Abstract
Pleurotus fungi are basidiomycetes that stand out in the degradation of recalcitrant organic compounds such as lignin derivatives and phenolic compounds. The aim of this study was to make a comparative evaluation of the capacity of the Pleurotus ostreatus POS 560 and Pleurotus floridae PSP1 fungi in the degradation of 2,4 and 2,6-dinitrotoluene (DNTs) in effluent from an explosive factory. The characterization of the effluent indicated 318 mg L-1 of DNTs, 246 mg L-1 of COD and toxicity factor for Daphnia magna corresponding to 8. The conduct of a multivariate study estimated the influence of the variables pH (5.0 and 6.0), co-substrate concentration (10 and 20 g L-1 of glucose) and species of the fungus Pleurotus (ostreatus and floridae) on the degradation of DNTs, indicating that the variables Fungus and [Glucose] were significant (p <0.05) presenting effects in the order of + 4.45 ± 0.26 and -1.14 ± 0.26, respectively. The reproduction of the best efficiency conditions (P. floridae; pH 6.0 and 10 g L-1 of glucose) in agitated flasks (100 rpm, 26oC) was able to carry out, within 14 days of treatment, the removal of organic matter and toxicity factor in levels on the order of 55 and 50%, respectively, in addition to the complete degradation of DNTs which occurred in the first 120 hours of treatment. In this period, the maximum activity of the peroxidase and Mn-peroxidase enzymes was also characterized, suggesting high potential of the bioprocess under study for remediation of effluents contaminated with nitroaromatic compounds.
Highlights
The nitroaromatic explosives industry produces in its industrial process, especially in the purification stages, wastewater with significant polluting potential, a characteristic especially attributed to the presence of significant amounts of nitroaromatic compounds such as 2,4,6trinitrotoluene 2,4-dinitrotoluene, 2,6-dinitrotoluene mono and polysubstituted amino and nitrophenols, among others (Barreto-Rodrigues et al, 2009)
Equation 1 was generated considering only the significant coefficients listed in Table 2 and it explains mathematically how each variable affects the nitroaromatic compounds removal during the biological treatment of red water effluent
Regarding pH, its main effect was not significant, its interaction with the glucose illustrated by surface 1 (a) reveals better efficiency when the tests were conducted at the lowest glucose concentration and the highest pH level (6.0). These results show that even in treatments of different contaminants, there is a relationship in the efficiency presented by the fungi when influenced by pH and glucose as the study of Kunjadia et al (2016) shows, where the efficiency of biodegradation of three types of azo dyes was evaluated by three varieties of white degrading fungi of the genus Pleurotus, namely P. ostreatus, P. sapidus, and P. floridae, which respectively showed 88, 92 and 98% efficiency in decolorization in 10 days of treatment where the influence by the pH of the medium in the process of biosorption carried out by the fungi had the maximum removal, being achieved with pH varying between 6−6.5 and, outside of that, it was verified that the the removal rates reduce quickly
Summary
The nitroaromatic explosives industry produces in its industrial process, especially in the purification stages, wastewater with significant polluting potential, a characteristic especially attributed to the presence of significant amounts of nitroaromatic compounds such as 2,4,6trinitrotoluene 2,4-dinitrotoluene, 2,6-dinitrotoluene mono and polysubstituted amino and nitrophenols, among others (Barreto-Rodrigues et al, 2009). White degradation fungi decompose the three components of wood - lignin, cellulose, hemicellulose - at similar speeds This ability is because they produce several extracellular lignocellulolytic enzymes, mainly laccases, manganese peroxidase and versatile peroxidases, being able to act on several xenophobic compounds with lignolytic characteristics (Šrédlová et al, 2016). In comparison to the enzymatic system of many microorganisms, only the attack of white degrading fungi by specific enzymatic oxidative is able to cause mineralization by the cometabolic process of the aromatic nucleus of the C−TNT ring, which generates CO2 and
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