Streptomyces sp. M7 immobilized cells as bioinoculant for enhanced atrazine removal in biobed-type biomixtures

Abstract

This work evaluates the use of actinobacteria immobilized as a strategy to inoculate biomixtures intended for biobeds for atrazine removal. Immobilization of the pesticide-degrading actinobacterium Streptomyces sp. M7 (M7) was carried out on different sugarcane by-products. Bagasse allowed the greater biomass of immobilized cells [(1.63 ± 0.20) x 107 CFU g− 1 ] and the maximum immobilization efficiency for M7 (81 %), compared to the other supports evaluated. Besides, a significantly higher proportion of M7 cells retained their viability by storing them at 4 ◦C and 30 ◦C up to 14 and 7 days, respectively, when immobilized in bagasse than when free. The bioaugmentation of two biomixtures formulated with sugar industry by-products was carried out with M7 immobilized in bagasse. Dissipation of ATZ (50 mg kg− 1 ) was significantly enhanced, reaching up to 57–69 %, and ATZ half-life (t1/2) was reduced by 2.6- to 14-fold in the biomixtures bioaugmented with immobilized M7, compared to the non-bioaugmented, confirming that bioaugmentation hastened the ATZ dissipation. Furthermore, the development of total heterotrophic microorganisms was higher in the bioaugmented biomixtures compared to the non-inoculated biomixtures, suggesting that the actinobacterium was able to colonize the biomixtures alongside the pesticide and the native microbiota. The presence of ATZ or the bioaugmentation did not negatively affect the overall microbial activity. Based on this, has great potential as a material for immobilizing actinobacteria, and the inoculation of biomixtures with this immobilized microorganism could be a promising tool to improve the dissipation of pesticides, such as atrazine, in biobeds.