Biodegradation of diazinon and methomyl pesticides by white rot fungi from selected horticultural farms in Rift Valley and Central Kenya

Abstract

The aim was to investigate the potential for biodegradation of methomyl and diazinon (pesticides) by white rot fungi through enrichment and isolation of methomyl and diazinon biodegraders from horticultural soils. Five white rot fungal isolates labeled WR1, WR2, WR4, WR9 and WR15 were cultured in a medium containing methomyl and diazinon pesticides as the only carbon source and incubated at 280C and monitored for biodegradation at intervals of 10 days for a period of 100 days. Gilson HPLC system was used for the separation and quantification of the pesticides. The pesticide methomyl was detected at 4.9 minutes while the methomyl metabolite was detected at 4.1 minutes. Diazinon was detected at 11 minutes while the diazinon metabolites; diazoxon and oxypyrimidine were detected at 2.3 and 2.6 minutes. The rate of biodegradation of pesticides was much higher for mixtures of fungi (approximately 50 days) compared to individual isolates (60- 100 days) for diazinon while methomyl was 22-25 days. This shows that fungal mixtures in soil fasten the rate of biodegradation of pollutants compared to individual isolates. The isolates are good biodegraders due to their ability to degrade methomyl or diazinon hence making the isolates good agents for bioremediation. The authors recommend more studies to be done in the fields before their potential application by farmers.