title: Use of Bacillus thuringiensis supernatant from a fermentation process to improve bioremediation of chlorpyrifos in contaminated soils.
abstract: The aim of this research was to investigate the potential of a nutrient-rich organic waste, namely the cell-free supernatant of Bacillus thuringiensis (BtS) gathered from fermentation, as a biostimulating agent to improve and sustain microbial populations and their enzymatic activities, thereby assisting in the bioremediation of chlorpyrifos-contaminated soil at a high dose (70 mg kg(-1)). Experiments were performed for up to 80 d. Chlorpyrifos degradation and its major metabolic product, 3,5,6-trichloro-2-pyridinol (TCP), were quantified by high-performance liquid chromatography (HPLC); total microbial populations were enumerated by direct counts in specific medium; and fluorescein diacetate (FDA) hydrolysis was measured as an index of soil microbial activity. Throughout the experiment, there was higher chlorpyrifos degradation in soil supplemented with BtS (83.1%) as compared to non-supplemented soil. TCP formation and degradation occurred in all soils, but the greatest degradation (30.34%) was observed in soil supplemented with BtS. The total microbial populations were significantly improved by supplementation with BtS. The application of chlorpyrifos to soil inhibited the enzymatic activity; however, this negative effect was counteracted by BtS, inducing an increase of approximately 16% in FDA hydrolysis. These results demonstrate the potential of B. thuringiensis supernatant as a suitable biostimulation agent for enhancing chlorpyrifos and TCP biodegradation in chlorpyrifos-contaminated soils.
authors.affiliation: Research and Development Department, Minkab Laboratories, Av. 18 de Marzo No. 546, Col. La Nogalera, Guadalajara, Jalisco, P.O. Box 44470, Mexico. Electronic address: aea@minkab.com.
authors.forename: Angel E
authors.initials: AE
authors.lastname: Aceves-Diez
authors.affiliation: Microbiology School, University of Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia.
authors.forename: Kelly J
authors.initials: KJ
authors.lastname: Estrada-Castañeda
authors.affiliation: Microbiology School, University of Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia. Electronic address: laura.castaneda@udea.edu.co.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Castañeda-Sandoval
mesh_terms: D001413:Bacillus thuringiensis / Q000378:metabolism*; D001673:Biodegradation, Environmental; D004390:Chlorpyrifos / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D005285:Fermentation; D006801:Humans; D007306:Insecticides / Q000378:metabolism*; D011728:Pyridones / Q000378:metabolism; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*
chemical_list: D007306:Insecticides; D011728:Pyridones; D012989:Soil Pollutants; C012587:3,5,6-trichloro-2-pyridinol; D004390:Chlorpyrifos
keywords: Bioremediation; Biostimulation; Chlorpyrifos; Organic waste (Bacillus thuringiensis supernatant); Soil microbial activity