Banca de DEFESA: ANNA GABRIELLY DUARTE NEVES

BIOTECHNOLOGICAL POTENTIAL OF Aspergillus FOR THE BIOREMEDIATION OF TEXTILE DYES

Azo dyes; Biomass reuse; Adsorption modeling; Sustainable treatment; Effluent decontamination.

The textile industry is one of the largest polluters of water bodies, with the release of effluents loaded with toxic dyes affecting aquatic and terrestrial biota. Conventional treatments are not effective at removing these contaminants, and their inadequacy leads to the persistence of harmful pollutants in the environment. Bioremediation, particularly with fungi like Aspergillus, offers a promising solution, being more efficient and sustainable in dye removal, thereby reducing environmental impact. This study explored the potential of Aspergillus fungi in decolorizing textile dyes. The first chapter provides a scientometric analysis of articles indexed in Web of Science, PubMed, and Scopus, revealing 174 documents over 26 years, indicating that while the topic is academically recognized, there is a low publication rate. Research has primarily focused on decolorization through biosorption and biodegradation, highlighting Aspergillus niger and Aspergillus flavus, along with a growing trend in the use of lignolytic enzymes and combined methods. Based on the data, trends and knowledge gaps were identified, which can guide future research. Chapter 2 follows a similar review approach but with a systematic methodology. This review addressed the potential of these fungi, evaluating mechanisms, optimizations, and the influence of physical-chemical and biological conditions. The search included PubMed, Web of Science, and Science Direct, where 25 research articles were assessed. Twelve Aspergillus species were described in dye decolorization, with azo and anthraquinone being the main classes remediated, achieving decolorization rates above 85%. Biodegradation was the primary mechanism identified, with laccase, lignin peroxidase, manganese peroxidase, and glucose oxidase as key enzymes. Chapter 3 concerns the decolorization of the tetra azo dye Direct Black 22 (DB22) using 15 Aspergillus strains. Aspergillus japonicus URM 5620, Aspergillus niger URM 5741, and Aspergillus niger URM 5838 were the most effective. Biomass, even without pelletization, efficiently removed the dye, with live biomass being 59% more effective than dead biomass. Decolorization was effective with 1g of biomass, removing over 90% of the dye in less than 60 minutes, and completely with 5g in 10 minutes. Biomass was successfully reused for three cycles, with A. niger URM 5741 being the most resistant. All decolorizations were completed within 2 hours, fully removing the dye under optimal conditions. Lastly, Chapter 4 applied Aspergillus tamarii Kita UCP 1279 biomass for decolorizing DB22, aiming to characterize the biomass for industrial applications. The best conditions for decolorization were pH 4, 30°C, 25-125 mg/L dye, and 3g biomass, achieving decolorization rates above 90%. Kinetic and isothermal modeling indicated that biosorption follows the pseudo-second-order model and Langmuir isotherm, suggesting monolayer chemisorption. Structural characterization revealed that binding sites are suitable for adsorbing anionic dyes like DB22. The biomass decolorized 67.12% of the dye solution after 5 consecutive cycles. The dye was partially desorbed by alkaline eluents, allowing for complete recycling of both the biomass and the dye. These results show that Aspergillus is not only efficient in removing toxic dyes but also serves as a viable, ecological, and promising solution for mitigating the impact of the textile industry on ecosystems.