AAC  >> Vol. 8 No. 3 (August 2018)

    微囊藻毒素的危害及其分析方法进展
    The Harmful Effects of Microcystins and the Analytical Methods

  • 全文下载: PDF(862KB) HTML   XML   PP.91-102   DOI: 10.12677/AAC.2018.83012  
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作者:  

钟 力,徐文琦,胡静文,张大海:海洋化学理论与工程技术教育部重点实验室(中国海洋大学),山东 青岛

关键词:
微囊藻毒素研究现状生态风险去除方法Microcystins Research Status Ecotoxicity Removal Method

摘要:

微囊藻水华可产生微囊藻毒素,严重威胁生态系统。人类活动的日益加剧使得大量的氮、磷等营养盐排入淡水水体,加剧了水华的爆发。本文综述了国内外微囊藻毒素的产生及其危害和去除方法,重点关注了其分析方法和未来可能的研究方向。

The metabolites produced by the Microcystis blooms are called microcystins and pose a great threat to the ecosystem. Industrial and agricultural activities cause a large amount of nitrogen and phosphorus nutrients to be discharged into freshwater bodies and leading to the outbreak of water blooms. This review summarizes the research status on the generation, ecotoxicology and removal methods of microcystins at home and abroad, especially focusing on analysis method and proposes prospects for future research perspective.

1. 引言

我国是一个多湖泊与河流的国家,近年来随着湖泊、水库和河流等淡水水体周边工农业生产迅速发展,排入这些淡水水体的氮、磷等营养物质增多,造成水体的生态结构和功能发生变化,导致这些淡水水体富营养化(Eutrophication)。在一定的温度、光照等条件下,富营养化使水体中的藻类过量生长繁殖,造成水华(Water Bloom)的污染现象 [1] 。当水体中的营养物质被藻类消耗至无法支持其生存,藻类开始大量死亡,藻细胞破裂可能释放各种藻毒素,对生物的生存造成威胁,甚至导致水生态系统更深层次的崩溃 [2] 。监测数据显示,我国多个省市的水样含有不同程度的藻毒素污染,其中沟塘水、河水和水库水的污染最为严重 [3] 。如云南滇池、江苏太湖和安徽巢湖富营养化现象突出,相继爆发严重的蓝藻水华 [4] ;长江、黄河中下游的湖泊、水库等资源开发利用活跃的淡水水体也发生过不同程度的水华污染现象,并且在水体中检测出多种藻毒素 [5] [6] 。

在富营养淡水水体中,水华的爆发主要是蓝藻门的一个或几个属过度繁殖造成的,而微囊藻水华因具有爆发普遍、持续时间长和产生毒素多的性质,是淡水水体中危害最严重的一类 [7] 。微囊藻爆发性繁殖产生的初级代谢物被称为微囊藻毒素(Microcystins, MCs) [8] ,其毒性强烈,分布广泛,是藻毒素中危害最深远、影响最广泛的一类。水体含有50 mg/L浓度的MCs,可以完全抑制灰色念珠藻和鱼腥藻的生物活动并使其细胞死亡溶解 [9] ;MCs对大鼠的致死量LD50范围在36~122 μg/Kg [10] ;一定浓度的MCs还会诱使个体畸形生长、细胞癌变 [11] 。

人类直接接触MCs污染水体可引发皮肤炎、结膜炎和鼻炎,口服摄入会引发肠胃炎和急性肝炎等病症。MCs中毒事件有:1975年,美国宾夕法尼亚州Sewickley饮用水源受蓝藻污染,导致当地大约8000人出现急性肠胃炎 [12] ;1983年,澳大利亚Malpas地区大量居民罹患急性肝炎,经调查很可能是当地饮用水受蓝藻污染所致 [13] ;1991年,英国Rudyard湖爆发蓝藻水华,一支部队在附近训练后,多名士兵中毒 [14] ;1996年,巴西Caruaru城水库爆发蓝藻藻华,引起当地60人死亡 [15] 。在我国,每年约10万人死于原发性肝癌 [16] ,其中广西扶绥、江苏海门和启东的发病率比全国平均水平高8倍,流行病学调查认为这与当地多数居民饮用的浅塘水和河水长期含有MCs有一定关联 [17] 。

MCs危害巨大,逐渐引起世界各国和组织的关注,纷纷出台相应文件应对。世界卫生组织(WHO) 1998年补充了饮用水质量基准,规定MC-LR (游离态及细胞结合态)的安全阈值为1 μg/L [15] 。我国在2001年新修订的《生活饮用水卫生规范》将MC-LR列入非常规监测项目 [18] ,《城市供水水质标准》(CJ/T206-2005)规定MC-LR含量不得超过1 μg/L [19] 。人类活动导致全球淡水水体富营养化程度逐年增加,水华污染的爆发频率增加。因此,如何减少水体富营养化、控制藻类过分生长繁殖和有效去除藻毒素等环境问题成为环境科学领域的研究焦点。

2. 微囊藻毒素的产生

MCs是一种在藻细胞内合成的细胞内毒素,由肽合成酶复合体(Peptide synthesiscomplex)生成,具有生物活性和免疫抑制作用 [20] 。MCs作为藻种的初级代谢产物,由铜绿微囊藻(Microcystis aeruginosa)产生,其他如绿色微囊藻(M. viridis)、惠氏微囊藻(M. wesenbergii)和部分蓝藻,如鱼腥藻(Anabaena)、念珠藻(Nostoc)、颤藻(Oscillatoria)也能产生这种有毒化合物 [21] 。MCs的功能之一是与进入藻细胞内的重金属离子发生络合反应以避免重金属中毒 [22] ,二是抑制其他竞争的水生生物以创造有利于自身的生长环境 [9] ,当环境有利于藻种生长时,MCs合成较少,当环境因素不利于藻种生存,MCs的合成率增加,原因可能与藻种适应环境的调节行为有关。环境因素通过直接影响肽合成酶复合体的活性从而影响藻毒素的合成,例如Fe2+能够提高肽合成酶复合体的活性,促进MCs生成 [23] 。

MCs的合成受到光照、温度、pH和营养元素等环境因素的影响。Dai等 [24] 认为环境因素会影响微囊藻的腺苷酸能荷,从而影响藻细胞的代谢活动,调节MCs的合成,其中光照和营养元素的作用最大。Gorham [25] 的研究表明温度对MCs的毒性影响最大,在25℃环境下生成的MCs毒性最强。而Watanabe等 [26] 的研究指出光照对MCs毒性的影响比温度更大。Van der Westhuizen等 [27] 检测了M. aeruginosa UV-006株藻在不同温度和光照下合成藻毒素的毒性,发现温度和光照对毒性均有影响,但温度占主导作用。Utkilen等 [28] 发现高光照强度下,温度对MCs的合成几乎没有作用;而低光强下,温度才会影响MCs合成。综合目前的文献,环境因素对微囊藻细胞的代谢活动具有作用,从而影响MCs的产生,但不同环境因素的确切的影响途径及影响程度的大小,尚无明确的答案。

3. 微囊藻毒素的理化性质

MCs是一类七肽单环化合物,基本结构是七个氨基酸连接形成七肽单环,并带有一个侧链,如图1(a)所示。分子结构中编号为1~7的氨基酸分别是:1) D-丙氨酸(D-alanine, D-Ala),2) 可变氨基酸X,3) 甲基天冬氨酸(Methylaspartic acid, MeAsp),4) 可变氨基酸Y,5) Adda氨基酸,6) D-谷氨酸(D-glutamic acid, D-Glu),7) N-甲基脱氢丙氨酸(N-methyl dehydroalanine, Mdha) [29] 。其中,Adda (3-氨基-9-甲氨基-2,6,8-三甲基-10-苯基癸-4,6-二烯酸)是一种特殊的含有20个碳原子的β-氨基酸,是MCs表达生物活性所必须的特征结构 [30] 。由于可变氨基酸X和Y是两个不同的L-氨基酸,并且位置(3)的甲基天冬氨酸和(7)甲基脱氢丙氨酸的甲基化/去甲基化能产生差异 [10] ,使MCs拥有超过90种变体 [31] 。当可变氨基酸X和Y分别是亮氨酸(Leucine)和精氨酸(Arginine)时,即微囊藻毒素-LR (Microcystin-LR, MC-LR) [32] ,如图1(b)所示。

MCs的相对分子质量约为1000,性质稳定,不挥发,加热至100℃左右不失活,易溶于水,在水中的溶解度达到1 g/L以上。MCs对pH有一定缓冲作用,因其分子结构含有氨基、羧基和酰胺基 [33] 。以MC-LR为例,MC-LR结构中存在1个可电离的氨基和2个可电离的羧基,pKa分别为2.09,2.19,12.48,随着水体pH从酸性到碱性变化,MC-LR分别以MC-LR-(COOH)2( NH 2 + )、MC-LR-(COO)(COOH)( )、MC-LR-(COO)2( NH 2 + )和MC-LR-(COO)2(NH)形式存在 [34] 。MC-LR的正辛醇/水分配系数(log Dow)与

Figure 1. Molecular structures of microcystins (a) and MC-LR (b)

图1. MCs分子结构(a)及MC-LR分子结构(b)

水体pH呈线性负相关,pH由1增加到10,log Dow由2.18降至−1.76。爆发水华的水体pH普遍大于6.5,此时MC-LR的log Dow约为−0.5,因此生物富集性较低 [34] 。

MC-LR的分子结构同样含有Adda这一特殊的氨基酸结构。然而单独存在的Adda无法表达毒性 [35] ,只有当Adda与六个氨基酸脱水缩合形成七肽单环多肽才具有毒性。Adda自身结构变化也可导致MC-LR毒性改变,当共轭双键由反式(E型)转变为顺式(Z型)时,MC-LR抑制蛋白磷酸酶活性的作用显著减小 [36] 。

4. 微囊藻毒素的毒性机理

人体口服摄入的MCs,少量被胃部吸收,进入小肠后,MCs会侵蚀小肠粘膜上皮细胞和粘膜固有层,大量被小肠粘膜屏障吸收,经血液运输分布全身,同位素示踪显示,70%以上集中在肝脏和肾脏,大部分在两周左右之后,伴随小肠及大肠的杯状细胞分泌粘液通过粪便排遗体外,但仍有少量残留在胃肠黏膜 [37] 。

MCs具有极高细胞选择性和专一生物活性,肝脏是攻击的主要靶器官 [38] 。对大鼠注射或饲喂MCs,解剖观察到实验组的肝脏出现明显充血肿大;进一步的细胞学观察表明,肝细胞内线粒体膨胀,直接导致肝细胞肿大,致使肝细胞间的窦状隙消失,细胞膜上的桥粒和张力丝消失,微丝结构重组 [39] 。MCs进攻肝细胞无法通过自由扩散或渗透等简单的主动运输完成跨膜转移,而需要中间载体参与运输 [10] 。Eriksson等 [40] 认为,存在于肠肝循环系统的胆汁酸(Bile acids)是这类中间载体。MCs主要作用于肝细胞内的蛋白磷酸酶(Protein phosphatases)和环氧化酶(Cyclooxygenase)。由于蛋白磷酸酶1 (PP1)及蛋白磷酸酶2A (PP2A)活性受MCs抑制,而具有相对功能的蛋白激酶(Protein kinase)活性不受影响,细胞内蛋白质被蛋白激酶过磷酸化,并经由细胞信号转导改变其他酶的生物活性,造成肝细胞乃至肝脏的损伤 [41] 。环氧化酶是一类负责催化花生四烯酸(Arachidonic acid)转化为前列腺素(Prostaglandin)的酶 [42] 。MCs能刺激环氧化酶活性,与乙酰辅酶A (Coenzyme A, CoA)上的硫醇基团反应,并且抑制乙酰辅酶A转移酶(acyl-CoA-acyltransferase)和乙酰辅酶A合成酶(acyl-CoA-synthetase)的活性,阻碍花生四烯酸的再吸收,导致前列腺素合成的增加,造成代谢紊乱 [43] 。MCs也能降低肝脏巨噬细胞的吞噬能力,诱使巨噬细胞分泌白细胞介素-1 (Interleukin-1, IL-1),而IL-1与血栓素、前列腺素和肿瘤坏死因子的合成有关 [44] 。

MCs对肾脏也有一定的毒害作用。向大鼠注射MCs能引起尿素和肌酸水平增高,白蛋白的含量则下降;一段时间后,大鼠的尿液出现血红素、蛋白质和胆红素,肾脏乳酸脱氢酶和谷草转氨酶含量减少 [45] 。Milutinović等 [46] 的研究表明,通过对小鼠肾脏注射亚致死剂量的MCs,小鼠的肾小球肿大,内部毛细血管簇破裂;近曲小管和远曲小管管腔膨胀,管壁上皮细胞剥落或丧失。Nobre等 [47] 通过离体肾灌注系统实验,发现MCs可以影响对肾脏灌注压、肾血管阻力和肾小球滤过率。

MCs还可以作用于DNA分子,引起基因突变和癌症的发生。Rao等 [48] 进行了针对藻毒素的遗传毒性研究,对大鼠骨髓嗜热红细胞和大鼠精子进行实验,发现MCs不但阻碍细胞有丝分裂,还能引起DNA分子转移型突变。Lankoff等 [49] 研究发现,MCs通过抑制PP1和PP2A的活性,对细胞MAPK信号通路的负调控有一定作用,令细胞分裂持续不停,使损伤的DNA无法得到及时修复进而演化为不可修复的基因突变,染色体及DNA不断累积的基因突变最终恶化为癌症。

5. 微囊藻毒素的去除方法

MCs的污染问题严重,对人类健康存在巨大危害。目前,处理的主要方法包括物理方法、化学方法、生物方法。

5.1. 物理方法

物理方法去除MCs的核心主要是吸附、吸收及过滤等物理作用。研究最成熟的是活性炭法,此外,二氧化硅、碳纳米管和粘土矿物、离子交换树脂、石英砂和膜滤法等也在蓬勃发展。

活性炭法去除能力较强,费用低廉,被广泛应用 [50] 。常见的活性炭滤料有粉末活性炭和颗粒活性炭。颗粒活性炭比粉末活性炭去除的藻毒素种类更多,两种活性炭的处理MC-LR的极限为0.1 μg/L,更低浓度无法处理 [51] 。Fawell等 [52] 研究发现,20 m/L粉末活性炭和硫酸铁混凝剂共同投入溶液,可以去除85% MCs,增加活性炭投放量,去除率没有显著变化;同样条件下颗粒活性炭处理MC-LR所需的接触时间更长。Pendleton等 [53] 研究多种吸附材料对MCs的吸附能力,发现椰壳质活性炭仅含有微孔,而木基质活性炭既含有微孔还具有中孔,因此木基质活性炭吸附MC-LR的能力更强;吸附能力还受pH影响,在pH为2.5时,木基质活性炭吸附MCs最多。另有研究发现,水中有机质会与MCs竞争吸附于活性炭,造成活性炭处理效率降低 [54] 。尽管活性炭是目前处理MCs应用最多的物理方法,但人们对活性炭解吸MCs还缺乏更深层次的研究,更复杂的生物膜修饰活性炭去除藻毒素的作用和机理还在进一步研究 [55] 。

二氧化硅相比活性炭具有更好的专一性,能够选择性吸附MC-LR和MC-LA等,等温吸附研究发现,二氧化硅对分子量较低的MC-LA吸附倾向性更强 [56] 。二氧化硅的吸附能力受到修饰于外表的各类不同基团影响,自由振动羟基在吸附过程中发挥重要作用 [57] 。碳纳米管和粘土矿物也可用于吸附水中MCs。Morris等 [58] 研究了高岭石(Kaolinite)和蒙脱石(Montmorillonite)两种颗粒性粘土吸附MCs的能力,发现蒙脱石比高岭石去除MCs的能力更强,对初始浓度为4.8 mg/L的MC-LR去除率达到81%。相比粘土矿物,碳纳米管(CNTs)吸附MCs更高效。有研究发现,针对初始浓度为9.5 mg/L的MC-LR,CNTs的吸附量达到6.7 mg/g,是同等条件下高岭土、海泡石、皂石和滑石等粘土矿物吸附能力的5倍,并且CNTs的管外径减少使得比表面积增加,吸附能力随之增加 [59] 。虽然碳纳米管和粘土矿物去除MCs效果良好,由于原料、设备和费用等问题,目前仍无法大规模投入实际应用 [58] 。

离子交换树脂与活性炭配合使用,可以增加过滤水中MCs的效率。Lawton等 [60] 分别比较了三种添加了活性炭的离子交换树脂的去除效率,即阴离子交换树脂、阳离子交换树脂和阴阳离子交换树脂,发现三种离子交换树脂都能部分去除溶解性MCs,但都不能通过单一过滤途径去除所有MCs。而采用单一的石英砂作为滤料,对MCs分子的截留效果并不好,石英砂–活性炭混合滤料过滤水体,再加入明矾作为混凝剂,去除率也只达到50%~60%,因此很难投入实际应用 [61] 。

相较传统工艺,膜滤法是目前最有前景的去除手段。膜技术是利用离子交换膜或有机高分子合成膜的一项综合技术。膜技术包含微滤、超滤、纳滤和反渗透,区别在于膜孔径。孔径在0.1~0.2 μm的称为微滤膜;孔径为0.005 μm的是超滤膜,可以去除分子量1000以上的粒子;纳滤膜能去除分子量大于300的纳米级粒子;而反渗透膜的孔径约为0.3~1.2 nm,能去除分子量200~500的有机物。由于MCs相对分子质量在1000左右,超滤、纳滤和反渗透对其具有不同程度的去除效果,超滤的去除率达到68%,反渗透则高达99.6%,而纳滤近乎可以完全去除水中所有MCs [62] 。膜技术高效安全、无毒副作用,但由于制膜成本昂贵,世界上只有少数水厂使用该技术,美国、法国在部分日处理量1000 m3的水厂已经开始采用膜滤法来处理水体 [63] 。

5.2. 化学方法

化学方法的实质都是氧化反应。大量研究表明,臭氧、氯气、次氯酸钠、紫外光(UV)、UV/TiO2等都可以用来处理MCs,经由强氧化性破坏其结构使其脱毒。

臭氧可以氧化藻毒素分子中Adda上的共轭双键达到降解的目的 [64] 。Rositano等 [65] 向含2.2 mg/LMCs的水体通入臭氧,使水中臭氧浓度达到0.3 mg/L,3 min后检测到MCs消除率高达99%。Hoeger等 [64] 发现臭氧去除MCs的效率与藻细胞密度、臭氧浓度、接触时间和反应温度有关,浓度为1.0 mg/L的臭氧去除藻毒素的量为105 cell/mL,水中臭氧的浓度保持0.05 mg/L以上可完全去除MCs。

氯气和次氯酸钠溶解在水中具有氧化性,对MCs具有一定的去除能力。Nicholso等 [66] 向含有MC-LR的溶液加入氯气或次氯酸钙使次氯酸根达到1 mg/L,30 min后MC-LR降解率高达95%;加入次氯酸钠使溶液次氯酸根达到5 mg/L时,MC-LR的降解率为70%~80%。氯气和次氯酸钠虽然可以去除MCs,但在天然水体中,容易与有机质如富里酸(FA)和腐殖酸(HA)反应生成氯代烃造成二次污染 [67] 。因此,现代水处理更多采用二氧化氯作为净水剂以避免二次污染,但二氧化氯去除MCs的报道很少,反应影响因素和机理也尚未有论文发表。

在光化学处理法中,使用自然光直接降解MCs的效果十分有限,因为太阳的辐射光谱和MCs的最大紫外吸收波长(λ = 238 nm)之间缺乏重叠部分,当水体中存在光敏剂时,MCs的光降解效率将大大提高 [68] 。天然色素可以作为光敏剂加速MC-LR的光降解过程,不同种类和浓度的色素对降解效率的影响有显著差别,当光照充足使,色素参与下可使天然水体中的MC-LR在40天内降解90% [69] 。腐殖质是溶解有机质(Dissolved organicmatter, DOM)的重要成分之一,是另一类存在于自然水体中的光敏剂 [70] 。腐殖质对MC-LR的光降解具有促进作用 [68] ,其原理是MC-LR吸附在腐殖质上(图2),腐殖质吸收了290 nm到可见光波段的太阳光,通过光敏化过程生成活性氧类(Reactive oxygen species, ROS),如羟基自由基、单线态氧或过氧化氢,破坏Adda上的共轭双键使MC-LR脱毒 [71] 。

单波长紫外光降解MCs比自然光降解的效率高,以MC-LR为例,不同紫外波长、不同光照强度下,MC-LR的降解半衰期可以从几分钟到几十分钟,当紫外光波长接近其最大吸收波长238 nm时,MC-LR可以在没有光敏剂的参与下进行光降解 [69] 。在弱紫外光的照射下(0.63 mW/cm2),MCs分子上的Adda共轭双键发生旋转,产生异构体;提高紫外光光照强度和反应温度会提高MCs的光降解速率,而改变水体的pH对光降解的影响较小,酸性条件下降解速率比中性或碱性条件下高 [72] 。也有研究发现,MC-LR在紫外光下的降解效率受光照时间、光照强度和反应温度影响,这与前者的结论一致;254 nm波长,153 μW/cm2紫外光照射初始浓度为84 μg/L的MC-LR,110 min后去除效率高达99%;但是该研究发现,弱酸性和中性(pH 5~7)条件下降解效率最高,而强酸性和强碱性(pH 3或pH 10)条件下降解效率行对更低 [73] ,这与前者的结论不同。

Figure 2. Schematic diagram of possible sorption behavior between DOM and MC-LR

图2. DOM和MC-LR的吸附行为示意图

TiO2光催化法是一类新型的光降解MCs的处理工艺。在紫外光或自然光的照射下,作为催化剂的TiO2在光电效应作用下,表面电子分离产生电子–空穴对,与吸附在催化剂表面的水分子、OH-或O2发生反应,生成活性氧类如∙OH、O2或H2O2,活性氧类进一步将附着在催化剂表面的MCs氧化降解 [74] 。TiO2光催化法降解MCs的影响因素包括MCs初始浓度、TiO2剂量和纯度、光照强度、反应温度和pH等 [75] ,其中pH是最主要的影响因素,因为pH既影响TiO2表面羟基数量,也改变水体中MCs的离子状态,当pH在3~6.4时,TiO2对MCs吸附能力最强,降解效率最高 [76] 。TiO2的剂量和纯度也是提高降解效率的关键因素,P-25钛粉(含80%锐钛型和20%金红石型)被认为降解效率最高,而UV-100 (100%锐钛型)降解效率偏低,通过对TiO2进行掺杂改性,可以拓宽TiO2的吸收光谱,提高其催化能力 [77] 。Liu等 [78] 提出TiO2光催化降解MC-LR的机理是∙OH氧化了MC-LR上的共轭双键,生成二羟基-MC-LR,氧化继续进行导致Adda侧链断裂并将羟基氧化为羧基,生成羧酸-MC-LR。该体系还伴随着副反应的进行,生成了带有完整Adda侧链的MC-LR的肽键水解产物。Antoniou等 [79] 也认为TiO2光催化降解MC-LR是∙OH氧化MC-LR的过程,但与Liu等 [78] 的结果不同的是,∙OH主要进攻MC-LR分子上的苯环、Adda上的共轭双键、甲氧基和肽环上的Mdha氨基酸。

5.3. 生物方法

生物方法处理MCs具有成本低、效率高,较少二次污染等优点。MCs的分子结构稳定,不易被真核生物和大部分细菌的肽酶分解 [80] ,但某些特殊细菌可以改变Adda结构或者打开环肽结构,降解MCs或消除其毒性 [81] 。Jones等 [82] 发现自然水体存在细菌和其他微生物能降解MCs,但作用的过程十分缓慢。Tsuji等 [83] 调查了日本Sagami和Tsukui两个湖在水华爆发后水体内MCs的浓度变化,发现MC-LR和MC-RR浓度在水华爆发14 d内基本稳定,之后开始缓慢降低,在考虑光降解等因素的作用后,据此提出湖水中存在微生物逐步分解这些藻毒素。Cousins等 [84] 在实验室环境内比较了MC-LR在不同水体的浓度变化,结果显示天然水体中MC-LR的浓度在7 d后开始降低,在灭菌的天然水体内MC-LR浓度12 d保持稳定,而在去离子水中27 d以上浓度稳定不变。Takenaka和Watanabe [85] 发现铜绿假单细胞菌能分解MC-LR,从天然水体中筛选分离出该菌株,在50 μg/L初始浓度的MC-LR溶液培养20 d,能使MC-LR降解90%以上。Park等 [86] 从天然水体中分离出一株鞘氨醇单胞菌(Sphingomonas),对MCs具有较高降解能力,人工环境下对MC-LR和MC-RR的最大降解速率达5.4 μg/(L∙d)和13.0 μg/(L∙d)。Jones等 [82] 发现另一种鞘氨醇单胞菌能降低MCs的毒性,原理是使环肽结构变为线性结构,而线性结构的MCs不到原来毒性的0.5%。Bourne等 [87] 研究了鞘氨醇单胞菌对MC-LR的降解机理,提出MC-LR的降解经历了开环变成线性多肽,最终分解为四台化合物,中间产物和最终产物的毒性都显著低于原有毒性。

此外,生物方法还包括生物膜降解法和人工湿地系统等方式。生物膜降解法去除MCs的原理是,将一系列微生物附着在滤膜介质上,使形成的生物膜能够吸附、截留、捕食或消解水藻或者MCs [88] 。Saitou等 [89] 发现生物膜降解能有效去除细胞内MC-LR并且也能降解细胞外溶解的MC-LR。Li等 [90] 调查了日本霞浦湖(Lake Kasumigaura, Japan)净水厂,发现当湖水中营养盐不再增加,生物膜可在7 d后完全去除水体中MC-LR,而当湖水中含P营养盐较多时,完全去除MC-LR需要10 d。Wu等 [91] 提出人工湿地能控制水体的总氮(TN)、总磷水平(TP),降低水华的爆发几率。日本建设省尝试在霞浦湖建设面积达3400 m2的人工湿地以净化湖水,该人工湿地种植了多种水生植物来吸收湖水中过多的N、P营养盐,使湖水营养盐控制在合理水平避免藻华爆发,并且一旦水华发生,这些植物也有吸收MCs的能力。经过五年实验性运行,人工湿地有效调节了水体营养盐,日平均吸收含N盐196 g/(m2∙d),年平均去除40%~50%含P盐;即使有轻微藻华发生,也能日平均去除水藻湿重2.0 kg/d [92] 。

6. 研究展望

尽管目前人们对MCs的来源和致毒机理的研究逐渐加深,并也在去除和控制MCs的技术上取得进展,但仍有巨大的空白值的深入研究。

在MCs的来源和毒理学方面,基因的调控和表达受到环境的影响,但具体是哪些环境因素以及这些环境因素的影响权重,仍然没有研究成果。在初步了解MCs如何攻击人体器官和细胞的背景下,这种毒素具体的作用机制我们也尚不清楚,更无法研究相应的缓解、治疗乃至预防MCs的药物。因此,针对基因的研究和抗毒药物的研发是十分具有前景的。

在MCs的去除方面,已经有学者可以通过环境压力筛选出适应MCs的微生物菌种,并研究可能的降解途径,但是更细致的基因级别的降解机理研究还鲜有报道。复合菌株降解MCs的效率可能大大超过单一菌株,但是具体的菌株组合,还处在摸索阶段。微生物降解MCs仍是一个非常需要探索的领域。

水华是MCs释放的必要条件,水华的预警因此具有重要意义。随着人类工业的继续发展,水体富营养化不可避免还将加重,如何及时搜集水体数据、处理数据并得出结论,对预警水华十分必要。

基金项目

本工作得到了中国海洋大学基本科研业务费(201762030)和液化空气(中国)研发有限公司的研究经费支持。

NOTES

*通讯作者。

文章引用:
钟力, 徐文琦, 胡静文, 张大海. 微囊藻毒素的危害及其分析方法进展[J]. 分析化学进展, 2018, 8(3): 91-102. https://doi.org/10.12677/AAC.2018.83012

参考文献

[1] Matthiensen, A., Beattie, K.A., Yunes, J.S., et al. (2000) [D-Leu1] Microcystin-LR, from the Cyanobacterium Microcystis RST 9501 and from a Microcystis Bloom in the Patos Lagoon Estuary, Brazil. Phytochemistry, 55, 383-387.
https://doi.org/10.1016/S0031-9422(00)00335-6
[2] 王扬才, 陆开宏. 蓝藻水华的危害及治理动态[J]. 水产学杂志, 2004, 17(1): 90-94.
[3] 许川, 舒为群. 微囊藻毒素污染状况、检测及其毒效应[J]. 国外医学: 卫生学分册, 2005, 32(1): 56-60.
[4] Chen, J. and Xie, P. (2007) Microcystin Accumulation in Freshwater Bivalves from Lake Taihu, China, and the Potential Risk to Human Consumption. Environmental Toxicology & Chemistry, 26, 1066-1073.
https://doi.org/10.1897/06-423R1.1
[5] Jiang, Y., Xie, P. and Nie, Y. (2014) Concentration and Bioaccumulation of Cyano-bacterial Bioactive and Odorous Metabolites Occurred in a Large, Shallow Chinese Lake. Bulletin of Environmental Contamination & Toxicology, 93, 643.
https://doi.org/10.1007/s00128-014-1350-2
[6] Wu, S., Wang, S., Yang, H., et al. (2008) Field Studies on the Environmental Factors in Controlling Microcystin Production in the Subtropical Shallow Lakes of the Yangtze River. Bulletin of Environmental Contamination & Toxicology, 80, 329-334.
https://doi.org/10.1007/s00128-008-9378-9
[7] Carmichael, W.W. (1996) Toxic Microcystis and the Environment. Toxic Microcystis.
[8] Orr, P.T. and Jones, G.J. (1998) Relationship between Microcystin Production and Cell Division Rates in Nitrogen-Limited Microcystis aeruginosa Cultures. Limnology & Oceanography, 43, 1604-1614.
https://doi.org/10.4319/lo.1998.43.7.1604
[9] Singh, D.P., Tyagi, M.B., Kumar, A., et al. (2001) Antialgal Activity of a Hepatotoxin-Producing Cyanobacterium, Microcystis aeruginosa. World Journal of Microbiology & Biotechnology, 17, 15-22.
https://doi.org/10.1023/A:1016622414140
[10] Dawson, R.M. (1998) The Toxicology of Microcystins. Toxicon, 36, 953-962.
https://doi.org/10.1016/S0041-0101(97)00102-5
[11] Lindholm, T., Öhman, P., Kurkihelasmo, K., et al. (1999) Toxic Algae and Fish Mortality in a Brackish-Water Lake in Åland, SW Finland. Hydrobiologia, 397, 109-120.
https://doi.org/10.1023/A:1003667728458
[12] Codd, G.A. and Zalewski, M. (2000) Cyanobacterial Toxins, the Perception of Water Quality, and the Prioritization of Eutrophication Control. Ecological Engineering, 16, 51-60.
https://doi.org/10.1016/S0925-8574(00)00089-6
[13] Falconer, I.R., Beresford, A.M. and Runnegar, M.T. (1983) Evidence of Liver Damage by Toxin from a Bloom of the Blue-Green Alga, Microcystis aeruginosa. Medical Journal of Australia, 1, 511.
[14] Howard, A., Mcdonald, A.T., Kneale, P.E., et al. (1996) Cyanobacterial (Blue-Green Algal) Blooms in the UK: A Review of the Current Situation and Potential Management Options. Progress in Physical Geography, 20, 53-61.
https://doi.org/10.1177/030913339602000103
[15] Pouria, S., De, A.A., Barbosa, J., et al. (1998) Fatal Microcystin Intoxication in Haemodialysis Unit in Caruaru, Brazil. Lancet, 352, 21-26.
https://doi.org/10.1016/S0140-6736(97)12285-1
[16] Ueno, Y., Nagata, S., Tsutsumi, T., et al. (1996) Detection of Microcystins, a Blue-Green Algal Hepatotoxin, in Drinking Water Sampled in Haimen and Fusui, Endemic Areas of Primary Liver Cancer in China, by Highly Sensitive Immunoassay. Carcinogenesis, 17, 1317-1321.
https://doi.org/10.1093/carcin/17.6.1317
[17] Yu, S.-Z. (1995) Primary Prevention of Hepatocellular Carcinoma. Journal of Gastroenterology & Hepatology, 10, 674-682.
https://doi.org/10.1111/j.1440-1746.1995.tb01370.x
[18] 中华人民共和国卫生部卫生法制与监督司. 生活饮用水卫生规范[M]. 2001.
[19] 中华人民共和国住房和城乡建设部. 城市供水水质标准(CJ/T206-2005)[M]. 2005.
[20] Kleinkauf, H. and Von Döhren, H. (1996) A Nonribosomal System of Peptide Biosynthesis. Eu-ropean Journal of Biochemistry, 236, 335-351.
https://doi.org/10.1111/j.1432-1033.1996.00335.x
[21] Preece, E.P., Hardy, F.J., Moore, B.C., et al. (2017) A Review of Microcystin Detections in Estuarine and Marine Waters: Environmental Implications and Human Health Risk. Harmful Algae, 61, 31-45.
https://doi.org/10.1016/j.hal.2016.11.006
[22] Humble, A.V., Gadd, G.M. and Codd, G.A. (1997) Binding of Copper and Zinc to Three Cyanobacterial Microcystins Quantified by Differential Pulse Polarography. Water Research, 31, 1679-1686.
https://doi.org/10.1016/S0043-1354(97)00033-X
[23] Utkilen, H. and Gjølme, N. (1995) Iron-Stimulated Toxin Production in Microcystis aeruginosa. Applied & Environmental Microbiology, 61, 797-800.
[24] Dai, R., Liu, H., Qu, J., et al. (2008) Relationship of Energy Charge and Toxin Content of Microcystis aeruginosa in Nitrogen-Limited or Phosphorous-Limited Cultures. Toxicon, 51, 649-658.
https://doi.org/10.1016/j.toxicon.2007.11.021
[25] Gorham, P.R. (1964) Toxic Algae. In: Jackson, D.F., Eds., Algae and Man, Springer, Boston, MA, 307-336.
https://doi.org/10.1007/978-1-4684-1719-7_15
[26] Watanabe, M.F. and Oishi, S. (1985) Effects of Environmental Factors on Toxicity of a Cyanobacterium (Microcystis aeruginosa) under Culture Conditions. Applied & Environmental Microbiology, 49, 1342-1344.
[27] Westhuizen, A.J.V.D. and Eloff, J.N. (1985) Effect of Temperature and Light on the Toxicity and Growth of the Blue-Green Alga Microcystis aeruginosa, (UV-006). Planta, 163, 55-59.
https://doi.org/10.1007/BF00395897
[28] Utkilen, H. and Gjolme, N. (1998) Energy the Dominating Controlling Factor for Microcystin Production in Microcystis aeruginosa. Compilation of Abstracts. 4th International Conference on Toxic Cyanobacteria, No. 63.
[29] Botes, D.P., Wessels, P.L., Kruger, H., et al. (1986) ChemInform Abstract: Structural Studies on Cyanoginosins-LR, -YR, -YA, and -YM, Peptide Toxins from Microcystis aeruginosa. Cheminform, 17, 2747-2748.
https://doi.org/10.1002/chin.198617354
[30] Carmichael, W.W., Beasley, V., Bunner, D.L., et al. (1988) Naming of Cyclic Heptapeptide Toxins of Cyanobacteria (Blue-Green Algae). Toxicon, 26, 971-973.
https://doi.org/10.1016/0041-0101(88)90195-X
[31] Aa, D.L.C., Antoniou, M.G., Hiskia, A., et al. (2011) Can We Effectively Degrade Microcystins?—Implications on Human Health. Anti-Cancer Agents in Medicinal Chemistry, 11, 19-37.
https://doi.org/10.2174/187152011794941217
[32] Rinehart, K.L., Namikoshi, M. and Choi, B.W. (1994) Structure and Bio-synthesis of Toxins from Blue-Green Algae (Cyanobacteria). Journal of Applied Phycology, 6, 159-176.
https://doi.org/10.1007/BF02186070
[33] Rivasseau, C., Martins, S. and Hennion, M.C. (1998) Determination of Some Physi-cochemical Parameters of Microcystins (Cyanobacterial Toxins) and Trace Level Analysis in Environmental Samples Using Liquid Chromatography. Journal of Chromatography A, 799, 155.
https://doi.org/10.1016/S0021-9673(97)01095-9
[34] Maagd, G.J.D., Hendriks, A.J., Seinen, W., et al. (1999) pH-Dependent hydrophobicity of the Cyanobacteria Toxin Microcystin-LR. Water Research, 33, 677-680.
https://doi.org/10.1016/S0043-1354(98)00258-9
[35] Namikoshi, M., Rinehart, K.L., Dahlem, A.M., et al. (1989) Total Synthesis of Adda, the Unique C20, Amino Acid of Cyanobacterial Hepatotoxins. Tetrahedron Letters, 30, 4349-4352.
https://doi.org/10.1016/S0040-4039(00)99357-2
[36] An, J. and Carmichael, W.W. (1994) Use of a Colorimetric Protein Phosphatase Inhibition Assay and Enzyme Linked Immunosorbent Assay for the Study of Microcystins and Nodularins. Toxicon, 32, 1495-1507.
https://doi.org/10.1016/0041-0101(94)90308-5
[37] Ito, E., Harada, K. and Kondo, F. (2000) First Report on the Distribution of Orally Administered Microcystin-LR in Mouse Tissue Using an Immunostaining Method. Toxicon, 38, 37-48.
https://doi.org/10.1016/S0041-0101(99)00084-7
[38] Nishiwaki-Matsushima, R., Ohta, T., Nishiwaki, S., et al. (1992) Liver Tumor Promotion by the Cyanobacterial Cyclic Peptide Toxin Microcystin-LR. Journal of Cancer Research and Clinical Oncology, 118, 420-424.
https://doi.org/10.1007/BF01629424
[39] Miura, G.A., Robinson, N.A., Lawrence, W.B., et al. (1991) Hepatotoxicity of Mi-crocystin-LR in Fed and Fasted Rats. Toxicon, 29, 337-346.
https://doi.org/10.1016/0041-0101(91)90287-2
[40] Eriksson, J.E., Grönberg, L., Nygård, S., et al. (1990) Hepatocellular Uptake of 3H-Dihydromicrocystin-LR, a Cyclic Peptide Toxin. Biochimica et Biophysica Acta, 1025, 60-66.
https://doi.org/10.1016/0005-2736(90)90190-Y
[41] Macías-Silva, M. and García-Sáinz, J.A. (1994) Inhibition of Hormone-Stimulated Inositol Phosphate Production and Disruption of Cytoskeletal Structure. Effects of Okadaic Acid, Microcystin, Chlorpromazine, W7 and Nystatin. Toxicon, 32, 105-112.
https://doi.org/10.1016/0041-0101(94)90026-4
[42] Funk, C.D. (2001) Prostaglandins and Leukotrienes: Advances in Eico-sanoid Biology. Science, 294, 1871-1875.
https://doi.org/10.1126/science.294.5548.1871
[43] Naseem, S.M., Hines, H.B. and Creasia, D.A. (1990) Inhibition of Micro-cystin-Induced Release of Cyclooxygenase Products from Rat Hepatocytes by Anti-Inflammatory Steroids. Proceedings of the Society for Experimental Biology & Medicine Society for Experimental Biology & Medicine, 195, 345-349.
https://doi.org/10.3181/00379727-195-43153
[44] Tracey, K.J., Beutler, B., Lowry, S.F., et al. (1986) Shock and Tissue Injury Induced by Recombinant Human Cachectin. Science, 234, 470-474.
https://doi.org/10.1126/science.3764421
[45] Bhattacharya, R., Sugendran, K., Dangi, R.S., et al. (1997) Toxicity Evaluation of Freshwater Cyanobacterium Microcystis aeruginosa PCC 7806: II. Nephrotoxicity in Rats. Biomedical and Environment Sciences, 10, 93-101.
[46] Milutinović, A., Zivin, M., Zorc-Pleskovic, R., et al. (2003) Nephrotoxic Effects of Chronic Administration of Microcystins-LR and -YR. Toxicon, 42, 281-288.
https://doi.org/10.1016/S0041-0101(03)00143-0
[47] Nobre, A.C.L., Coêlho, G.R., Coutinho, M.C.M., et al. (2001) The Role of Phospholipase A(2) and Cyclooxygenase in Renal Toxicity Induced by Microcystin-LR. Toxicon, 39, 721-724.
https://doi.org/10.1016/S0041-0101(00)00193-8
[48] Rao, P.V. and Bhattacharya, R. (1996) The Cyanobacterial Toxin Mi-crocystin-LR Induced DNA Damage in Mouse Liver in Vivo. Toxicology, 114, 29-36.
https://doi.org/10.1016/S0300-483X(96)03413-0
[49] Lankoff, A., Bialczyk, J., Dziga, D., et al. (2006) The Repair of Gam-ma-Radiation-Induced DNA Damage Is Inhibited by Microcystin-LR, the PP1 and PP2A Phosphatase Inhibitor. Mutagenesis, 21, 83-90.
https://doi.org/10.1093/mutage/gel002
[50] Donati, C., Drikas, M., Hayes, R. and Newcombe, G. (1994) Microcystin-LR Ad-sorption by Powdered Activated Carbon. Water Research, 28, 1735-1742.
https://doi.org/10.1016/0043-1354(94)90245-3
[51] Lahti, K., Rapala, J., Kivimäki, A.L., et al. (2001) Occurrence of Micro-cystins in Raw Water Sources and Treated Drinking Water of Finnish Waterworks. Water Science & Technology, 43, 225-228.
https://doi.org/10.2166/wst.2001.0744
[52] Fawell, J.K., Hart, J., James, H.A., et al. (1993) Blue-Green Algae and Their Tox-ins—Analysis, Toxicity, Treatment and Environmental Control. Water Supply, 11, 109-121.
[53] Pendleton, P., Schumann, R. and Wong, S.H. (2001) Microcystin-LR Adsorption by Activated Carbon. Journal of Colloid and Interface Science, 240, 1-8.
https://doi.org/10.1006/jcis.2001.7616
[54] Pendleton, P., Schumann, R. and Wong, S.H. (2002) Microcystin-RR Adsorption by Activated Carbon. Journal of Colloid and Interface Science, 24, 11-18.
[55] Wang, H., Ho, L., Lewis, D.M., et al. (2007) Dis-criminating and Assessing Adsorption and Biodegradation Removal Mechanisms during Granular Activated Carbon Filtration of Microcystin Toxins. Water Research, 41, 4262-4270.
https://doi.org/10.1016/j.watres.2007.05.057
[56] Ge, S., Liu, W., Lei, G., et al. (2013) In Situ Assembly of Porous Au-Paper Electrode and Functionalization of Magnetic Silica Nanoparticles with HRP via Click Chemistry for Microcystin-LR Immunoassay. Biosensors & Bioelectronics, 49, 111-117.
https://doi.org/10.1016/j.bios.2013.05.010
[57] Iwamoto, M., Hirata, J.I., Matsukami, K. and Kagawa, S. (1983) ChemInform Abstract: Catalytic Oxidation by Oxide Radical Ions. 1. One-Step Hydroxylation of Benzene to Phenol over Group 5 and 6 Oxides Supported on Silica Gel. Chemischer Informationsdienst, 14, 903-905.
https://doi.org/10.1002/chin.198327092
[58] Morris, R.J., Williams, D.E., Luu, H.A., et al. (2000) The Adsorption of Micro-cystin-LR by Natural Clay Particles. Toxicon, 38, 303-308.
https://doi.org/10.1016/S0041-0101(99)00149-X
[59] Sun, X., Guan, L., Shi, H., et al. (2013) Determination of Microcystin-LR with a Glassy Carbon Impedimetric Immunoelectrode Modified with an Ionic Liquid and Multiwalled Carbon Nanotubes. Microchimica Acta, 180, 75-83.
https://doi.org/10.1007/s00604-012-0912-4
[60] Lawton, L.A., Cornish, B.J.P.A. and Macdonald, A.W.R. (1998) Removal of Cyanobacterial Toxins (Microcystins) and Cyanobacterial Cells from Drinking Water Using Domestic Water Filters. Water Research, 32, 633-638.
https://doi.org/10.1016/S0043-1354(97)00267-4
[61] Lambert, T.W., Holmes, C.F.B. and Hrudey, S.E. (1996) Adsorption of Microcystin-LR by Activated Carbon and Removal in Full Scale Water Treatment. Water Research, 30, 1411-1422.
https://doi.org/10.1016/0043-1354(96)00026-7
[62] Neumann, U. and Weckesser, J. (2015) Elimination of Microcystin Peptide Toxins from Water by Reverse Osmosis. Environmental Toxicology, 13, 143-148.
[63] Qu, F., Liang, H., Wang, Z., et al. (2012) Ultrafiltration Membrane Fouling by Extracellular Organic Matters (EOM) of Microcystis aeruginosa in Stationary Phase: Influences of Interfacial Characteristics of Foulants and Fouling Mechanisms. Water Research, 46, 1490-1500.
https://doi.org/10.1016/j.watres.2011.11.051
[64] Hoeger, S.J., Dietrich, D.R. and Hitzfeld, B.C. (2002) Effect of Ozonation on the Removal of Cyanobacterial Toxins during Drinking Water Treatment. Environmental Health Perspectives, 110, 1127-1132.
[65] Rositano, J., Newcombe, G., Nicholson, B. and Sztajnbok, P. (2001) Ozonation of NOM and Algal Toxins in Four Treated Waters. Water Research, 35, 23-32.
https://doi.org/10.1016/S0043-1354(00)00252-9
[66] Nicholson, B.C., Rositano, J. and Burch, M.D. (1994) Destruction of Cyanobacterial Peptide Hepatotoxins by Chlorine and Chloramine. Water Research, 28, 1297-1303.
https://doi.org/10.1016/0043-1354(94)90294-1
[67] Watanabe, M.F., Tsuji, K., Watanabe, Y., et al. (1992) Release of Heptapeptide Toxin (Microcystin) during the Decomposition Process of Microcystis aeruginosa. Natural Toxins, 1, 48-53.
https://doi.org/10.1002/nt.2620010110
[68] Welker, M. and Steinberg, C. (2000) Rates of Humic Substance Photosensitized Degradation of Microcystin-LR in Natural Waters. Environmental Science & Technology, 34, 3415-3419.
https://doi.org/10.1021/es991274t
[69] Tsuji, K., Watanuki, T., Kondo, F., et al. (1996) Stability of Microcystins from Cyano-bacteria. II. Effect of UV Light on Decomposition and Isomerization. Toxicon, 33, 1619-1631.
https://doi.org/10.1016/0041-0101(95)00101-8
[70] Wörmer, L., Huertafontela, M., Cirés, S., et al. (2010) Natural Photodeg-radation of the Cyanobacterial Toxins Microcystin and Cylindrospermopsin. Environmental Science & Technology, 44, 3002-3007.
https://doi.org/10.1021/es9036012
[71] Burns, J.M., Cooper, W.J., Ferry, J.L., et al. (2012) Methods for Reactive Oxygen Species (ROS) Detection in Aqueous Environments. Aquatic Sciences, 74, 683-734.
https://doi.org/10.1007/s00027-012-0251-x
[72] 陈伟, 甘南琴, 宋立荣. 微囊藻毒素在单波长紫外光照射下的光降解动态研究[J]. 化学学报, 2004, 62(2): 142-147.
[73] 李伟英, 许京晶, 张明, 等. 紫外光对微囊藻毒素-LR的去除效果研究[J]. 中国给水排水, 2010, 26(17): 62-65.
[74] Sharma, V.K., Triantis, T.M., Antoniou, M.G., et al. (2012) Destruction of Microcystins by Conventional and Advanced Oxidation Processes: A Review. Separation & Purification Technology, 91, 3-17.
https://doi.org/10.1016/j.seppur.2012.02.018
[75] Lawton, L.A., Robertson, P.K.J., Cornish, B., et al. (1999) Detoxification of Microcystins (Cyanobacterial Hepatotoxins) Using TiO2 Photocatalytic Oxidation. Environmental Science & Technology, 33, 771-775.
https://doi.org/10.1021/es9806682
[76] Antoniou, M.G., Nicolaou, P.A., Shoemaker, J.A., et al. (2009) Impact of the Mor-phological Properties of Thin TiO2 Photocatalytic Films on the Detoxification of Water Contaminated with the Cyanotoxin, Micro-cystin-LR. Applied Catalysis B: Environmental, 91, 165-173.
https://doi.org/10.1016/j.apcatb.2009.05.020
[77] Hamilton, J.W.J., Byrne, J.A., Dunlop, P.S.M., et al. (2014) Evaluating the Mechanism of Visible Light Activity for N,F-TiO2 Using Photoe-lectrochemistry. Journal of Physical Chemistry C, 118, 12206-12215.
https://doi.org/10.1021/jp4120964
[78] Liu, I., Lawton, L.A. and Robertson, P.K.J. (2003) Mechanistic Studies of the Photo-catalytic Oxidation of Microcystin-LR: An Investigation of Byproducts of the Decomposition Process. Environmental Science & Technology, 37, 3214-3219.
https://doi.org/10.1021/es0201855
[79] Antoniou, M.G., Shoemaker, J.A., Aa, D.L.C., et al. (2008) Unveiling New Degradation Intermediates/Pathways from the Photocatalytic Degradation of Microcystin-LR. Environmental Science & Technology, 42, 8877-8883.
https://doi.org/10.1021/es801637z
[80] Tsuji, K., Watanuki, T., Kondo, F., et al. (1997) Stability of Microcystins from Cya-nobacteria—IV. Effect of Chlorination on Decomposition. Toxicon, 35, 1033-1041.
https://doi.org/10.1016/S0041-0101(96)00223-1
[81] Eleuterio, L. and Batista, J.R. (2010) Biodegradation Studies and Se-quencing of Microcystin-LR Degrading Bacteria Isolated from a Drinking Water Biofilter and a Fresh Water Lake. Toxicon, 55, 1434-1442.
https://doi.org/10.1016/j.toxicon.2010.02.020
[82] Jones, G.J., Bourne, D.G., Blakeley, R.L. and Doelle, H. (1994) Degradation of the Cyanobacterial Hepatotoxin Microcystin by Aquatic Bacteria. Natural Toxins, 2, 228-235.
https://doi.org/10.1002/nt.2620020412
[83] Tsuji, K., Setsuda, S., Watanuki, T., et al. (1996) Microcystin Levels during 1992-95 for Lakes Sagami and Tsukui-Japan. Natural Toxins, 4, 189-194.
https://doi.org/10.1002/19960404NT7
[84] Cousins, I.T., Bealing, D.J., James, H.A. and Sutton, A. (1996) Biodegradation of Microcystin-LR by Indigenous Mixed Bacterial Populations. Water Research, 30, 481-485.
https://doi.org/10.1016/0043-1354(95)00189-1
[85] Takenaka, S. and Watanabe, M.F. (1997) Microcystin LR Degradation by Pseudomonas aeruginosa Alkaline Protease. Chemosphere, 34, 749-757.
https://doi.org/10.1016/S0045-6535(97)00002-7
[86] Park, H.D., Sasaki, Y., Maruyama, T., et al. (2001) Degradation of the Cyanobacterial Hepatotoxin Microcystin by a New Bacterium Isolated from a Hypertrophic Lake. Environmental Toxicology, 16, 337-343.
https://doi.org/10.1002/tox.1041
[87] Bourne, D.G., Jones, G.J., Blakeley, R.L., et al. (1996) Enzymatic Pathway for the Bac-terial Degradation of the Cyanobacterial Cyclic Peptide Toxin Microcystin-LR. Applied & Environmental Microbiology, 62, 4086-4094.
[88] Babica, P., Bláha, L. and Maršálek, B. (2004) Removal of Microcystins by Phototrophic Biofilms. A Microcosm Study. Environmental Science and Pollution Research, 12, 369-374.
https://doi.org/10.1065/espr2005.05.259
[89] Saitou, T., Sugiura, N., Itayama, T., Inamori, Y. and Matsumura, M. (2002) Degradation of Microcystin by Biofilm in Practical Treatment Facility. Water Science & Technology, 46, 237-244.
https://doi.org/10.2166/wst.2002.0744
[90] Li, J., Shimizu, K., Maseda, H., et al. (2012) Investigations into the Biodegradation of Microcystin-LR Mediated by the Biofilm in Wintertime from a Biological Treatment Facility in a Drinking-Water Treatment Plant. Bioresource Technology, 106, 27-35.
https://doi.org/10.1016/j.biortech.2011.11.099
[91] Wu, Y., Kerr, P.G., Hu, Z. and Yang, L. (2010) Removal of Cyanobacterial Bloom from a Biopond-Wetland System and the Associated Response of Zoobenthic Diversity. Bioresource Technology, 101, 3903-3908.
https://doi.org/10.1016/j.biortech.2009.12.144
[92] Liu, X., Huang, S., Tang, T. and Liu, X. (2011) Growth Characteristic and Nitrogen Phosphorous Accumulation Ability of Artificial Wetland Plants. Journal of Water Resources & Water Engineering.