Fipronil degradation kinetics and resource recovery potential of Bacillus sp. strain FA4 isolated from a contaminated agricultural field of Uttarakhand, India

Abstract This study investigates the potential role of Bacillus sp. FA4 for the bioremediation of fipronil in a contaminated environment and resource recovery of natural sites. The degradation parameters for fipronil were optimized using response surface methodology (RSM) with a pH of 7.0, a temperature of 32 °C, inocula 6.0×108 CFU·mL-1, at a fipronil concentration of 50 mg·L-1. Degradation of fipronil was confirmed in mineral salt medium (MSM), soil, immobilized agar discs, and sodium alginate beads. The degradation kinetics of fipronil in presence of FA4 indicated the enhanced degradation in a different medium. The significant reduction of half-life of fipronil suggested that strain FA4 could be used for the treatment of large-scale fipronil degradation from the environment. The kinetic parameters, such as qmax, Ks, and Ki for fipronil degradation with strain FA4, were 0.698 day-1, 12.08 mg·L-1, and 479.35 mg·L-1, respectively. Immobilized FA4 cells with sodium alginate and agar disc beads showed enhanced degradation with reductions in half-life at 7.83 and 7.34 days, respectively. The biodegradation in soil further confirmed the degradation potential of strain FA4 with a half-life of 7.40 days as compared to the sterilized soil control’s 169.02 days. The bioremediation potential of strain FA4 confirmed the importance of the bacterial strain in resource recovery from contaminated environments. The impacts of the strain FA4 on fipronil degradation under different in vitro conditions showed that the strain could be used for bioremediation and resource recovery of contaminated wastewater and soil in natural contaminated sites.