2,4-Dichlorophenoxyacetic acid herbicide degradation by isolated bacterial species from termite mound soil in Ethiopia
摘要
2,4-dichloro phenoxy acetic acid (2,4-D) is an ionizable herbicide; its residues are only minimally maintained by soil components, and they readily pollute surface and ground water. For these reasons, microbe-mediated biodegradation is a practical method to remove 2,4-D residues from polluted environments. In the current study, 5 different termite mound soil bacterial isolates capable of utilizing 2,4-D as their sole carbon and energy source were isolated by soil enrichment on minimal salt medium (MSM) containing 2,4-D. A one promising bacterial isolate was selected and identified as Enterobacter cloacae, based on biochemical characteristics and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The growth studies conducted on Enterobacter cloacae reveal that it can thrive within a broad pH range of 2 to 6 and a temperature range of 15 to 45 °C. However, the optimal conditions for its growth over a 24-hour period were observed at a pH of 3.5 and a temperature of 25 °C. Furthermore, adding Enterobacter cloacae with an inoculum size of 1 ml (3 × 108 CFU/ml) to agricultural leachate resulted in a significantly higher degradation rate of 90.4% compared to only 9.4% degradation in uninoculated agricultural leachate. This finding suggests that Enterobacter cloacae has the potential to be utilized for bioremediation through bioaugmentation in the cleanup of water contaminated with the herbicide 2,4-D.