Actinobacteria bioaugmentation and substrate evaluation for biobeds useful for the treatment of atrazine residues in agricultural fields.

Biopurification systems (BPS) or biobeds are bioprophylaxis systems to prevent pesticide point-source contamination, whose efficiency relies mostly on the pesticide removal capacity of the biomixture, the majority component of a BPS. The adaptation of the components of the biomixtures to local availabilities is a key aspect to ensure the sustainability of the system. In this work, the removal of atrazine (ATZ) was evaluated in biomixtures formulated with three sugarcane by-products as alternative lignocellulosic substrates. Based on the capacity of actinobacteria to tolerate and degrade diverse pesticides, the effect of biomixtures bioaugmentation with actinobacteria was evaluated as a strategy to enhance the depuration capacity of biobeds. Also, the effect of ATZ and/or the bioaugmentation on microbial developments and enzymatic activities were studied. The biomixtures formulated with bagasse, filter cake, or harvest residue, reached pesticide removal values of 37-41% at 28 d of incubation, with t1/2 between 37.9 ± 0.4 d and 52.3 ± 0.4 d. The bioaugmentation with Streptomyces sp. M7 accelerated the dissipation of the pesticide in the biomixtures, reducing ATZ t1/2 3-fold regarding the controls, and achieving up to 72% of ATZ removal. Atrazine did not exert a clear effect on microbial developments, although most of the microbial counts were less in the contaminated biomixtures at the end of the assay. The bioaugmentation improved the development of the microbiota in general, specially actinobacteria and fungi, regarding the non-bioaugmented systems. The inoculation with Streptomyces sp. M7 enhanced acid phosphatase activity and/or reversed a possible effect of the pesticide over this enzymatic activity.

Enhanced bioremediation of lindane-contaminated soils through microbial bioaugmentation assisted by biostimulation with sugarcane filter cake.

Lindane is a toxic and persistent organochlorine pesticide, whose extensive use generated its accumulation in different environmental matrices. Bioremediation is a promising technology that can be used combining bioaugmentation and biostimulation processes to soil restoration. The aim of the present work was to determine the conditions of maximum lindane removal by bioaugmentation with an actinobacteria consortium and biostimulation with sugarcane filter cake (SCFC). The assays were carried out on lindane-contaminated silty loam (SLS), clayey (CS), and sandy (SS) soils. Through complete factorial designs, the effects of three abiotic factors (moisture content, proportion and size of SCFC particles) were evaluated on lindane removal. In addition, a response optimizer determined the optimal conditions for pesticide removal in bioaugmented and biostimulated soils, in the range of levels studied for each factor. In these conditions, bioaugmentation of biostimulated soils increased the pesticide removal (SLS: 61.4%, CS: 70.8%, SS: 86.3%), heterotrophic microbial counts, and soil enzymatic activities, and decreased lindane T1/2, regarding the non-bioaugmented biostimulated controls, after 14 days of assay. The values of these parameters confirmed the efficiency of the bioremediation process. Finally, the viability of the four strains was demonstrated at the end of the assay. The results indicate that the simultaneous application of bioaugmentation with the actinobacteria consortium and biostimulation with SCFC constitutes a promising tool for restoring soils contaminated with lindane, by using the optimal conditions obtained through the factorial designs.

Lindane dissipation in a biomixture: Effect of soil properties and bioaugmentation.

The biomixture is the major constituent of a biopurification system and one of the most important factors in its efficiency; hence the selection of the components is crucial to ensure the efficient pesticides removal. Besides, bioaugmentation is an interesting approach for the optimization of these systems. A mixed culture of the fungus Trametes versicolor SGNG1 and the actinobacteria Streptomyces sp. A2, A5, A11, and M7, was designed to inoculate the biomixtures, based on previously demonstrated ligninolytic and pesticide-degrading activities and the absence of antagonism among the strains. The presence of lindane and/or the inoculum in the biomixtures had no significant effect on the development of culturable microorganisms regardless the soil type. The consortium improved lindane dissipation achieving 81-87% of removal at 66 d of incubation in the different biomixtures, decreasing lindane half-life to an average of 24 d, i.e. 6-fold less than t1/2 of lindane in soils. However, after recontamination, only the bioaugmented biomixture of silty loam soil enhanced lindane dissipation and decreased the t1/2 compared to non-bioaugmented. The biomixture formulated with silty loam soil, sugarcane bagasse, and peat, inoculated with a fungal-actinobacterial consortium, could be appropriate for the treatment of agroindustrial effluents contaminated with organochlorine pesticides in biopurification systems.