Abstract
Biotreatment of methylparathion was studied in aqueous mineral salts medium containing bacterial culture to demonstrate the potential of the novel strain of Pseudomonas aeruginosa mpd. A statistical Box–Behnken Design (BBD) of experiments was performed to evaluate the effects of individual operating variables and their interactions on the methylparathion removal with initial concentration of 1000 mg l-1 as fixed input parameter. The temperature (X1), pH (X2), reaction time (X3) and agitation (X4) were used as design factors. The result was shown that experimental data fitted with the polynomial model. Analysis of variance showed a high coefficient of determination value 0.9. The optimum biodegradation of MP in terms MP removal (Y1), COD removal (Y2) and TOC removal (Y3) were found to be 95.2 %, 82 % and 61.2 % respectively. The maximum growth (Y4) was 2.18 optical density (OD). The optimum biodegradation correspond to the factors combination of middle level of X1 (33 oC), X2 (7.0), X4 (150 rpm) and the highest level of X3 (96h). MP removal and its residues were detected using spectral analysis. The study demonstrates the optimum MP biodegradation potential of this strain could use MP as the sole Carbon/Phosphate source. BBD confirmed to be dependable in developing the model, optimizing factors and analyzing interaction effects. Data from this study will be helpful in the design of small-scale field experiments and subsequently an in situ methylparathion biotreatment system for field application.
Highlights
MATERIAL AND METHODSContinuous and excessive use of organophosphorus (OP) compounds has led to the contamination of several ecosystems in different parts of the world (Cisar and Snyder, 2000; Tse et al, 2004)
Box-behnken statistical experimental design was used to investigate the effects of the three independent variables on the response function and to determine the optimal conditions for maximizing the removal of methylparathion, chemical oxygen demand (COD), total organic carbon (TOC)
Results obtained during the present study showed the importance of using response surface methodology (RSM) based on the Box–Behnken Design (BBD) of experiment for the optimization of aqueous methylparathion biotreatment and degradation by potential microbial strains
Summary
Continuous and excessive use of organophosphorus (OP) compounds has led to the contamination of several ecosystems in different parts of the world (Cisar and Snyder, 2000; Tse et al, 2004). Thiophosphoric acid esters, such as parathion, methylparathion (MP) and tetrachlorvinphos, are hazardous pollutants and their accumulation in the environment is a recognized ecological threat (Kaloyanova and Tarkowski, 1981). Methods for their enhanced degradation are an urgent task of contemporary chemical technology and biotechnology. Industries manufacturing pesticides release wastewater in water bodies or land. Pseudomonas aeruginosa, Clavibacter michiganense (Subhas and Dileep, 2003), Arthrobacter atrocyaneus, Bacillus megaterium and Pseudomonas mendocina (Bhadbhade et al, 2002), Agrobacterium radiobacter (Horne et al, 2002), and other Pseudomonas species (Ramanathan and Lalithakumari, 1999) have been reported to degrade
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