Isolation and characterization of bacterial strains capable of growing on malathion and fenitrothion and the use of date syrup as an additional substrate

Abstract

Four bacterial strains capable of growing on two organophosphorus pesticides (malathion and fenitrothion) were isolated from activated sludge. Among these isolates, the species Stenotrophomonas maltophilia was found to be capable of using fenitrothion as the sole carbon and nitrogen source, and malathion as the sole carbon source. There appear to be no similar reported findings. A crude juice of dates was tested as an additional carbon source for malathion degradation. The biodegradability was significantly enhanced with the supplementation of date juice. The degradation efficiency of the pesticide tested at a concentration of 60 mg/L reached the maximum value of 89% in the presence of date juice at 30 g/L reducing sugar. Statistical screening of four operating parameters (initial biomass concentration, aeration rate, agitation and temperature) for biomass growth and for malathion degradation by acclimated indigenous activated sludge was carried out using a fractional factorial design.

Keywords:

• Activated sludge
• date juice
• degradation
• fenitrothion
• malathion

Acknowledgements

The authors thank the anonymous reviewers and the Editor for valuable inputs to this paper.