated at Euro 0.07-0.1 per m3 wastewater treated), combined with excellent treatment performance, suggest that this system can be used as a novel domestic wastewater treatment system for developing countries. Therefore, the system is called a Low-cost, Integrated Sewage Treatment (LIST) system.
Animals↗
Anaerobic bioconversion of organic waste into biogas by hot water treatment at near-critical conditions: application in bioregenerative life support.
The feasibility of nearly-complete conversion of lignocellulosic waste (70% food crops, 20% faecal matter and 10% green algae) into biogas was investigated in the context of a Life Support Project. The treatment comprised a series of processes, i.e. a mesophilic laboratory scale CSTR (continuously stirred tank reactor), an upflow biofilm reactor and a hydrothermolysis system in near-critical water. By the one-stage CSTR, a biogas yield of 75% with a specific biogas production of 0.37 l biogas g(-1) VSS (volatile suspended solids) added at a HRT (hydraulic retention time) of 20 d was obtained. Biogas yields further increased with 10-15% at HRT > 20 d, indicating the hydrolysis of lignocellulose to be the rate-limiting conversion step. The solids present in the CSTR-effluent were subsequently treated by hot water treatment (T approximately 310-350 degrees C, p approximately 240 bar), resulting in effective carbon liquefaction (50-60% without and 83% with carbon dioxide saturation) and complete hygienisation of the residue. Subsequent anaerobic digestion of the hydrolysate allowed further conversion of 48-60% on COD (chemical oxygen demand) basis. Thus, the total process yielded biogas corresponding with a COD conversion up to 90% of the original organic matter. It appears that mesophilic digestion in conjunction with hydrothermolysis at near-critical conditions offers interesting features for (nearly) complete, non-toxic and hygienic carbon and energy recovery from human waste in a bioregenerative life support context.
Anaerobiosis↗
Bioaugmenting bioreactors for the continuous removal of 3-chloroaniline by a slow release approach.
The survival and activity of microbial degradative inoculants in bioreactors is critical to obtain successful biodegradation of non- or slowly degradable pollutants. Achieving this in industrial wastewater reactors is technically challenging. We evaluated a strategy to obtain complete and stable bioaugmentation of activated sludge, which is used to treat a 3-chloroaniline (3-CA) contaminated wastewater in a lab-scale semi-continuous activated sludge system. A 3-CA metabolizing bacterium, Comamonas testosteroni strain I2, was mixed with molten agar and encapsulated in 4 mm diameter open-ended silicone tubes of 3 cm long. The tubes containing the immobilized bacteria represented about 1% of the volume of the mixed liquor. The bioaugmentation activity of a reactor containing the immobilized cells was compared with a reactor with suspended I2gfp cells. From day 25-30 after inoculation, the reactor with only suspended cells failed to completely degrade 3-CA because of a decrease in metabolic activity. In the reactors with immobilized cells, however, 3-CA continued to be removed. A mass balance indicated that ca. 10% of the degradation activity was due to the immobilized cells. Slow release of the growing embedded cells from the agar into the activated sludge medium, resulting in a higher number of active 3-CA-degrading I2 cells, was responsible for ca. 90% of the degradation. Our results demonstrate that this simple immobilization procedure was effective to maintain a 3-CA-degrading population within the activated sludge community.
Aniline Compounds↗
Comparison of five in vitro digestion models to study the bioaccessibility of soil contaminants.
Soil ingestion can be a major exposure route for humans to many immobile soil contaminants. Exposure to soil contaminants can be overestimated if oral bioavailability is not taken into account. Several in vitro digestion models simulating the human gastrointestinal tract have been developed to assess mobilization of contaminants from soil during digestion, i.e., bioaccessibility. Bioaccessibility is a crucial step in controlling the oral bioavailability for soil contaminants. To what extent in vitro determination of bioaccessibility is method dependent has, until now, not been studied. This paper describes a multi-laboratory comparison and evaluation of five in vitro digestion models. Their experimental design and the results of a round robin evaluation of three soils, each contaminated with arsenic, cadmium, and lead, are presented and discussed. A wide range of bioaccessibility values were found for the three soils: for As 6-95%, 1-19%, and 10-59%; for Cd 7-92%, 5-92%, and 6-99%; and for Pb 4-91%, 1-56%, and 3-90%. Bioaccessibility in many cases is less than 50%, indicating that a reduction of bioavailability can have implications for health risk assessment. Although the experimental designs of the different digestion systems are distinct, the main differences in test results of bioaccessibility can be explained on the basis of the applied gastric pH. High values are typically observed for a simple gastric method, which measures bioaccessibility in the gastric compartment at low pHs of 1.5. Other methods that also apply a low gastric pH, and include intestinal conditions, produce lower bioaccessibility values. The lowest bioaccessibility values are observed for a gastrointestinal method which employs a high gastric pH of 4.0.
Biological Availability↗
Determination of phosphine in biogas and sludge at ppt-levels with gas chromatography-thermionic specific detection.
A gas chromatographic (GC) system to measure free phosphine in biogas and matrix bound phosphine in manure and sludge is presented. The system consists of a sample preconcentration trap filled with glass beads, connected with a capillary GC equipped with a thermionic specific detector. With a trap temperature as low as -155 degrees C, a sampling flow of 20 ml/min and a typical total sample volume of 100 ml, free phosphine concentrations in the low ng/m3 range and matrix bound phosphine in the low ng/kg dry matter range, can be accurately and reproducibly determined.
Chromatography, Gas↗
Optimisation and validation of an angiotensin-converting enzyme inhibition assay for the screening of bioactive peptides.
Angiotensin-converting enzyme (ACE) plays a major role in the regulation of blood pressure. A diagnostic assay to measure angiotensin-converting enzyme (ACE) activity was transformed into an enzyme inhibition assay and optimised, which led to a more sensitive and less expensive assay. By this spectrophotometric method, ACE inhibition is measured using the substrate furanacryloyl-Phe-Gly-Gly and as ACE source rabbit lung acetone extract. The optimised as well as the original ACE inhibition assay were used to verify the ACE inhibitory activity of captopril. The ACE inhibition assay was further validated by enalapril, its active derivative enalaprilat and the ACE-inhibitory peptide Ala-Leu-Pro-Met-His-Ile-Arg, corresponding to a tryptic fragment of bovine beta-lactoglobulin. Sigmoid curves could be fit adequately to the data points representing ACE inhibition in function of inhibitor concentration. IC(50) values for these compounds corresponded well with literature data. Furthermore, pea and whey protein hydrolysates obtained by digestion with trypsin showed ACE inhibitory activity in the ACE inhibition assay. Hence, this optimised assay is suitable to screen for ACE inhibitory peptides derived from food proteins with a possible antihypertensive effect in vivo.
Acetone↗
Changes in the microbiology of activated sludge upon the addition of iron salts with or without nitrite or nitrate.
Iron salts are frequently used in activated sludge treatment as coagulants or to improve reactor performance. However, the effect of the iron salts on the microbiology has received little attention. Furthermore, the interaction of iron ions with nitrite or nitrate present in the sludge has not been considered. In this research, the influence of ferrous and ferric iron additions, and their possible interactions with nitrite or nitrate at levels of a few mM, on the activated sludge microbiology of semi-continuous bench-scale reactors were examined. Conventional as well as molecular techniques have been used to investigate the microbial communities. Microscopic investigations showed that repeated addition of ferric iron at 2 mM gave rise to breaking of the sludge flocs, resulting in massive growth of sessile-protozoa and lowering of the numbers of nitrifiers. Ferrous iron at the same dosage resulted in large coherent flocs. Nitrite hereby seemed to enhance the detrimental effect of the ferric iron on the floc structure, whereas nitrate had a neutralizing character. 16S rRNA gene analysis showed a clear impact of the different iron respectively nitrogen treatments on the composition of bacterial communities. Cloning the sludge samples revealed the increased presence of denitrifying Feoxidizing bacteria in both the Fe(II) and Fe(III) reactors, suggesting a redox-state cycling between Fe(II) and Fe(III) in the mixed liquor.
Bacteria↗
Angiotensin-I Converting Enzyme (ACE) inhibitory peptides derived from pea and whey protein.
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Angiotensin-Converting Enzyme Inhibitors↗
In vitro and in vivo assessment of intraintestinal bacteriotherapy in chronic kidney disease.
Chronic kidney disease may progress to end-stage renal disease, which requires dialysis or kidney transplantation. No generally applicable therapies to slow progression of renal disease are available. Bacteriotherapy affords a promising approach to mitigate uremic intoxication by ingestion of live microbes able to catabolize uremic solutes in the gut. The present study evaluates the nonpathogenic soil-borne alkalophilic urease-positive bacterium Sporosarcina pasteurii (Sp) as a potential urea-targeted component for such "enteric dialysis" formulation. Data presented herein suggest that Sp survives through exposure to gastric juice retaining the ability to hydrolyze urea. In vitro, 10 cfu (colony forming units) of Sp removed from 21 +/- 4.7 mg to 228 +/- 6.7 mg urea per hour, depending on pH, urea concentration, and nutrient availability. Beneficial effects of Sp on fermentation parameters in the intestine were demonstrated in vitro in the Simulator of the Human Intestinal Microbial Ecosystem (SHIME) inoculated with fecal microbiota. Enumeration of marker organisms suggested that presence of Sp does not disturb microbial community of the SHIME. Additionally, a pilot study in 5/6th nephrectomized rats fed 10 cfu of live Sp daily throughout the study demonstrated that the tested regimen reduced blood urea-nitrogen levels and significantly prolonged the lifespan of uremic animals.
Animals↗
Polycyclic aromatic hydrocarbon release from a soil matrix in the in vitro gastrointestinal tract.
Soil ingestion is an important exposure route by which immobile soil contaminants enter the human body. We assessed polycyclic aromatic hydrocarbon (PAH) release from a contaminated soil, containing 49 mg PAH kg(-1), using a SHIME (Simulator of the Human Intestinal Microbial Ecosystem) reactor comprising the stomach, duodenal, and colon compartments. Polycyclic aromatic hydrocarbon release was defined as that fraction remaining in the digest supernatant after centrifugation for 5 min at 1500 x g. The PAH release in the stomach digest was only 0.44% of the total PAH present in soil, resulting in PAH concentrations of 23 micrograms PAH L(-1) chyme. The lower PAH releases in duodenum (0.13%) and colon (0.30%) digests, compared with the stomach digest, were thought to be attributed to combined complexation and precipitation with bile salts, dissolved organic matter, or colon microbiota. We studied these complexation processes in an intestinal suspension more in depth by preparing mixtures of 9-anthracenepropionic acid, a Bacillus subtilis culture, and cholin as model compounds for PAHs, organic matter, and bile salts, respectively. Bile salts or organic matter in the aqueous phase initially enhance PAH desorption from soil. However, desorbed PAHs may form large aggregates with bile and organic matter, lowering the freely dissolved PAH fraction in the supernatant. Using the model compounds, mathematical equations were developed and validated to predict PAH complexation processes in the gastrointestinal tract. Contaminant release and subsequent complexation in the gut is an important prerequisite to intestinal absorption and thus bioavailability of that contaminant. The data from this research may help in understanding the processes to which PAHs are subjected in the gastrointestinal tract, before intestinal absorption.
Absorption↗