微囊藻毒素降解菌的筛选、鉴定及其胞内粗酶液对藻毒素MCLR的降解

【目的】从巢湖底泥中分离筛选高效的藻毒素降解菌,并初步研究其胞内粗酶液降解藻毒素-LR(MC-LR)的特性,为水体中藻毒素污染的微生物治理提供有效的菌源与理论依据。【方法】利用富集驯化培养技术,以MC-LR为唯一碳源,分离筛选MC-LR降解菌,通过形态观察、生理生化实验及16S rRNA序列分析鉴定菌株,并考察其胞内粗酶液在不同条件下对MC-LR的降解特性。【结果】分离得到1株能高效降解MC-LR的菌株M6。分子鉴定结果表明,该菌株为蜡状芽胞杆菌(Bacillus cereus)。其降解MC-LR的活性物质为胞内酶,而且至少有3种酶参与了MC-LR的降解,它们是菌体本身的组织酶而非诱导酶。当反应体系pH值为8.0,胞内粗酶液浓度为404.9 mg/L,MC-LR的初始浓度为10 mg/L时降解率最高,16 h可达98.7%。【结论】分离出的MC-LR降解菌为蜡状芽胞杆菌,该菌株对MC-LR有较高的降解能力,并且酶促反应受到反应体系的pH值、胞内粗酶液浓度以及藻毒素初始浓度等因素的影响。

Screening and identification of a microcystin-degrading bacterium strain and its enzymatic degradation of microcystin-LR by intracellular extract of Bacillus cereus

Objective]To provide effective microorganisms for the treatment of water polluted by microcystins(MCs),the strains capable of biodegrading microcystin LR(MC-LR) were isolated from the sediment of Chaohu Lake.The degradation of microcystin-LR by the intracellular extracts of the strains were studied.Methods] The enrichment culture using MC-LR as the sole carbon source was utilized to isolate the microcystin-degrading strains.The isolated strain was identified according to the observation of morphology,the physiological and chemical tests and the analysis of 16S rRNA gene sequences.The degradation of MC-LR by the intracellular extracts was studied.Results] Strain M6 effectively degrading MC-LR was isolated and the strain M6 could grow utilizing MC-LR as the sole carbon source.Phylogenetic analysis based on 16S rRNA gene showed the similarity of 99% between strain M6 and Bacillus cereus.The experimental results suggest that the active substances for degrading MC-LR were the intracellular extracts which were the tissue enzymes of cells rather than induced enzymes.The degradation of MC-LR may be due to the catalytic effects of three enzymes.The degradation rate of 98.7% could be reached under the following conditions: pH 8.0,404.9 mg/L of intracellular extracts,and 10 mg/L of the initial concentration of MC-LR.Conclusion] Strain M6 which could biodegrade MC-LR efficiently was identified as Bacillus cereus.The influences of pH,the concentration of intracellular extracts and the initial concentration of MC-LR on the enzymatic reaction were obvious.