Fungal diversity and environmental herbicides remediation

The extensive use of pesticides in agriculture has prompted intensive research on chemical and biological methods in order to protect contamination of water and soil resources. Herbicides present chemical structures similar to natural compounds that are biodegradable, in spite of more complex, however their use in control and protection of crops is needed nowadays. Biodegradation is a fundamental attenuation process for pesticides in soil. The 2,4-dichlorophenoxyacetic acid (2,4-D) is a member of the chlorophenoxyacid herbicides, and its amine and esters formulations have been used for the crop, cereals, sugar cane, fruit trees, fields and forest plagues control. Studies have shown that 2,4-D could be biodegraded by soil microorganisms, in spite of mineralization process limiting the herbicide availability. The complete removal of the herbicide by microorganism(s) seems to be a promise way for elimination of 2,4-D under in situ conditions. A phenol degrading microorganism was isolated from soil samples of a salt mine. The isolate, Penicillium chrysogenum, was used to investigate the aerobic degradation of phenol and its derivates under high saline concentrations. P. chrysogenum CLONA2 was able to degrade high phenol concentrations in a simple minimal mineral medium with 5.9 % (w/v) NaCl. The products originated from phenol catabolism did not present toxicity. Microbiological methods were applied in order to investigate the effect of 2,4-D on P. chrysogenum CLONA2 growth. Biochemical and chemical methods were used as indicators of metabolic activity of CLONA2 in the presence of 2,4-D as the sole carbon source. Preliminary assays have shown that P. chrysogenum was able to growth at concentrations up to 1000 mg/L of 2,4-D under different osmotic pressure. No remarkable difference in the apical extension rate occurred at concentrations lower than 100 mg/l of 2,4-D with 2% (w/v) NaCl. However, for concentrations higher than 500 mg/l 2,4-D, a significant negative effect on CLONA2 growth was observed concomitant with an increase in the production of a red orange pigment possible due to toxic effect of 2,4-D. BOD and biomass data support the hypothesis of degradation and mineralization of 2,4-D by CLONA2. Since, catabolic pathways often require the investment of co-substrate or energy equivalents in the initial metabolic steps, as a way of gain of energy to pollutant degradation, a more efficient process of 2,4-D could be achieve using this strategy. Therefore, the data present in this study point to a higher possibility of P. chrysogenum CLONA2 to remediate 2,4-D pollution from soils and waters resources. P. chrysogenum CLONA2 may play an important ecological role in the degradation, mineralization and /or transport of 2,4-D.