Microbioma do fluido de corte utilizado na indústria metal-mecânica brasileira: composições quantitativa e qualitativa, fatores que influenciam a presença de microrganismos, biodegradação e impacto nas propriedades lubri-refrigerante

Abstract

Introduction: Cutting fluids (CF) are complex mixtures of chemicals used in the metalworking industry for cooling and lubricating of different types of machining processes, and their performance can directly affect the productivity of these processes. Objectives: i.) determine the dominant biome in miscible cutting fluids in water; ii.) analyze quantitatively and qualitatively this biome, including for the presence of M. immunogenum; iii.) determining the physic-chemical parameters such as pH, and others such as temperature and concentration of the fluid during biodegradation; iv.) evaluate the influence of biocides in the contamination of CFs; v.) determine the lubrication and cooling performance of two CFs after artificial contamination "in vitro" in two moments of biodegradation: when it reaches 105 CFU / mL (lag growth phase) and after 70 days of artificial biodegradation "in vitro" (last growth phase ), compared with new cutting fluids / uncontaminated and dry environment; and, vi.) to evaluate aspects of fluid management, as the use of prevention practices of accidents / health of employees, of injuries resulting in absenteeism and hygiene and cleanliness. Methods: In total, 114 samples were analyzed microbiologically of FCs three metal-mechanical industries located in the Brazilian Southeast (2) and South (1), all non-automotive. The microbial monitoring of bacteria and fungi was performed by viable count by specific means. The investigation of microbial contamination and degradation of CFs containing (7) or not biocide (2) was performed by monitoring, random (three industries) and continuous (two industries). Additionally, in one industry two CFs were selected for a study artificial contamination "in vitro" for a period of 70 days using as the most prevalent microorganism’s inoculum when the ongoing monitoring this industry. The test pendulum rebound hammer was used to evaluate the influence of microbial contamination in the performance of the properties of FCs as well as possible effects on the quality of the machined parts. Information and documents relating hygiene practices and cleaning industries, as well as health and absenteeism grievances were collected. Results: there was a high microbiological contamination in CFs analyzed, usually above 106 CFU / mL, regardless of the investigated industry with a common microbial biome consisting of Gram-negative bacilli (75.0%), with the prevalence of bacteria oxidative metabolism (55.0%) with Pseudomonas sp. as main representative, associated with low risk of the disease "lung machine operator". In most situations evaluated when the random monitoring the presence of high densities of microorganisms in CFs was not affected by the presence of biocides, but most CFs containing biocide (77.7%), bioconcept (11.1%), bioconcept + biocide (11.1%) and only one without this condom (11.1%), showing mean counts of viable, respectively, 3.7 x 107 CFU / mL 2.0 x 105 CFU / mL, 3.6 x 107 CFU / mL and 5.8 x107 CFU / mL. Similar results were also observed when the continuous monitoring of fluids, except for the mineral base containing biocide, with no contamination by 16 months of observation. The lubrication and cooling performance of two CFs, a mineral-based and vegetable-based, was determined by the energy consumed during scratching, in two moments of artificial biodegradation "in vitro" of these CF, after reaching 105 CFU / mL and 70 days, being significantly higher (P <0.05) in the second evaluation (70 days) compared when using new / non-contaminated FC. Hygiene practices and cleanliness of the workplace were less than ideal, with apparent dirt, and varied in the three industries, observing a lack of written documents on relevant aspects to hygiene and cleanliness. On the other hand, managers reported no occurrence of occupational disease and insignificance in absenteeism of employees. Conclusions: measures are needed such as: the use of CFs more effective biocides, which are subject to routine microbiological monitoring for early response when the contamination in an industry with good manufacturing practices, which are necessary to avoid contamination, multiplication and biofilm formation, and ensure a productive machining.