Avaliação da biodegradação da solução residual da coloração de Gram por basidiomicetos

Abstract

Dyes and their residues cause numerous environmental problems when they are improperly disposed of in the environment. This study evaluated the biodegradation of a residual solution of Gram staining (SRCG) with different basidiomycete species. This staining technique is used in the characterization of bacteria in Microbiology laboratories. The research was divided into four stages. In the first one, it was tried to evaluate if the addition of nutrients in the media of culture with dyes would favor or not the biodegradation. For this, nine basidiomycetes were cultured in Petri dishes in media containing 6.25% of SRCG, solidified with agar or potato dextrose agar. It was observed that the concentration of the dye did not significantly inhibit the microbial growth and that the nutrient supplementation favored the discoloration of the medium. In the second assay the effect of increasing the concentration of the dye on the fungal growth was evaluated, exposing the basidiomycetes to 6.25%, 12.5%, 25% and 50% of SRCG. It was observed that with 50% and 25% of the concentration the inhibition occurred the microbial growth, indicating the toxicity of the solution. In this study the Pleurotus ostreatus fungus was chosen for studies in liquid medium, based on the statistical analysis of the data. The third study was carried out through a complete factorial design 23. The factors studied were: static or agitated cultivation, addition or absence of rice husk, addition of glucose at concentrations of 10 and 20 g / L. By following the UV-Vis discolouration and the phenolic concentration by the Folin-Ciocalteau method, it was observed that the best condition was 20 g / L glucose, without agitation and without addition of rice husk, resulting in discoloration of 96.5% and removal of phenols 97.8%. Kinetic analysis of biodegradation indicated that up to the third day of the experiment with P. ostreatus there was intense microbial activity, with glucose consumption and simultaneous removal of color (67%) and phenolic compounds from 1456.3 mg GAE / g for 8.7 mg GAE / g. However, it has been observed that the discoloration of the medium may have occurred under strong influence of dye adsorption processes on the fungal mycelium.