If effluents are released without treatment, the industrial chemicals in the surroundings will lead to environmental pollution. To prevent this, wastewater treatment has become common practice and numerous systems have arisen. Specifically, in the fruit packaging industry the chemicals found in wastewater are typically from fungicides and pesticides. To combat the high concentration of a certain fungicide, a depuration system based on pesticide<!–[if supportFields]> XE “pesticide” <![endif]–><!–[if supportFields]><![endif]–> adsorption was patented and the result was a reduction of that fungicide by 7000 times. However, the costs for implementing this system on a large scale basis are too great to be efficient. Similarly, a filter system to treat this wastewater removed more than 98% of certain fungicides; however, its implementation was also impractical in terms of cost and volume capacity. Panagiotis et al. (2011) recognize the need for a viable option; therefore, they suggest the bioremediation of these chemicals by fungi. Irreversible chemical degradation by microbes has already been studied. It is known that white rot fungi (WRF) can degrade various organic pollutants. Aspergilus niger<!–[if supportFields]> XE “Aspergilus niger” <![endif]–><!–[if supportFields]><![endif]–> has also been shown to degrade several pesticides. This study focuses on the bioremediation by these two types of fungi on fungicides and pesticides in the wastewater of the fruit packaging industry. Another aim is to increase the understanding of the enzyme’s role in this degradation process.—Daniella Barraza
Panagiotis, K., Perruchan, C., Exarhou, K., Ehaliotis, C., Karpouzas, D., 2011. Potential for bioremediation of agro-industrial effluents with high loads of pesticides by selected fungi. Biodegradation 22, 215–228.
Panagiotis et al. used A. niger and three different types of WRF: Phanerochaete chyrsosporium<!–[if supportFields]> XE “Phanerochaete chyrsosporium” <![endif]–><!–[if supportFields]><![endif]–>, Trametes versicolor<!–[if supportFields]> XE “Trametes versicolor” <![endif]–><!–[if supportFields]><![endif]–>, and Pleurotus ostreatus<!–[if supportFields]> XE “Pleurotus ostreatus” <![endif]–><!–[if supportFields]><![endif]–>. From the WRF, the enzymes lignin<!–[if supportFields]> XE “lignin” <![endif]–><!–[if supportFields]><![endif]–> peroxidase (LiP), Mn dependent peroxidas (Mn), and laccase (Lac) can be studied since WRF has an extracellular enzymatic system called lignin mineralizing enzyme (LME) system that produces these three enzymes. The pesticides used were CHL, TBZ, OPP, IMZ, DPA, and TM. The evaporated residues of these pesticides were place in two different media selected to mimic the natural environment of the fungi. The first is a soil extract medium (SEM) and the second is straw extract medium (StEM). The soil in SEM is sandy loam with a pH of 6.5. StEM is composed of the supernatant of chopped and sterilized wheat straw and has a pH of 5.5. For the experiment, flasks were divided into two categories: non-inoculated and inoculated. The non-inoculated flasks contained either medium and evaporated residues of one pesticide<!–[if supportFields]> XE “pesticide” <![endif]–><!–[if supportFields]><![endif]–>. The inoculated flasks allowed a strain of fungi to grow before adding pesticides on the third day. After this addition, samples were taken in set intervals until 30 days had passed. Another part to this experiment was to investigate the ability of T. versicolor to degrade really high concentrations of the fungicides TBZ, OPP, IMZ, and DPA; and its ability to degrade mixtures of these pesticides as would be expected from the fruit packaging industry such as the post-harvest treatment of citrus fruits which would contain TBZ, OPP, and IMZ. For the enzymatic portion of the experiment, pesticide-free flasks were made for comparison to determine if pesticides have an effect on the enzymes.
In StEM, WRF degraded most of the pesticides. T. versicolor and P. ostreatus almost completely degraded DPA and TM within the first two days. P. chyrsosporium had a slower rate of degradation for the same pesticides and was not able to degrade OPP. In non-inoculated flasks, the rate of degradation for all of the pesticides was much slower around 50% and 80% slower for DPA and TM, respectively. In SEM, the results were slightly different. Within the first two hours, T. versicolor and P. ostreatus were able to completely degrade DPA, TM, and OPP. However, WRF did not degrade IMZ in SEM whereas it had completely degraded it in StEM. The reason is because WRF are adapted to ligninocellulosic material like straw and not soil. P. chrysosporium and A. niger rapidly degraded DPA. A. niger, however, despite being in a medium similar to its natural environment had the slowest degradation rate for OPP comparable to the degradation rate in the controlled flask. In both SEM and StEM, activity for the enzyme LiP was not detected. Activity for the enzymes MnP and Lac were detected in flasks containing T. versicolor and P. ostreatus. There was a positive trend between the rapid degradation of DPA and OPP by T. versicolor and P. ostreatus and the activity of MnP and Lac which suggests that the enzymes play a strong role in degradation. A reason for this is because MnP and Lac are known to oxidize phenol rings of lignin<!–[if supportFields]> XE “lignin” <![endif]–><!–[if supportFields]><![endif]–> and these two pesticides contain phenol rings in their molecules. This result further suggests that other enzymes are responsible for the rapid degradation of other pesticides. Finally, T. versicolor was able to degrade high concentrations of pesticides and mixtures of pesticides except with a few discrepancies the reasons which remain unknown. WRF, especially T. versicolor and P. ostreatus, had the best records for degradation of pesticides and can serve as depuration systems for the fruit packaging industrial wastewater.