Degradation characteristics and soil remediation of thifensulfuron-methyl by immobilized Serratia marcecens N80 beads

Abstract

Microbial degradation is one of the effective methods to remove thifensulfuron-methyl (TSM) in soil and water environments. In this study, a high-efficiency TSM degrading strain Serratia marcecens N80 was used. The abandoned fungus substrate was converted to biochars at various pyrolysis temperatures (300, 450 and 600 °C). Biochar made at 600 °C (BC600) showed the best TSM adsorption capacity, while strain N80 adsorption efficiency reached the maximum up to 81.08%. Therefore, BC600, polyvinyl alcohol (PVA), and sodium alginate (SA) were chosen to establish an immobilized system for strain N80. The immobilized N80 beads (IN80) showed significantly improved reusability and storage stability. Under the optimal condition (pH 7.0, 35 °C, 1.5 × 108 cfu/mL), TSM (50 mg/L) degradation rates by free N80 and IN80 were 83.47 and 89.37% within 48 h, respectively. Free N80 and IN80 accelerated TSM degradation in soil, reducing its half-life to 6.13 d and 4.36 d, respectively. However, immobilized material beads (IM) slightly delayed the soil TSM degradation. TSM activated catalase and dehydrogenase but inhibited invertase and urease. IN80 treatment accelerated the recovery of invertase and urease. Moreover, IN80 accelerated the recovery of bacterial and fungal populations; the beneficial genera inhibited by TSM such as Sphingomonas, Lysobacter, Massilia, Rhodanobacter, and Gemmatimonas also increased to varying degrees. Meanwhile, IN80 showed an excellent inhibitory effect on pathogenic fungi (Fusarium and Alternaria), while increased the relative abundance of Mortierella, and the soil resistance to diseases. This study offers a potential in situ remediation strategy to improve the quality of the soil environment.