Search

The colonization and biodegradation of the superabsorbent polymer component of water absorbing geocomposite by microorganisms occurring in the soil were investigated using a pot experiment. The polymer used in this study was technical cross-linked potassium polyacrylate (tKPA). It was placed inside a plastic skeleton structure covered with a polyester fabric sheath and incubated in non-sterile Haplic Luvisol soil sown with grass for nine months. After this time, we noticed a 77.88% reduction of 4.25 g of the tKPA initial dry mass. The highest number of soil microbes that colonized and utilized tKPA as the sole carbon and energy source was found after the first month of incubation. It ranged from 4.02 log10 CFU g−1 of water absorbed by tKPA for fungi and protists to 6.99 log10 CFU for bacteria; during the next eight months, the number decreased to 3.05 and 5.63 log10 CFU, respectively. Bacillus megaterium isolate 37SBG and the Acremonium sclerotigenum – Acremonium egyptiacum complex isolate 25SFG shown to possess the ability to degrade tKPA were selected among the microorganisms that colonized the superabsorbent polymer. After 60 days of incubation of these microorganisms in mineral media supplemented with tKPA as the sole nutrient source, 280.50 mg of the initial polymer dry mass declined by 30.28% and 20.50% for 37SBG and 25SFG, respectively. In addition, after 30 days of growth in a medium mimicking the composition of grass root exudates that was additionally enriched with ultra pure cross-linked potassium polyacrylate (upKPA), 17.21% of the 267 mg initial dry mass of upKPA was degraded by B. megaterium 37SBG. Enzymatic activity similar to lignin peroxidase appears to be connected with this process. The tKPA geocomposite component was also effectively colonized by phytopathogens from the genus Phytophthora. Their numbers ranged from 0.70 to 2.26 log10 CFU g−1 of water absorbed by tKPA after 5 and 12 months, respectively, of the geocomposite incubation in the soil. In addition, some colonized tKPA microorganisms were able to limit the multiplication of the pathogen. The mycelial growth of Phytophthora cactorum and Rhizoctonia solani was inhibited in the presence of the A. sclerotigenum–A. egyptiacum complex isolate 25SFG. We concluded that the colonization of tKPA by both microbes with the ability to biodegrade it and phytopathogenic oomycetes could limit the soil application of geocomposite as a plant growth support. The biodegradation of tKPA by soil bacteria, fungi, and protists seems to also be important for the reduction of the amount of polymer residues deposited in the soil. In addition, this study expands our knowledge about antagonistic interactions between polymer degrading microbes and soil-borne pathogens.