High enrichment of MMP-9 and carboxypeptidase A by tweezing adsorptive bubble separation (TABS).

Tweezing adsorptive bubble separation (TABS) was used as a method for the enrichment of matrix metalloproteinases (92-kDa type IV, gelatinase B (MMP-9)) and carboxypeptidase A (CPA) from dilute aqueous solutions. The method is based on the chelation of metalloenzymes applying 2-(carbamoylmethyl-(carboxymethyl)amino)acetic acid (ADA) coupled with an octyl part to form a surface active unit. MMP-9 could be enriched with an enrichment ratio of 12.0 and a recovery of 87.3%, and CPA could be enriched 18.8-fold and with 95.3% recovery. Both enzymes were enriched without significant losses of enzymatic activity. To verify that the enzymes were tweezed by ADA-C8 without abstraction of the zinc ions from the active center, TABS trials were additionally conducted with zinc ions in complex with ADA-C8, which revealed only negligible enrichment ratios of the enzymes (2.2 for MMP-9 and 0.2 for CPA). The results obtained impressively demonstrate that zinc-containing proteases can be enriched selectively and efficiently by TABS.

Permissible level of toxaphene residues in fish from the German market based on in vivo and in vitro effects to tumor promotion.

Toxaphene is a chlorinated pesticide consisting of more than 200 congeners that are mainly chlorobornanes and chlorocamphenes. As the congeners exhibit different stability properties in the environment, only between 20 and 30 compounds can be observed in, e.g., fish, which are represented by technical toxaphene as a mixture. In human body, the congeners Parlar #26, #40, #41, #44, #50, and #62 are detected frequently. Three of them, #26, #50, and #62, pose a potential risk to human health due to their persistent characteristic. By using experimental results of a European Union study (MATT, 2000. Investigation into the Monitoring, Analysis and Toxicity of Toxaphene in Marine Foodstuffs, European Union, Brussels, Final report, FAIR CT PL.96.3131. Investigation into the Monitoring, Analysis and Toxicity of Toxaphene in Marine Foodstuffs), a reference dose related to tumor promotion was calculated for these representative persistent toxaphene congeners. In Germany, the sum of the congeners #26, #50, and #62 is defined as the official standard for toxaphene residues in food. In this work, different fish samples obtained from German markets were studied regarding their contamination with toxaphene congeners, presented either in sum, or as single constitutes. The obtained data were used to define the acceptable total concentration of the sum of Parlar #26, #50, and #62 with regard to prevention of tumor promotion in human. The results showed that the currently existing permissible level of the sum of these congeners (0.1 mg/kg) is higher than the acceptable concentration in fish samples determined by this work and calculated at ca. 0.090 mg/kg. It is therefore recommended to improve the permissible level of toxaphene in German food samples.

Efficiency of foam fractionation for the enrichment of nonpolar compounds from aqueous extracts of plant materials.

Biologically active compounds from several useful plants were enriched using foam fractionation, a separatory method belonging to the adsorptive bubble separation (ABS). Nonpolar humulones (1-6) from Pilsener beer, curcuminoids (7-9) from turmeric, and carotenoids (16 and 17) from carrot juice were enriched fast and quantitatively, depending on the process parameters, whereas more polar compounds such as catechins from green tea (11, 12, 14, and 15) and naringin (18) and hesperidin (19) from orange and grapefruit juices could not be enriched.

High efficiency enrichment of total and single whey proteins by pH controlled foam fractionation.

The feasibility of foam fractionation, as an alternative to other more commonly used methods, to effectively separate total whey proteins and single fractions has been studied. The investigation focused on the effects of different process parameters such as the pH value, the initial protein concentration, the flow rate and the addition of sodium dodecyl sulfate concentration as a surfactant. Whey proteins could be almost completely enriched into the foam fraction at pH values between 2 and 3; only traces of them remained in the residual whey solution. Albumin bovine, beta-lactoglobulin and alpha-lactalbumin from whey solutions in the presence of sodium dodecyl sulfate could be transferred into the foam fraction with enrichment ratios of up to 30 and with recovery rates between 64.5% and 99.8%. The results demonstrate that enriching whey proteins using foam fractionation can be quantitative and effective according to process parameters.

Enrichment of the glycoalkaloids alpha-solanine and alpha-chaconine from potato juice by adsorptive bubble separation using a pH gradient.

For the first time, the solanidine alkaloids alpha-solanine and alpha-chaconine could be quantitatively enriched from potato juice by Adsorptive Bubble Separation (ABS) with a pH gradient. The enrichment into the foam was influenced by the pH value, bubble size, and gas flow rate. The efficiency was highest on using diluted samples with a concentration between 2 and 6 mg L(-1) of the alkaloids at pH 6.0. The experiments with a standard solution of each alkaloid confirmed that these substances can be quantitatively enriched into the 'spumat' without surface active potato proteins. The transfer into the foam fraction under these conditions was similar to that from the aqueous potato extract.

Quantitative elimination of Flavokavines A and B from Kava Kava (Piper methysticum G. Forst) by isoelectric focused adsorptive bubble separation.

Adsorptive bubble separation, though still rarely used, is a suitable method for enrichment of surface-active macromolecules such as enzymes and proteins. There is a lack of investigations with small molecules, which can also be separated from complex mixtures by this method. In this work, an aqueous extract of Kava Kava ( Piper methysticum G. Forst) was used as a model system. Enrichment of undesirable Flavokavine A (7) and Flavokavine B (8) in the foam was influenced by the pH value, the amount of saponin as surface active substance, and the flow rate of the foam-forming gas. Efficiency was highest with diluted samples at pH 6.5. Under these conditions, transfer of Kavapyrone (1-6) to the foam was negligible.