Carbofuran is frequently applied to crop fields to combat insects globally causing serious environmental pollution. In this study, the enhanced degradation of carbofuran in soil by augmentation with Bacillus sp. DT1 was determined. The results showed that the augmentation with the bacterial strain increased the degradation by almost 30% compared to attenuation after 30 days at an initial concentration of 10 mg/kg dry soil. The half-life values of the insecticide were 41.6 and 17.9 days for attenuation and augmentation, respectively. Moreover, the augmentation with Bacillus sp. DT1 significantly increased sequence numbers of 16 S rRNA in soil compared to the initial stage. However, α-diversity indices, i.e., values of OTUs, ACE, Chao1 and Shannon showed no statistical differences in soil with and without the insecticide addition, with and without augmentation after 30 days. These results showed that carbofuran did not inhibit or stimulate the growth of soil bacteria at 10 mg/kg dry soil.
Pseudomonas fluorescens HH isolated from soil utilized 2,4-Dichlorophenoxyacetic acid (2,4D) as a sole carbon and energy source. The strain completely utilized 1.0 mM of 2,4D within 30 hr. The immobilized Pseudomonas fluorescens HH degraded 2,4D with higher rates compared to the rates of free-suspension cells. The determination of degradation and cell growth kinetics in exponential growth phase of bacteria showed that both fitted with the Edwards model, in which the maximal utilization rates and inhibition coefficient were 0.079 ± 0.008 mM/h and 0.820 ± 0.03 mM, respectively. The addition of glycerol as a cryoprotectant into alginate increased the survival of bacteria in beads during freeze-drying process, which resulted in reducing the adverse effects of bead lyophilization.
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