Adsorption and Biodegradation of Aromatic Chemicals by Bacteria Encapsulated in a Hydrophobic Silica Gel

An adsorbent silica biogel material was developed via silica gel encapsulation of <i>Pseudomonas</i> sp. NCIB 9816-4, a bacterium that degrades a broad spectrum of aromatic pollutants. The adsorbent matrix was synthesized using silica precursors methyltrimethoxysilane and tetramethoxysilane to maximize the adsorption capacity of the matrix while maintaining a highly networked and porous microstructure. The encapsulated bacteria enhanced the removal rate and capacity of the matrix for an aromatic chemical mixture. Repeated use of the material over four cycles was conducted to demonstrate that the removal capacity could be maintained with combined adsorption and biodegradation. The silica biogel can thus be used extensively without the need for disposal, as a result of continuous biodegradation by the encapsulated bacteria. However, an inverse trend was observed with the ratio of biodegradation to adsorption as a function of log <i>K</i>_ow, suggesting increasing mass-transport limitation for the most hydrophobic chemicals used (log <i>K</i>_ow > 4)

Quantification of intracellular trehalose in wild-type CHO cells and CHO-TRET1 cells.

<p>Cells were incubated in fully complemented cell culture medium containing 400 mM trehalose for 4 hours (<i>n</i> = 3, ± SD).</p

Glass transition temperature of the dried spinning solution (1.8 M trehalose, 10 mM KCl, 5 mM glucose, 20 mM HEPES, 120 mM choline chloride, pH 7.4) using FTIR technique.

<p>The figure indicates a characteristic peak-position of ν-OH stretch plotted against decreasing temperature.</p

Survival of CHO-TRET1 cells spin-dried in solutions with or without trehalose, then stored in LN₂ for 1 h, and finally rehydrated.

<p>(A) Membrane integrity of spin-dried cells stored in LN₂ for 1 h and 45 min after thawing and rehydration (B) Micrograph of the spin-dried cells after thawing and rehydration. (C) Growth of spin-dried cells after thawing and rehydration. The values were normalized to the initial cell count (<i>n</i> = 10, ± SD).</p

Survival of CHO-TRET1 cells spin-dried in buffers with or without trehalose and rehydrated immediately following desiccation.

<p>(A) Membrane integrity of spin-dried cells 45 min after rehydration (B) Micrograph of the cell samples after spin drying and rehydration. (C) Growth of cells after spin-drying and rehydration. The values were normalized to the initial cell count (<i>n</i> = 10, ± SD).</p

FTIR analysis of the dried film obtained after spin drying of sample buffer (1.8 M trehalose, 10 mM KCl, 5 mM glucose, 20 mM HEPES, 120 mM choline chloride, pH 7.4).

<p>The ratio of I₁₆₅₀/I₁₁₅₀ was used to quantify local water contents.</p

Basic configuration of the spin-drying apparatus.

<p>The cells were grown on glass cover slips prior to the spin-drying. During spin-drying, the glass cover slip was held in place by a vacuum chuck.</p

<i>In Silico</i> Identification of Bioremediation Potential: Carbamazepine and Other Recalcitrant Personal Care Products

Emerging contaminants are principally personal care products not readily removed by conventional wastewater treatment and, with an increasing reliance on water recycling, become disseminated in drinking water supplies. Carbamazepine, a widely used neuroactive pharmaceutical, increasingly escapes wastewater treatment and is found in potable water. In this study, a mechanism is proposed by which carbamazepine resists biodegradation, and a previously unknown microbial biodegradation was predicted computationally. The prediction identified biphenyl dioxygenase from <i>Paraburkholderia xenovorans</i> LB400 as the best candidate enzyme for metabolizing carbamazepine. The rate of degradation described here is 40 times greater than the best reported rates. The metabolites <i>cis</i>-10,11-dihydroxy-10,11-dihydrocarbamazepine and <i>cis</i>-2,3-dihydroxy-2,3-dihydrocarbamazepine were demonstrated with the native organism and a recombinant host. The metabolites are considered nonharmful and mitigate the generation of carcinogenic acridine products known to form when advanced oxidation methods are used in water treatment. Other recalcitrant personal care products were subjected to prediction by the Pathway Prediction System and tested experimentally with <i>P</i>. <i>xenovorans</i> LB400. It was shown to biodegrade structurally diverse compounds. Predictions indicated hydrolase or oxygenase enzymes catalyzed the initial reactions. This study highlights the potential for using the growing body of enzyme–structural and genomic information with computational methods to rapidly identify enzymes and microorganisms that biodegrade emerging contaminants