Evaluation in the performance of the biodegradation of herbicide diuron to high concentrations by Lysinibacillus fusiformis acclimatized by sequential batch culture

Abstract

We evaluated and characterized the biodegradation of the herbicide diuron in its commercial form above its saturation concentration by Lysinibacillus fusiformis acclimatized by sequential batch culturing. Acclimatization was carried out in eight cycles in liquid culture, improving the capacity of L. fusiformis to remove diuron from 55.13 ± 1.3% in the first batch to 87.2 ± 0.11% in the eighth batch. Diuron biosorption was characterized with Langmuir and Freundlich isotherms, obtaining a maximum biosorption (q_max) of 0.00885 mg mg^-1. In diuron biodegradation assays, a consumption substrate biomass yield (Y_SD/X) of 6.266 mg mg^-1 was obtained, showing that biodegradation was the main mechanism in diuron removal. Diuron biodegradation by L. fusiformis was characterized by the Monod model, with a maximum specific growth rate (μ_max) of 0.0245 h^-1 and an affinity constant (K_SD) of 344.09 mg L^-1. A low accumulation of 3,4-dichloroaniline with the production of chloride ions indicated dechlorination when diuron was present at high concentrations. A phytotoxic assay conducted with Lactuca sativa showed that the toxicity of an effluent with diuron at 250 mg L^-1 decreased when it was pretreated with acclimatized L. fusiformis. Acclimatization by sequential batch culturing improved the ability of L. fusiformis to biodegrade diuron at high concentrations, showing potential in the bioremediation of diuron-contaminated sites.

Keywords: Acclimatization; Biodegradation; Biosorption diuron; L. fusiformis.