Spent Mushroom Compost of Pleurotus ostreatus: A Tool to Treat Soil Contaminated with Endosulfan

Abstract

Composts especially spent mushroom composts (SMC) have been used for their ability to degrade toxic organic pollutants. Due to extreme toxicity, endosulfan (C₉H₆Cl₆O₃S) is categorized as a Category 1 pollutant by the U.S. EPA because of its well-reported carcinogenicity. This study was done to monitor the biodegradation potential of SMC against this pesticide. For this purpose, bioreactors (BRs) system was designed to mimic the field conditions. Soil within all four BRs contaminated with endosulfan was amended with four different treatments of SMC. Quantitative reduction in amount of endosulfan isomers was calculated using Gas Chromatography–Electron Capture Detector. For the monitoring of metabolites formed as a result of biodegradation, Gas Chromatography–Mass Spectrometry was used. Maximum attenuation was observed in BR₁ (fresh SMC and soil). In BR₂ when fresh SMC was added in sterilized soil, rate of removal was declined as compared to BR₁. In another bioreactor BR₃, where unsterilized soil was used with sterilized SMC, total reduction in quantity of endosulfan was less than BR₁ and BR₂. BR₄ (abiotic control) showed the least reduction suggesting the role of SMC and soil microbes. Degradation was well described using simple first-order kinetics which revealed that the active microcosm of BR₁ manifested least DT₅₀. Denaturation of either SMC(BR₃) or soil(BR₂) or both (BR₄) resulted in less biodegradation than BR₁.

Conflict of interest

The authors declare no conflict of interest.

Acknowledgments

We are very thankful to Dr. Ming Tien, Department of biochemistry and molecular biology, Pennsylvania State University for his technical support in lignolytic enzyme analysis and Shengzhong Su of Statistical Consultation Center, Pennsylvania State University for his guidance in statistical analysis and handling with Kinetics software.