Controle da formação de biofilme por bactérias Presentes em fluidos de corte utilizando biocida e óleos essenciais

Abstract

Cutting fluid is any kind of fluid used for cutting or machining materials, being also an emulsion formed by oil and water. Machining without cutting fluid presents a high cutting force and high levels of roughness, so the use of cutting fluids is required for cooling, lubrication and cleaning of the part. This emulsion is susceptible to the growth of microorganismscapable of forming biofilm, which may contaminate the fluid and cause damage resulting from chemical compounds excreted by the bacteria.Thus, the objective was to verify biofilm formation capacity by bacteria present in cutting fluids as much as the efficiency of synthetic and natural biocides to inhibit biofilm formation. For this, samples were taken on a milling machine at the Federal University of Technology - Paraná (UTFPR) – CornélioProcópio Campus and inoculated in Petri dishes with Plate Count Agar (PCA) solid growth medium. The isolation of the colonies, morphological characterization and Gram’s staining and biofilm formation test for isolated and associated bacteria were performed.The biofilm formation occurred by reading the optical density at 450nm in an ELISA system and it enabled the bacteria and associations to be classified as non-forming, weak, moderate or strong forming. In the second stage of the test, synthetic biocide or essential oils in 1% concentration were added and the effectiveness of inhibitors in reducing the formation of biofilms was identified. In larger quantities, the growth of Gram-positive bacteria, 65% in vegetable fluid and 55% in mineral, and in the shape and arrangement of staphylococci (40% in vegetable fluid and 22% in mineral) and bacilli (41% in vegetable fluid and 35% in mineral) was noted. There was biofilm formation regardless of the used cutting fluid origin, but when considered the normal biofilm growth, without the addition of inhibitors, the mineral fluid was more susceptible to the presence of moderate biofilm forming bacteria.There was no significant difference between individual bacteria or associations both in biofilm formation as in its inhibition for both fluids.In the mineral fluid, the result of the synthetic biocide was similar to the clove essential oil for inhibiting biofilm formation and they were the most effective in this role, 100% non-biofilm-forming. In the vegetable fluid, the synthetic biocide was the most efficient for reducing biofilm formation, 83% non-forming and 17% weak forming for single and pairs and 100% non-forming in trios. The essential oils have only showed efficiency in reducing the biofilm in the vegetable fluid for trios associations. For the reduction of biofilm formation, the synthetic biocide was more efficient in both fluids, although the use of essential oils is preferred since it is removed from a natural/renewable source.