Anaerobic degradation of microcystin-LR by an indigenous bacterial Enterobacter sp. YF3

ABSTRACT

Microcystin-LR (MC-LR), a known hepatotoxin present in drinking water, and contaminated food and algal dietary supplements poses a threat to environmental and public health and thus needs to be removed. Previously microbial aerobic degradation was considered the predominant catabolic process for MC-LR inactivation, but the potential role of anaerobic microbes still needs to be determined. In our study an anaerobic MC-degrading bacterium Enterobacter sp. YF3 was isolated and identified that was capable of degrading MC-LR. Under optimal conditions the anaerobic Enterobacter sp. YF3 displayed a MC-degrading rate of 0.34 µg/ml/day. This process was dependent on temperature, pH and MC-LR concentration. Further the extracellular secretion of metabolites of anaerobic bacterium degraded MC-LR at 0.22 µg/ml/day. The parent MC-LR as well as two MC-degrading products was identified by high performance liquid chromatography (HPLC). The anaerobic MC-degrading Enterobacter sp. bacterium metabolized MC-LR independent of MC-degrading genes mlrABCD. Data indicate that anaerobic Enterobacter sp. YF3 produces MC-degrading products via a pathway that acts independently of mlrABCD genes which may add to the arsenal of bacteria to degrade microcystins.

KEYWORDS:

• Microcystin-LR
• biodegradation
• anaerobic
• Enterobacter

Additional information

Funding

This work was supported by the National Natural Science Foundation (81773393, 81502787); Central South University Innovation Driven Project (20170027010004); Key Research and Development Projects in Hunan Province (2019SK2041, 2018WK2013); Fundamental Research Funds for the Central Universities of Central South University (2018zzts858, CX20190241); The Ministry of Science and Technology of China (2015FY111100, 2016YFC0900802).