A facile, highly regio- and enantioselective amino-thiocarbamate-catalyzed bromolactonization of cis-1,2-disubstituted olefinic acids has been developed. The use of the enantio-enriched lactones in the synthesis of chiral synthetic intermediates is also demonstrated.
Five commercially available assay kits were tested on the same protein sample with the addition of 17 different types of interfering substances typically found in the biological wastewater treatment, and a comparison of the use of these assays with 22 different protein and peptide samples is also presented. It was shown that a wide variety of substances can interfere dramatically with these assays; the metachromatic response was also clearly influenced by different proteinaceous material. Measurement of the "protein" content in the effluent of an anaerobic membrane bioreactor was then carried out using these assay methods. Quantitative results of the "protein" concentration in the different effluent samples, with or without spiked additions of Bovine Serum Albumin (BSA), showed considerable disagreement. We concluded that the "protein" measured in wastewater samples using standard colorimetric assays often shows false positive results and has little correlation to their real value. A new analytical method needs to be developed in order to gain greater insight into the biological transformations occurring in anaerobic digestion, and how soluble microbial products (SMPs) are produced.
Effluents from wastewater treatment systems contain a variety of organic compounds, including end products from the degradation of influent substrates, nonbiodegradable feed compounds, and soluble microbial products (SMPs) produced by microbial metabolism. It is important to identify the major components of these SMPs to understand what is in wastewater effluents. In this study, physical pretreatments to extract and concentrate low molecular weight SMPs (MW< 580 Da) from effluents were optimized. Liquid-liquid extraction (LLE) of a 200 mL effluent sample showed the best performance using a mixture of n-hexane, chloroform, and dichloromethane (70 mL) for extraction. For solid phase extraction (SPE), two OasisHLB cartridges were connected in-line to optimize recovery, and the eluted samples from each cartridge were analyzed separately to avoid overlapping peaks. Four solvents varying from polar to nonpolar (methanol, acetone, dichloromethane, and n-hexane) were selected to maximize the number of compound peaks eluted. A combination of SPE (OasisHLB) followed by LLE was shown to maximize compound identification and quantification. However, the compounds identified accounted for only 2.1 mg of chemical oxygen demand (COD)/L (16% of total SMP as COD) because many SMPs have considerably higher MWs. Finally, the method was validated by analyzing a variety of different reactor effluents and feeds.
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