Tania A. Anazawa

Biodegradation of polycyclic aromatic hydrocarbons by soil fungi

Thirteen deuteromycete ligninolytic fungal strains were grown in media containing polycyclic aromatic hydrocarbons (PAHs), for 6 and 10 days. The PAHs were added directly with the inocula or on the third day of cultivation. A selection of the best strains was carried out based on the levels of degradation of the PAHs and also on the ligninolytic activities produced by the fungi. The selected strains were cultivated for 3, 6, 9, 12 and 15 days in the PAHs-containing media. Degradation of PAHs, as measured by reversed-phase HPLC on a C18 column, varied with each strain as did the ligninolytic enzymes present in the culture supernatants. Highest degradation of naphthalene (69%) was produced by the strain 984, having Mn-peroxidase activity, followed by strain 870 (17%) showing lignin peroxidase and laccase activities. The greatest degradation of phenanthrene (12%) was observed with strain 870 containing Mn-peroxidase and laccase activities. When anthracene was used, the strain 710 produced a good level of degradation (65%).

Radiation immobilization of poly(methyloctylsiloxane) on silica for use in HPLC: a uniform layer model.

Poly(methyloctylsiloxane) (PMOS) was sorbed into the pores of HPLC silica by a solvent evaporation procedure, then irradiated with gamma rays from a cobalt-60 source to absorbed doses in the range from 0 to 200 kGy (1Gy = 1J kg-1). Non-irradiated and irradiated samples were characterized by solvent extraction, specific surface area determination, infrared spectroscopy and reversed-phase column performance. Solvent extraction data reveal that about 40% of the PMOS is not extractable prior to irradiation and this increases to about 75% with radiation doses of 50 kGy or higher. Column performance was improved by the radiation treatment, reaching a maximum efficiency in the dose range of 80-140 kGy while the peak symmetry changed from As = 1.7 to 1.1. The improvement is attributed to the increased mass of polymer immobilized by the radiation treatment and to a more uniform distribution of the immobilized polymer in the silica pore system. A multi-layer stationary-phase model is presented in which the first layer consists of an adsorbed monolayer of PMOS and the second layer is immobilized by gamma radiation.

Polymethyloctilsiloxane Adsorbed on Porous Silica as a Packing Material for Reversed Phase High Performance Liquid Chromatography

Abstract Packing material having 10, 20, 30, 40 and 50% loadings of polymethyloctilsiloxane on porous silica particles have been prepared and tested. Solvent extraction tests, measurements of physical properties and determinations of chromatographic parameters show that an initial loading of 40% gives a packing material with satisfactory chromatographic properties.

The Chromatographic Behavior of Coated Stationary Phases with Different Silicas

Abstract ABSTRACT Different silicas coated with poly(methyloctylsiloxane) are compared in terms of the effect of particle shape, particle diameter, mean pore diameter and specific surface area. For irregular particles, the carbon contents (% C) coated are essentially identical even though there are considerable variations in surface area for the different silica supports. Sample retentions (k) increase with increasing surface area while efficiences (N/m, naphthalene) increase as the particle diameter decreases. Excellent peak symmetries (As) are obtained with most packings. Spherical particles, with significantly lower surface areas, have lower carbon loadings and higher surface coverage but produce columns with significantly higher efficiences than the irregular particles having similar particle diameter.

The spatial distribution of poly(methyloctylsiloxane) deposited by solvent evaporation in the pores of HPLC silica particles

SummaryPoly(methyloctylsiloxane) (PMOS), sorbed into the pores of HPLC silica particles by solvent evaporation, can function as a useful stationary phase for reversed-phase chromatography. The present work addresses the question of how the PMOS is distributed in the pores. Measurements of the surface area (BET, N2) of a series of partially loaded samples (0–40% PMOS, m/m) using a typical batch of HPLC silica (10 μm irregular particles with 6 nm pores) show that the specific surface area of the samples decreases linearly with the specific loading (mass of PMOS per gram of silica). This result is not consistent with a “film” model in which the PMOS is deposited uniformly on the pore walls, but is consistent with a model in which long segmented “plugs” of PMOS are deposited within the pore system.

Stability of high-performance liquid chromatography columns packed with C1 and C8 polysiloxanes sorbed into porous silica particles

Abstract Columns, packed with 10 μm diameter porous silica particles (15 nm diameter pores) containing polydimethylsiloxane (20%, w/w) or polymethyloctylsiloxane (40%, w/w) sorbed into the pores, were tested for chromatographic stability as a function of elution volume. No significant changes in efficiency, retention factor or separation factor were observed following extended washing (up to 5000 column volumes) of either stationary phase with methanol-water mobile phases.

Enzymes produced by soil fungi following microaerobic growth on lignocellulosic materials

Four fungal strains able to grow under low oxygenation conditions were selected and used in studies to determine the production of enzymes (endoglucanases, exoglucases, β-glucosidase, and peroxidases) that promote the degradation of lignocellulosic materials. The capacity of the fungi to ferment lignocellulosic materials was also investigated. Avicel, xylan, Whatman no. 1 filter paper, or agroindustrial residues were used as carbon sources in a medium containing mineral salts, vitamins, and cysteine as a reducing agent, under either microaerophilic or combined conditions (aerobic followed by microaerophilic conditions). The results obtained with strains Q10, H2, and LH5 suggest that they prefer a low oxygen concentration for growth and enzyme production. However, strain F20 seems to need higher levels of oxygenation. Lignocellulolytic activities were detected in all strains but varied with the carbon source used for growth. In general, the highest levels of these activities were produced by strain H2 under microaerophilic conditions. Ethanol and other nongaseous fermentation products were detected following high-performance liquid chromatography analysis using a Supelcogel C-610H column, demonstrating the fermentative capability of these strains.

Chromatographic comparison of self-immobilized and radiation-immobilized poly(methyloctylsiloxane) stationary phases on various silicas

Self-immobilized and radiation-immobilized stationary phases were prepared with poly(methyloctylsiloxane) on eight silica supports having different particle sizes, particle shapes and pore sizes. Columns prepared by the two immobilization procedures had similar efficiencies, resolutions and separation factors but columns with self-immobilized stationary phases had lower percent loadings and, thus, lower retention factors. Results show structural differences between the phases.