Bead-immobilized Pseudomonas stutzeri Y2 prolongs functions to degrade s-triazine herbicides in industrial wastewater and maize fields.

Functional durability of bio-augmented microbes in contaminated fields remains a major challenge in bioremediation. In the present study, various immobilization materials and compositional combinations were designed and compared to enhance the functional durability of Pseudomonas stutzeri sp. Y2 for degradation of simazine, one of the most used herbicides, in industrial wastewater and maize fields. Among four combinations of materials tested, the optimal combination obtained from the orthogonal array trials was 14% polyvinyl alcohol (PVA), 1-3% sodium alginate (SA), 2% activated carbon (AC), and 1-2% Y2 cells (PSC-Y2), which yielded 1.7 fold faster degradation of simazine at 50 mg L-1 than that by free Y2 cells in the industrial wastewater. The degradation half-lives (DT50) of simazine (10 mg L-1) by free Y2 cells and PSC-Y2 was 1.1 d and 5.3 d in laboratory soil, respectively. The DT50 of simazine by PSC-Y2 at the recommended and double dosages of simazine (0.45 and 0.9 g ai·m-2) was 17.2 d and 12.4 d in the maize fields, respectively, in comparison with 23 d and 17.4 d by free Y2 cells. In addition, the PSC-Y2 degraded 100% of atrazine and terbuthylazine, and 96% of propazine at an initial concentration of 50 mg L-1 each in 4 days. This study provides an immobilization strategy to stabilize bacteria and prolong bacterial functions to treat s-triazine herbicides contaminated water and soil.