Enhanced degradation of prometryn and other s-triazine herbicides in pure cultures and wastewater by polyvinyl alcohol-sodium alginate immobilized Leucobacter sp JW-1

The s-triazine herbicides, such as prometryn, have been widely used in agriculture and have raised much public concern over their contamination of water and soil. Leucobacter sp. JW-1 cells were immobilized in polyvinyl alcohol sodium alginate (PVA-SA) beads and then used to degrade prometryn. Orthogonal array experiments showed that the optimal immobilization conditions of PVA-SA immobilized Leucobacter sp. JW-1 beads (PSLBs) were 3% JW-1 cells (w/v, wet weight), 10-12% (w/v) PVA, 2-3% (w/v) calcium chloride, and an immobilization time of 24-36 h. The PSLBs were more tolerance to pH, temperature and salinity changes than free JW-1 cells and were stable and effective for degrading prometryn through six reuse cycles without losing their degradation capacity. The half-life of prometryn degradation by PSLBs at 100 mg L-1 in pesticide plant wastewaters were 1.1-6.9 h. The rate constants of prometryn degradation by PSLBs in wastewaters ranged from 304 to 576 mg L-1 day(-1), which were approximately 1.25-118 times those of degradation by free JW-1 cells. The PSLBs degraded 99.9% of atrazine, 99.9% of ametryn, 97.8% of propazine, 100.0% of simetryn, 77.9% of simazine, 98.9% of terbuthylazine, 95.2% of prometon, 98.9% of atraton, and 31.6% of terbumeton at an initial concentration of 50 mg L-1 of each herbicide in 2 days. This study indicates that PSLBs persistently biodegrade s-triazine herbicides better than JW-1 free cells, and can be an efficient, safe and reusable biomaterial for the removal of striazine herbicides from contaminated sites. (C) 2017 Elsevier B.V. All rights reserved.