The broad possibilities of electrochemical impedance spectroscopy for assessing the capacitance of interphase boundaries; the resistance and thickness of the foulant layer were shown by the example of AMX-Sb membrane contacted with red wine from one side and 0.02 M sodium chloride solution from the other side. This enabled us to determine to what extent foulants affect the electrical resistance of ion-exchange membranes, the ohmic resistance and the thickness of diffusion layers, the intensity of water splitting, and the electroconvection in under- and over-limiting current modes. It was established that short-term (10 h) contact of the AMX-Sb membrane with wine reduces the water-splitting due to the screening of fixed groups on the membrane surface by wine components. On the contrary, biofouling, which develops upon a longer membrane operation, enhances water splitting, due to the formation of a bipolar structure on the AMX-Sb surface. This bipolar structure is composed of a positively charged surface of anion-exchange membrane and negatively charged outer membranes of microorganisms. Using optical microscopy and microbiological analysis, it was found that more intense biofouling is observed on the AMX-Sb surface, that has not been in contacted with wine.
A method for purification of enzymes from the ligninolityc complex of the basidiomycete Trametes pubescens (Schumach.) Pilat has been elaborated. Two homogeneous isoforms of laccases (laccase 1 and laccase 2) as well as a homogeneous preparation of lignin peroxidase were isolated. Basic biochemical parameters of the enzymes were determined, such as the molecular weights (67, 67, and 45 kD, respectively), isoelectric points (5.3, 5.1, and 4.2, respectively), as well as content and composition of the carbohydrate moiety of the laccases (N-acetylglucosamine, mannose, and xylose). The pH dependences and thermal stabilities of the laccases were investigated. The kinetic parameters of the enzymatic reactions catalyzed by the laccases were determined using different substrates, such as catechol, hydroquinone, 2,2 -azinobis-(3-ethylbenzthiazoline-6-sulfonate), and K4Fe(CN)6. The structure of the active sites of both laccases and the lignin peroxidase were studied by EPR, CD, and UV-VIS spectroscopy, as well as using fluorescence analysis. Our studies showed similarity of the spectral characteristics of the two laccases, whereas their kinetic properties were found to be different.
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