BIODEGRADATION OF DIAZINON AND METHOMYL PESTICIDES BY WHITE ROT FUNGI FROM SELECTED HORTICULTURAL FARMS IN RIFT VALLEY AND CENTRAL PROVINCES, KENYA

  • A. B. Nyende Institute for Biotechnology research, Department of Biochemistry and Department of Botany Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya
  • J. Ochora Institute for Biotechnology research, Department of Biochemistry and Department of Botany Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya
  • G. Magoma, Institute for Biotechnology research, Department of Biochemistry and Department of Botany Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya
  • W. O. Nyakundi, Institute for Biotechnology research, Department of Biochemistry and Department of Botany Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya
Keywords: White rot fungi, methomyl, diazinon, metabolite and biodegradation

Abstract

White rot fungi are robust organisms and are generally more tolerant to high concentrations of polluting chemicals
than bacteria, they therefore present a powerful prospective tool in bioremediation. In this study, the potential for
biodegradation of methomyl and diazinon by white rot fungi through enrichment and isolation of methomyl and
diazinon biodegraders from horticultural soils was done. Five white rot fungal isolates WR1, WR2, WR4, WR9 and
WR15 were cultured in a medium containing methomyl and diazinon as the only carbon source and incubated at
280C and monitored for biodegradation at intervals of 10 days for a period of 100 days. Using Gilson HPLC system
with acetonitrile (75% sample: 25% acetonitrile) as the mobile phases. The biodegradation of methomyl and
diazinon overtime using fungal isolate mixtures, took 59 days while for individual isolates, it took a maximum of
100 days to biodegrade the pesticides. These proofs that fungal mixtures in soil fasten the rate of biodegradation
of pollutants compared to individual isolates. The pesticide methomyl was eluted at 4.9 minutes while the
methomyl metabolite was eluted at 4.1 minutes. Diazinon was eluted at 11 minutes while the diazinon
metabolites; diazoxon and oxypyrimidine were eluted at 2.3 and 2.6 minutes. The HPLC method used enabled the
separation and quantification of the pesticides in an HPLC run-time of 15 min. Results indicated that after 100 days
all the isolates managed to biodegrade the respective pesticides. The rate of mineralization or disappearance of a
pesticide was proportional to the concentration of the pesticide. White rot fungi are advantageous over bacterial
systems since these fungi can grow rapidly when supply of nutrients is low/limited.

Published
2019-05-16