Decoloration of dye from the efluents of the textile industry by macromicetos

Abstract

El tratamiento de los efluentes provenientes de la industria textil constituye un importante desafío tecnológico. La descoloración de dichas aguas residuales mediante métodos químicos, físicos y biológicos tradicionales presenta como principales desventajas los elevados costos, bajas eficiencias y aplicabilidad limitada. Por estas razones, el propósito de esta tesis es proporcionar, desde un enfoque interdisciplinar, soluciones innovadoras para la resolución de dichos problemas. Asimismo, también se plantea en esta tesis la valorización de un importante residuo agroindustrial generado ampliamente en la región sur de Brasil, el residuo de la palmera pupuña (Bactris gasipaes). Para ello, se han realizado ensayos de degradación de colorantes sintéticos mediante fermentación en estado sólido (FES) en presencia del hongo de podredumbre blanca Ganoderma lucidum EF 31 cultivado en el residuo de pupuña. El cultivo en estado sólido se realizó variándose las cantidades del residuo de pupuña (R), volúmenes de fase líquida (V) y concentraciones de colorante (C). El análisis de los datos experimentales muestra todos los factores considerados (V, C y R) afectan de forma significativa a la producción de la enzima lacasa y a la degradación de los colorantes. Experimentos realizados con el colorante Remazol Brilliant Blue R mostraron que la condición que conduce al mayor porcentaje de eliminación de color (97%) conduce igualmente a la mayor actividad lacasa. Adicionalmente, los datos experimentales indican la existencia de un efecto inhibitorio en el metabolismo fúngico al aumentar la dosis de los efluentes textiles. Por otra parte, se realizaron ensayos con diferentes tipos de hongos de podredumbre blanca para evaluar la eficacia de la fermentación de estado sólido frente a la fermentación sumergida y a la adsorción como estrategias para la decoloración de los efluentes textiles. El mayor porcentaje de decoloración (80%) se alcanzó a los 10 días de fermentación en estado sólido usando el hongo G. lucidum EF 31. De forma adicional, la eficacia de decoloración y la actividad de la enzima lacasa también fueron evaluadas en ensayos con biorreactores de 2 y 15 L de capacidad. Los altos valores de eficacia de descoloración obtenidos (superiores a 80%) ponen en evidencia la eficiencia del sistema propuesto. Por tanto, el uso del residuo de pupuña y el empleo del sistema FES proporciona un hábitat adecuado para el crecimiento del hongo G. lucidum y la consiguiente producción de lacasa, enzima necesaria para la degradación de los colorantes textiles.

The treatment of effluent from the textile industry is an important technological challenge. Decoloration of wastewater by traditional chemical, physical and biological methods presents as major drawbacks: the high costs, low efficiency and limited applicability. For these reasons, the purpose of this thesis is to have an interdisciplinary approach with innovative solutions to solve these problems. In addition, there is a valorization of an important agroindustrial residue generated largely in the southern region of Brazil, the residue of the pupunha palm (Bactris gasipaes). In these sence, degradation tests of synthetic dyes were carried out through solid state fermentation (SSF) in the presence of white rot fungi with pupunha residue. Solid state fermentation was performed under different operating conditions: amount of residue, volume of liquid phase and concentrations of dye. The experimental study of the data shows that the ligninolytic enzyme produced in greater quantity by G. lucidum the laccase. The control experiments performed with Remazol Brilliant Blue R (RBBR) showed that the condition with the highest percentage of color removal (97%) was conducted by laccase activity. For the experiments carried out with industrial effluents, the major activities of laccase were obtained in low concentrations of effluents, suggesting the existence of an inhibitory effect in the fungal metabolism. On the other hand, tests were carried out with different types of white rot fungi to evaluate the efficacy of solid state fermentation against submerged fermentation (SF) and adsorption as strategies for the decoloration of textile effluents. The highest percentage of decoloration (80%) was reached after 10 days of solid state fermentation using the fungus G. lucidum EF 31, and there were no significant differences in relation to the other two fungi. Therefore, it was concluded that the addition of pupunha residues and the use of the SSF system provide a suitable habitat for the growth of the fungus and the consequent production of the lacase enzyme, necessary for the effluent decoloration. These results were taken as a basis for the scale of the system, using first a reactor of 2 L of capacity and finally one of 15 L. These experiments, of 50 days, were realized with the fungus G. lucidum and the dye Remazol Brilhant Blue R (RBBR) and the efficacy of decoloration, laccase activity and pH inside the bioreactor were analyzed. The adsorption process was studied by characterizing the interactions between the functional groups present on the surface of the residue and the dye molecules using infrared Fourier transform (FTIR) spectroscopy. In the 2 L bioreactor, decoloration reached almost 80% and the laccase activity was 847.2 IU.mL-1. In the 15 L bioreactor, the decoloration reached 91%. In the adsorption studies performed with the pupunha residue, 50% of the color removal was achieved in the first 24 hours, but the decrease in the pH recorded in this experiment may be due to the growth of other microorganisms, which would contribute to the decoloration. The results of the solid state fermentation test, regardless of the size of the bioreactor used, clearly indicate that the G. lucidum fungus that grows on the pupunha residue has the ability to decolor the textile effluents, particularly those containing the RBBR dye.