Degradation of 2,4-dichlorophenoxyacetic acid by a halotolerant strain of Penicillium chrysogenum: antibiotic production

Abstract

The extensive use of pesticides in agriculture has prompted intensive research on chemical and biological methods in order to protect contamination of water and soil resources. In this paper the degradation of the pesticide 2,4-dichlorophenoxyacetic acid by a Penicillium chrysogenum strain previously isolated from a salt mine was studied in batch cultures. Co-degradation of 2,4-dichlorophenoxyacetic acid with additives such as sugar and intermediates of pesticide metabolism was also investigated. Penicillium chrysogenum in solid medium was able to grow at concentrations up to 1000 mg/L of 2,4-dichlorophenoxyacetic acid (2,4-D) with sucrose. Meanwhile, supplementation of the solid medium with glucose and lactose led to fungal growth at concentrations up to 500 mg/L of herbicide. Batch cultures of 2,4-D at 100 mg/L were developed under aerobic conditions with the addition of glucose, lactose and sucrose, showing sucrose as the best additional carbon source. The 2,4-D removal was quantified by liquid chromatography. The fungus was able to use 2,4-D as the sole carbon and energy source under 0%, 2% and 5.9% NaCl. The greatest 2,4-D degradation efficiency was found using α -ketoglutarate and ascorbic acid as co-substrates under 2% NaCl at pH 7. Penicillin production was evaluated in submerged cultures by bioassay, and higher amounts of β -lactam antibiotic were produced when the herbicide was alone. Taking into account the ability of P. chrysogenum CLONA2 to degrade aromatic compounds, this strain could be an interesting tool for 2,4-D herbicide remediation in saline environments.

Keywords:

• 2,4-dichlorophenoxyacetic acid
• xenobiotic
• antibiotic
• biodegradation
• Penicillium chrysogenum

Acknowledgements

This study was supported by a grant from the Faculty of Science and Technology of New University of Lisbon.