Biomedical subjects

K Lacki

Publications and source records attributed to K Lacki.

4 recordsLinked to original sources

PubMed2001

Modeling and analysis of the dynamic behavior of mechanisms that result in the development of inner radial humps in the concentration of a single adsorbate in the adsorbed phase of porous adsorbent particles observed in confocal scanning laser microscopy experiments: diffusional mass transfer and adsorption in the presence of an electrical double layer.

A theoretical model for adsorption of a single charged adsorbate that accounts for the presence of an electrical double layer in the pores of adsorbent particles is constructed and solved. The dynamic behavior of the mechanisms of the model can result in the development of inner radial humps (concentration rings) in the concentration of a single charged analyte (adsorbate) in the adsorbed phase of porous adsorbent particles. The results of the present work demonstrate the implication of the concept regarding the effect of the presence of an electrical double layer in the pores of adsorbent particles and the induced interactions between the electrostatic potential distribution and the mechanisms of mass transport of the species by diffusion, electrophoretic migration, and adsorption. Furthermore, the mechanisms of the model could explain qualitatively the development of the concentration ring (hump) observed in confocal scanning laser microscopy experiments.

Adsorption↗

PubMed1999

A method for the decrease of phenolic content in commercial canola meal using an enzyme preparation secreted by the white-rot fungus Trametes versicolor.

An enzymatic process for upgrading the quality of canola meal (CM) by decreasing its phenolic content was investigated. The new method was based on the addition of the enzyme preparation from white-rot fungus Trametes versicolor to the meal-buffer slurry. A 98% decrease in the concentration of SAE was observed after 1 h of the treatment. The following process variables were considered for optimizing the process: pH, temperature, enzyme, meal, and oxygen concentrations. It was found that: (1) the natural buffering capacity of CM resulted in a negligible effect of the pH of the buffer, which was used as the continuous phase in the process, on the extent of decrease in sinapic acid esters (SAE); (2) the system was saturated with the enzyme when its concentration was 4 nkat/mL of the continuous phase; and (3) the optimum temperature was 50 degrees C. The process could be carried out even at higher temperatures due to the protective action of CM, which resulted in an increase in the thermal stability of the enzyme. The particle size influenced the extraction of the SAE from the meal, indicating that, at lower SAE concentrations, the process became diffusion limited. This result, together with those showing no effect of the intensity of agitation, indicated that the enzymatic process can be characterized by high Biot numbers. During the enzymatic process, the molar concentration of available oxygen can become a limiting factor when it is more than four times lower than the molar concentration of phenolics in the treated meal. The new enzymatic method was compared with other methods reported in the literature for the decrease in the phenolic content of rapeseed meals. It was found that, among the methods tested, the enzymatic treatment was the most effective, followed by the lime treatment. The enzymatic process did not reduce the quality of the protein isolates prepared from the CM. After the addition of a simple acetone-washing step, the isolate from the enzymatically treated meal had even better properties. Copyright 1999 John Wiley & Sons, Inc.

Journal Article↗

PubMed1998

Transformation of 3,5-dimethoxy,4-hydroxy cinnamic acid by polyphenol oxidase from the fungus Trametes versicolor: product elucidation studies.

Sinapic acid (SA), 3,5-dimethoxy,4-hydroxy cinnamic acid, was incubated with a crude polyphenol oxidase from the fungus Trametes versicolor. Some products of this transformation were isolated and their structures identified using mass spectrometry, nuclear magnetic resonance and Fourier transform infrared spectroscopy, and X-ray crystallography. It was found that the enzymatic oxidation of SA includes two distinct phases. In the initial phase SA is enzymatically transformed to r-1H-2c,6c-bis-(4'-hydroxy-3', 5'-dimethoxyphenyl)-3,7-dioxabicyclo-[3,3,0]-octane-4,8-dione, dehydrodisinapic acid dilactone. The mechanism of this reaction may involve coupling of two phenoxy radicals by the beta-beta mode and subsequent intramolecular nucleophilic attack. In the second phase dehydrodisinapic acid dilactone is transformed by polyphenol oxidase into several intermediate products, including 4-(4-(3, 5-dimethoxy-4-oxo-2,5-cyclohexadienyliden)-1, 4-dihydroxy-(E)-2-butenylidene)-2,6-dimethoxy-2, 5-cyclohexadien-1-one. The final product of the overall transformation of SA is 2,6-dimethoxy-p-benzoquinone. The obtained results were used to propose a part of the transformation pathway for the enzymatic oxidation of SA by polyphenol oxidase.

Basidiomycota↗

PubMed1996

Comparison of 3 methods for the determination of sinapic acid ester content in enzymatically treated canola meals.

The enzymatic reduction of sinapic acid ester content in canola meal using polyphenol oxidase from the fungus T. versicolor was investigated. To determine the effectiveness of this new process, the results obtained using two spectrophotometric methods and an HPLC analytical method for assaying sinapic acid ester content in the treated and untreated meals were compared. It was found that all the methods gave practically the same results when the samples from untreated canola meals were analysed. However, both of the spectrophotometric methods overestimated the sinapic acid ester content in the enzymatically treated meal by 7%-20%, as compared to the results obtained using HPLC. It was found that the sensitivity limits for the spectrophotometric methods used for the determination of sinapic acid ester content in enzymatically treated canola meals were 2.67 g and 1.47 g phenolics/kg meal for the direct and chemical spectrophotometric methods respectively. A correlation between the results obtained using the spectrophotometric and HPLC methods is given. The enzymatic treatment resulted in a negligible amount of phenolics in the treated meal.

Artifacts↗