Modified-zeolite-supported biofilm in service of pesticide biodegradation

The development of biofilms on modified natural zeolites was investigated with purpose to obtain biocomposites with biodegradation activity towards pesticides MCPA and glyphosate for potential application in bioaugmentation of polluted agricultural soils. Microbial communities were selected from agricultural pesticide-contaminated soil/water samples and enriched on basis of their ability to biodegrade the pesticides. In order to enhance affinity of microbial communities to the support material, the natural mineral zeolite was modified by nontoxic environmentally friendly cations (Li+, Na+, K+, NH4+, H+, Mg2+, Ca2+, Fe3+) by methods preserving its structure and characterised using powder XRD, surface area measurement and chemical composition analysis. Elaborated biocomposites were characterised using SEM and biodiversity analyses. Kinetics of degradation of pesticides by the biocomposites was studied in liquid media. Results showed that according to zeolite modifications, the microbial activity and biodiversity changed. Best pesticides biodegradation rate reached 0.12-0.13 mg/h with half life of 16-18 h, which is considerably quicker than observed in natural environment. Metagenomics on the 16S rRNA genes of the biofilm communities highlighted the selection of bacteria genera known to metabolise MCPA and glyphosate. Altogether, results suggested that zeolite do not only have a passive role of biofilm support, but also have protective and nutrient-supportive functions that consequently increase biodiversity of the pesticide degraders growing in the biofilm and influence the pesticide biodegradation rate.