(21h) Biodegradation of the Fungicide Prochloraz Using a Microbial Consortium By FT-ICR Mass Spectrometry

Prochloraz (N-propyl-N-[2-(2,4,6-trichlorophenoxy)ethyl]imidazole-1-carboxamide) belongs to the imidazole class of fungicides, commonly used to manage foliar diseases caused by fungi such as Ascomycota and Fungi imperfecti. In regions like Mexico and the USA, wheat crops often face significant yield losses due to fungal infections, prompting the use of chemical fungicides in the absence of resistant crop varieties. However, the imidazole group in prochloraz is known to interact with non-target enzymes in vertebrates, interfering with steroid metabolism and functioning as an endocrine disruptor. In addition, pesticide contamination poses significant environmental and public health challenges due to improper use and insufficient regulation. These include degradation of soil and water quality, endocrine disruption, and potential carcinogenic effects due to its accumulation in food. A further concern is that prochloraz degrades into 2,4,6-trichlorophenol (TCP), a compound with even greater toxicity. In response to this issue, the present study aims to evaluate the potential of a previously adapted microbial consortium to biodegrade commercial prochloraz in a batch reactor system. The evaluation was conducted using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) to identify degradation products and propose possible biodegradation pathways. Additionally, Total Organic Carbon (TOC) analysis was employed to quantify the extent of mineralization of the pesticide.

In the current work, prochloraz degradation was studied in a batch reactor system where the initial pesticide concentration was set at 100 µg·mL⁻¹. The microbial consortium was cultivated in a minimal salt medium containing essential nutrients for survival and metabolism, with prochloraz as the sole carbon source. Prior to the main experiment, the microbial strains underwent a progressive adaptation phase, exposing them to increasing concentrations of prochloraz (from 10 µg·mL⁻¹ up to 100 µg·mL⁻¹). This gradual acclimatization enhanced their degradation capabilities and shortened the lag phase during the subsequent degradation experiment.

Throughout the biodegradation process, key parameters such as microbial biomass, pH, and dissolved oxygen levels were monitored to assess the health and activity of the microbial consortium. FT-ICR-MS analysis was used to measure prochloraz concentrations for kinetics and identify intermediate metabolites, offering insight into the metabolic pathways responsible for its breakdown. TOC analysis provided data on mineralization efficiency by measuring the conversion of organic carbon into inorganic end products such as CO₂ and H₂O.

The experimental results indicated that the microbial consortium exhibited outstanding degradation efficiency, achieving a 97.49% reduction in prochloraz concentration within 18 hours. The TOC analysis revealed a mineralization rate of 78.33%, confirming that a substantial portion of the pesticide was fully converted into inorganic compounds. Notably, the FT-ICR-MS analysis revealed the absence of TCP in the degradation products, indicating that this toxic intermediate was fully metabolized. Based on the metabolites detected over time, a biodegradation pathway was proposed. The pathway suggests efficient enzymatic breakdown of both prochloraz and TCP, supported by the detection of specific intermediate compounds. This supports the hypothesis that the microbial consortium has developed a specialized metabolic mechanism for detoxifying and fully degrading these compounds.

These findings underscore the potential of using microbial consortia as biotechnological tools for environmental remediation. The rapid and effective degradation of prochloraz, coupled with its substantial mineralization and the absence of TCP, highlights the feasibility of applying this approach to contaminated agricultural sites. These outcomes are particularly promising for sustainable farming practices and ecological restoration in areas affected by pesticide pollution.