Resumo

GOMEZ DE SARAVIA, S. G.  e  FERNANDEZ LORENZO DE MELE, M.. Non-invasive methods for monitoring biofilm growth in industrial water systems. Lat. Am. appl. res. [online]. 2003, vol.33, n.3, pp.353-359. ISSN 0327-0793.

Microbiological control in industrial environments is frequently restricted to monitor the number of planktonic (suspended) cells. However, this number is not often related with the microorganisms attached to the surfaces (sessile bacteria). The aim of this research work was to develop a method for monitoring biofilm growth and the biocidal efficacy through simple non-invasive ways. With this purpose, biofilms were formed on stainless steel coupons and after preset periods were removed and immersed in sterile solutions with and without biocide. The number of sessile cells attached on the metal surface and of planktonic cells that were shed from the biofilmed coupons (pcb) and grow in the initially sterile solutions were determined. Sessile cells were scrapped from the metal surface to be enumerated. The relation between the degree of growth of pcb and the reactivation capacity of the biofilm was evaluated. It could be observed that pcb growing in a nutrient non aggressive medium was related to the number of sessile cells that remain alive after the biocidal treatment. The early stages of the biofilm growth, the thickness of the biofilms and their microstructural characteristics before and after the biocidal treatment could be followed through optical microscopy using a non-invasive technique recently developed in the laboratory. Microscopic observations showed that the biofilm thickness varied to obliterate the unevenness of rough surfaces.

Palavras-chave : Biofilm; Biocide; Biocidal Treatment; Optical Microscopy; Pseudomonas Fluorescens.

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