Abstract

HERNANDEZ CASTELLANOS, José Leonardo et al. BIODEGRADATION OF ORGANOPHOSPHATE AND ORGANOCHLORINE PESTICIDES BY Candida tropicalis AND Stenotrophomonas maltophilia IN SOIL MICROCOSMS. Rev. Int. Contam. Ambient [online]. 2021, vol.37, 53889.  Epub June 06, 2022. ISSN 0188-4999.  https://doi.org/10.20937/rica.53889.

For decades, organophosphate and organochlorine pesticides have been used in Mexico. Due to their persistence in the environment, they have caused damage to various ecosystems, accumulation in trophic chains and affectations to human health. Therefore, it is important to establish remediation protocols at contaminated sites with this type of compounds. In this report, the yeast Candida tropicalis and the bacterium Stenotrophomonas maltophilia were used in soil microcosms for degrading malathion, parathion, chlorpyrifos, aldrin, and lindane. Additionally, optimal growth parameters for both microorganisms at bioreactor level were determined. The initial concentration of pesticides was 130 mg/kg in 10 g of soil. The highest degradation by C. tropicalis was obtained for malathion (98.32 %) followed by lindane (81.01 %), and chlorpyrifos (74.23 %), while S. maltophilia degraded malathion (98.23 %), aldrin (80.17 %), and lindane (75.85 %). Regarding culture conditions for producing high cell densities at bioreactor level, a high biomass value (132 g/L) was obtained for C. tropicalis at 36 ºC, 140 rpm, pH 5 and an air intake of 2 vvm. In the case of S. maltophilia, a lower value (54 g/L) was obtained under the best culture conditions (28 ºC, 70 rpm, pH 5 and 2 vvm). The present work showed for the first time that C. tropicalis is capable of degrading some organophosphate and organochlorine pesticides, and due to its easy handling in liquid culture, it is proposed as a biological agent that can be used in the remediation of potentially pesticide-contaminated soils.

Keywords : biodegradation; organophosphates; organochlorine; Candida tropicalis; Stenotrophomonas maltophilia.

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