Bioavailability of organic compounds solubilized in nonionic surfactant micelles

Whether direct availability of organic compound solubilized in nonionic surfactant micelles (bioavailability) in a bioremediation or biotransformation process is uncertain to some extent, which is partially attributed to the difficulty by direct experimental determination. In another point of view, it should be ascribed to the fuzzy concept about the solubilization of organic compound in a nonionic surfactant micelle aqueous solution. In this mini-review, the solubilization of organic compound in surfactant micelles aqueous solution is fully discussed; especially saturated solubilization and unsaturated solubilization have been emphasized. Then the current methods for estimation of bioavailability of organic compounds solubilized in micelles are introduced, in which the possible drawbacks of each method are stressed. Finally, the conclusion that organic compound solubilized in micelles is unavailable directly by microbes has been drawn and the intensification of bioremediation or biotransformation by nonionic surfactant micelle aqueous solution is contributed to enhancement of the hydrophobic organic compounds dissolution.     

Bioavailability of isoflavones

Isoflavones are disease protective components of soybeans. Isoflavone metabolism and bioavailability are key to understanding their biological effects. Isoflavone glucuronides, dominant biotransformation products in humans that are more hydrophilic than isoflavone aglycones, activate human natural killer cells in vitro but are less toxic to NK cells than the parent aglycones. Gut microbial isoflavone metabolites have also been identified, but remain to be well characterized. Gut transit time (GTT) seems to be a significant determinant of isoflavone bioavailability because women with more rapid GTT (<40 h) experienced 2-3-fold greater absorption of isoflavones than did women with longer GTT (>65 h). Isoflavone metabolism varies a great deal among individuals, thus limiting the quantitative value of urine or plasma isoflavones as biomarkers of soy ingestion. Defining and lessening interindividual variation in isoflavone bioavailability, and characterizing health-related effects of key isoflavone metabolites are likely to be crucial to further understanding of the health benefits of isoflavones.     

Bioavailability of phenolic acids

Two large classes of phenolic acids were comprised in this review: benzoic acid derivatives and cinnamic acid derivatives. They have been found to be very extended in fruits and vegetables at different concentrations. For example, hydroxycinnamic acids concentration was higher than that found for hydroxybenzoic acids. Concerning their consumption, hydroxycinnamic acids provide larger contributions to the total polyphenol intake than benzoic acid derivatives or flavonoids. This phenolic acid intake is led by the coffee intake since it has very rich concentrations in hydroxycinnamic acids. Moreover, several experimental and epidemiological studies report the protection of phenolic acids against various degenerative diseases. However, despite all these interesting attributions and even if phenolic acids are the main polyphenols consumed, their bioavailability has not received as attention as that flavonoids. This concept is an essential step to understand the health-promoting properties of phenolic acids and to serve as tool to design in vivo and in vitro experiments to know their biological properties. Therefore, a compilation of bioavailability data of phenolic acids have been presented here paying attention to the two types of phenolic acid bioavailability, direct and indirect derived from the direct phenolic acid and flavonoid consumption, respectively. Then, a new relevant concept which may be named as total bioavailability of phenolic acids includes the direct absorption and metabolism of phenolic acids from food consumption and phenolic acids bioavailability as a result of the cleavage on the main skeleton ring of flavonoids by the gut microflora.     

Bioavailability of Sorbed 3-Chlorodibenzofuran

One of the main factors impeding the bioremediation of polluted soils, sediments, and aquifers is the low bioavailability of chemicals which are sorbed by organic matter. To obtain more insight into the factors that control the degradation of sorbed compounds, we used a defined model system in which 3-chlorodibenzofuran (3CDF) was the organic contaminant, porous Teflon granules were the sorbent, and Sphingomonas sp. strain HH19k was the test organism. The sorption of 3CDF to Teflon reached equilibrium within 150 min. The curved shape of the sorption isotherm, the extent of sorption, and the desorption kinetics suggested that there was a surface interaction (adsorption) between 3CDF and Teflon which took place mainly inside the pores of the granules. The kinetics of desorption could be ascribed to sorption-retarded radial diffusion inside the granules since the desorption rate not only was correlated with the sorbed-phase concentration, but also depended on the equilibration status of sorption, since (i) the high initial desorption rate sharply declined because of the depletion of 3CDF in the outermost parts of the granules, but high rates were observed again after the system had been given time to reequilibrate, and (ii) the initial desorption rate was higher when the preceding contact time between sorbate and sorbent was shorter (i.e., most 3CDF was still located in the exterior parts of the granules). These characteristics were observed irrespective of whether the desorption was driven by percolating water through the sorbent or by attaching active bacteria to the sorbent. 3CDF consumption by attached cells drove 3CDF desorption to a considerable extent. The attached cells were thus efficiently supplied with desorbing 3CDF. On the basis of our results, we propose that the rate at which a sorbed substrate becomes available for organisms is influenced by (i) the specific affinity of the degrading organisms (i.e., their ability to reduce the aqueous substrate concentration) and (ii) the tendency of the organisms to adhere to the sorbent.     

Bioavailability of ampicillin suspensions]

The rate of ampicillin transfer into solution from suspensions of 2 types, i.e. suspensions of anhydrous ampicillin and suspensions of ampicillin trihydrate was studied. Conditions for estimation of the rate of ampicillin dissolution from the suspensions were developed. The pharmacokinetics of the pharmaceutical forms was studied on dogs. Definite advantages of the anhydrous ampicillin suspension were shown as compared to the ampicillin trihydrate suspension.     

Bioavailability of pollutants and chemotaxis

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Highlights► The exposure of bacteria to pollutants induces chemoattraction or chemorepellence. ► Pollutant chemoreceptors so far identified are present on plasmids. ► Chemotaxis increases pollutant bioavailability and enhances biodegradation rates. ► Chemotaxis may improve microbial inoculants designed just on catabolic potential.     

Bioavailability of organochlorines in fish

• 1.1. An overview is presented of the processs of chemical sorption and membrane permeation that control the bioavailability of organochlorines in natural waters.
• 2.2. The mechanisms of membrane permeation and chemical sorption to various types of dissolved and particulate matter is discussed and simple models are presented that can be used to estimate the bioavailability of organic chemicals in natural waters.

     

Assessment of Bioavailability of Soil-Sorbed Atrazine

Bioavailability of pesticides sorbed to soils is an important determinant of their environmental fate and impact. Mineralization of sorbed atrazine was studied in soil and clay slurries, and a desorption-biodegradation-mineralization (DBM) model was developed to quantitatively evaluate the bioavailability of sorbed atrazine. Three atrazine-degrading bacteria that utilized atrazine as a sole N source (Pseudomonas sp. strain ADP, Agrobacterium radiobacter strain J14a, and Ralstonia sp. strain M91-3) were used in the bioavailability assays. Assays involved establishing sorption equilibrium in sterile soil slurries, inoculating the system with organisms, and measuring the CO₂ production over time. Sorption and desorption isotherm analyses were performed to evaluate distribution coefficients and desorption parameters, which consisted of three desorption site fractions and desorption rate coefficients. Atrazine sorption isotherms were linear for mineral and organic soils but displayed some nonlinearity for K-saturated montmorillonite. The desorption profiles were well described by the three-site desorption model. In many instances, the mineralization of atrazine was accurately predicted by the DBM model, which accounts for the extents and rates of sorption/desorption processes and assumes biodegradation of liquid-phase, but not sorbed, atrazine. However, for the Houghton muck soil, which manifested the highest sorbed atrazine concentrations, enhanced mineralization rates, i.e., greater than those expected on the basis of aqueous-phase atrazine concentration, were observed. Even the assumption of instantaneous desorption could not account for the elevated rates. A plausible explanation for enhanced bioavailability is that bacteria access the localized regions where atrazine is sorbed and that the concentrations found support higher mineralization rates than predicted on the basis of aqueous-phase concentrations. Characteristics of high sorbed-phase concentration, chemotaxis, and attachment of cells to soil particles seem to contribute to the bioavailability of soil-sorbed atrazine.     

Bioavailability of glucosyl hesperidin in rats

Glucosyl hesperidin (G-hesperidin) is a water-soluble derivative of hesperidin. We compared the absorption and metabolism of G-hesperidin with those of hesperidin in rats. After oral administration of G-hesperidin or hesperidin to rats, hesperetin was detected in sera hydrolyzed with beta-glucuronidase, but it was not detectable in unhydrolyzed sera. Serum hesperetin was found more rapidly in rats administered G-hesperidin than in those administered hesperidin. The area under the concentration-time curve for hesperetin in the sera of rats administered G-hesperidin was approximately 3.7-fold greater than that of rats administered hesperidin. In the urine of both administration groups, hesperetin and its glucuronide were found. Urinary excretion of metabolites was higher in rats administered G-hesperidin than in those administered hesperidin. These results indicate that G-hesperidin presents the same metabolic profile as hesperidin. Moreover, it was concluded that G-hesperidin is absorbed more rapidly and efficiently than hesperidin, because of its high water solubility.     

Bioavailability of organochlorines in fish.

1. An overview is presented of the process of chemical sorption and membrane permeation that control the bioavailability of organochlorines in natural waters. 2. The mechanisms of membrane permeation and chemical sorption to various types of dissolved and particulate matter is discussed and simple models are presented that can be used to estimate the bioavailability of organic chemicals in natural waters.