Desenvolvimento de métodos para estudo de dioxinas presentes na cinza do bagaço da cana-de-açúcar : avaliação do potencial biorremediador de cepas microbianas em compostagem aeróbica

Abstract

Sugarcane bagasse ash is a byproduct of sugar and alcohol industry with potential for field application. However, the presence of organic contaminants such as dioxins turns necessary the development of strategies for removal of those pollutants, such as bioremediation. Because of the high toxicity of dioxins, it is wise to develop effective and low risk methods for initial evaluation of microbial degradation capacity of those compounds by using less dangerous alternatives such as screening tools to select possible microorganisms as candidates for bioremediation. In such context, this work aimed to apply statistical models to evaluate microbial growth capacity under influence of components of a compost windrow already used for other sugarcane industry residues, and also development of qualitative and quantitative methods to evaluate microbial degradation of the dye RBBR and 1,2,3,4-TCDD, molecules selected as model compounds. The Scott-Knott method grouping multiple means showed good results, indicating microbial growth inhibition of all fungi in culture medium with compost windrow, and microbial growth promotion for Aspergillus strains in sugarcane ash doped medium. Furthermore, quantification of RBBR dye in liquid broth was developed, validated and applied through a dilute-and-shoot technique followed by LC-MS/MS, where it was possible to detect up to 4,8pM of dye, being observed a degradation from 40-99% of dye over 30 days. In a similar way, it was developed and validated a GC-MS method to quantify 1,2,3,4-TCDD in liquid broth after extraction, with detection limits of 10ppb, observing a removal of up to 20% of dioxin after 30 days. Another point evaluated was the identification of RBBR degradation products, where it was observed the presence of four dye metabolites during the course of the experiment, which allowed us to propose a degradation pathway of RBBR dye by Aspergillus flavus.