Experimental Results and Integrated Modeling of Bacterial Growth on an Insoluble Hydrophobic Substrate (Phenanthrene)

Metabolism of a low-solubility substrate is limited by dissolution and availability and can hardly be determined. We developed a numerical model for simultaneously calculating dissolution kinetics of such substrates and their metabolism and microbial growth (Monod kinetics with decay) and tested it with three aerobic phenanthrene (PHE) degraders: Novosphingobium pentaromativorans US6-1, Sphingomonas sp. EPA505, and Sphingobium yanoikuyae B1. PHE was present as microcrystals, providing non-limiting conditions for growth. Total PHE and protein concentration were tracked over 6-12 days. The model was fitted to the test results for the rates of dissolution, metabolism, and growth. The strains showed similar efficiency, with v(max) values of 12-18 g dw g(-1) d(-1), yields of 0.21 g g(-1), maximum growth rates of 2.5-3.8 d(-1), and decay rates of 0.04-0.05 d(-1). Sensitivity analysis with the model shows that (i) retention in crystals or NAPLs or by sequestration competes with biodegradation, (ii) bacterial growth conditions (dissolution flux and resulting chemical activity of substrate) are more relevant for the final state of the system than the initial biomass, and (iii) the desorption flux regulates the turnover in the presence of solid-state, sequestered (aged), or NAPL substrate sources

Estudio del ciclododecano como barrera temporal en el moldeado de esculturas pétreas y piezas ornamentales

This paper describes the study of the hydrocarbon cyclododecane (C12H24) and its suitability as a temporary barrier in the moulding of petrous pieces of different porosities. For this purpose, two types of petrous materials were chosen, Bateig biocalcarenite from Novelda (Alicante, Spain) and marble from Estremoz (Evora, Portugal). The moulding process of a work of art is a very complex task entailing an exhaustive study of the piece and the selection of the most ideal barrier to prevent the presence of residues and unwanted chromatic changes over time. Therefore, the intervention methodology was based on both the preparation of petrous specimens with different dilutions of CDD and subsequent testing samples to study their accelerated ageing by irradiation with ultraviolet light. The results were obtained with colorimetric measurements and Fourier transform infrared spectroscopy (FT-IR). When using CDD as a temporary barrier on different types of stone, we observed some very important properties in relation to other more generally used mould-release agents; its sublimation capacity prevents the presence of residues and chromatic changes, thus making it one of the most promising substances in the field of Conservation and Restoration of Cultural Property.En esta comunicación se describe el estudio del hidrocarburo cyclododecane (C12H24) y su idoneidad como temporary barrier en el moldeado de piezas pétreas con diferente porosidad. Para ello, se han elegido dos tipos de materiales pétreos, la biocalcarenite Bateig de Novelda (Alicante, España) y el mármol de Estremoz (Évora, Portugal). El proceso de moldeado de una obra de arte es una tarea muy compleja que requiere de un estudio exhaustivo de la pieza y de la elección del barrier más idóneo que impida, con el tiempo, la presencia de residuos y cambios cromáticos indeseables. En este caso, la metodología de actuación se basó en preparar probetas de ambos materiales pétreos con diversas disoluciones de CDD y someterlas a ensayos de envejecimiento acelerado por irradiación con luz ultravioleta. Los resultados se obtuvieron a través de medidas de colorimetría y espectroscopía infrarroja por transformada de Fourier (FT-IR). Se observó que el CDD, empleado como temporary barrier en piedras de diversa naturaleza, presenta unas propiedades muy destacables con respecto a otros desmoldeantes de uso más generalizado y, la capacidad de sublimación que posee impide la presencia de cualquier residuo y cambio cromático, convirtiéndolo en una de las sustancias más prometedoras en el campo de la Conservación y Restauración de Bienes Culturales.Mas Barberà, X.; Van Uden, A.; Kröner, SU.; Martínez Bazán, ML. (2008). The study of cyclododecane as a temporary barrier in the molding of stone sculptures and ornaments. Arché. (3):179-184. http://hdl.handle.net/10251/31807179184