Zeolite-supported biofilms as inoculants for the treatment of MCPA-polluted soil and sand by bioaugmentation: A microcosm study

In this study, the effectiveness of bioaugmentation approach using zeolite supported biofilms as inoculants was evaluated in microcosm experiments. For this, selected MCPA-degrading microbial consortium was grown as biofilm on natural and Fe-modified zeolite grains (0.2–1.25 mm in size) and the obtained biocomposites (4 × 1010 cells/g of biocomposite) were amended to soil or sand microcosms (130 g biocomposites/m2; 4 × 107 cells/g of dry weight soil or sand) supplemented with herbicide MCPA (2-methyl-4-chlorophenoxyacetic acid, 0.166 mg/kg dw soil or 0.309 mg/kg of dw sand, respectively). The major part of the identified bacterial sequences (51–59 %) in both biocomposites was attributed to the bacterial genera related to biodegradation of pesticides, including phenoxy-herbicides (Cupriavidus, Novosphingobium, Pseudomonas, Rhodococcus, Sphingobium, Sphingopyxis). The present study showed that the MCPA biodegradation ability of the studied biocomposites was very close to each other and characterised with similar kinetics: biodegradation of 80 % MCPA within 2 days in soil and 5 days in sand. Thus, the zeolite-supported biofilms could be effective inoculants for pesticide biodegradation at polluted agricultural sites. The biocomposites can be effectively used not only for treatment of soil but also sand, however its activity may change with variation of the matrix. Surface modifications of a given support material is an interesting approach to select different microbial communities, which can provide significant advantages according to the site to be treated.