Microcystin-LR biodegradation by Sphingopyxis sp. USTB-05

Abstract

A promising bacterial strain for biodegrading microcystin-LR (MC-LR) as the sole carbon and nitrogen source was successfully isolated from Lake Dianchi, China. The strain was identified as Sphingopyxis sp. USTB-05, which was the first isolated MCs-biodegrading Sphingopyxis sp. in China. The average biodegradation rate of MC-LR by Sphingopyxis sp. USTB-05 was 28.8 mg·L^-1 per day, which was apparently higher than those of other bacteria reported so far. The optimal temperature and pH for both strain USTB-05 growth and MC-LR biodegradation were 30°C and 7.0, respectively. The release of MC-LR from the cyanobacterial cells collected from Lake Guishui and the biodegradation of MC-LR by both strain and cell-free extract (CE) were investigated. The results indicated that MC-LR with the initial concentration of 4.0 mg·L^-1 in water was biodegraded by Sphingopyxis sp. USTB-05 within 4 d, while MC-LR with the initial concentration of 28.8 mg·L^-1 could be completely removed in 3 h by CE of Sphingopyxis sp. USTB-05 containing 350 mg·L^-1 protein. During enzymatic biodegradation of MC-LR, two intermediate metabolites and a dead-end product were observed on an HPLC chromatogram. Moreover, the similar scanning profiles of MC-LR and its metabolic products indicate that the Adda side-chain of MC-LR was kept intact in all products.

Keywords

microcystin-LR(MC-LR) / biodegradation / Sphingopyxis sp / USTB-05 / cell-free extract

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Acknowledgements

The first and second authors did same contribution to this paper. This work was supported by the National Natural Science Foundation of China (Grant No. 203777008), State Key Joint Laboratory of Environment Simulation and Pollution Control (No. 09K08ESPCT), and Educational Committee of Beijing.

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