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随着社会经济的发展,柴油的使用量增加,但是柴油在生产、运输、装卸、加工及使用过程中的泄露会对土壤环境造成一定的污染,直接或间接地危害人类的生命与健康[1-2]。因此,解决柴油污染土壤问题已成为世界各国所共同面临的问题[3]。
目前,针对柴油污染土壤修复的方法主要包括机械、物理、化学和生物修复方法等[4]。其中,机械、物理、化学修复方法具有费用高、容易产生二次污染等不足[5-7]。而生物修复技术是一种高效、环境友好、低成本的技术,能够将柴油等污染物通过微生物代谢转化成无毒的终产物[8-9],因而被广泛应用于修复柴油污染土壤之中[10]。刘沙沙等[11]已成功利用醋酸钙不动杆菌降解柴油以及污染物,经过62 d的生物修复实验,柴油去除率为69.8%。然而,柴油组成的复杂性决定了其降解需要有不同菌株的参与[12],TAO等[13]研究了土著细菌联合体与外源芽孢杆菌(Bacillus subtilis)共同培养降解原油的实验,细菌群落分析结果表明,在确定的共培养条件下,细菌多样性降低,降解效率提高,同时证明芽孢杆菌对长链烷烃有很好的降解效果。
大量的研究证明,微生物在修复有机物污染土壤的过程中具有良好的应用前景,但目前对于构建微生物菌群的研究较少,本研究从柴油污染土壤中筛选、分离出能够降解柴油污染物的微生物,采用组合实验构建优势菌群,探究了其柴油生物降解特性,研究分析了该菌群中各菌种之间的互作机制,为构建降解柴油的菌群提供参考。
柴油降解菌的筛选、菌群构建及其对柴油和十五烷的降解机理
Screening and community construction of diesel oil degrading bacteria and their degradation mechanism of diesel oil and pentadecane
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摘要: 针对柴油污染土壤生物修复技术效率低的问题,通过构建高效降解菌群修复柴油污染的土壤,采用组合优化和正交实验构建最佳组合与接种比例的菌群,并研究其柴油降解特性。结果表明,通过筛选、鉴定并命名的4株柴油降解菌为Bacillus sp. VOC18-L1、Enterococcus faecalis-L2、Lysinibacillus-L3、Rhodococcus equi-L4;当4株菌接种比例为3∶1∶3∶4,pH = 7.0,30 ℃,转速150 r·min−1时,柴油降解的效果最佳,14 d对7.0 mL·L−1的柴油降解率达到89.0%。通过气相色谱质谱联用仪(GC-MS)检测柴油降解产物,发现该混合菌株能将柴油中的烷烃降解为短链烷烃,最终转化为小分子物质。同时利用KEGG数据库获得代谢丰度图并初步预测每种菌的功能,根据微生物多样性测试结果,进一步证明了混合菌对柴油完全降解的效果优于单种菌种。通过人工构建的微生物菌群可以有效地应用于柴油污染土壤的修复。Abstract: In view of the current low efficiency of bioremediation technology for diesel oil-contaminated soil, a highly efficient flora was constructed to remediate the polluted soil. A combinatorial optimization and orthogonal design were used to construct the flora with the optimal combination and inoculation ratios, and their degradation characteristics of the diesel oil were also studied. The results showed that four diesel degrading bacteria were screened, identified and named as Bacillus sp. VOC18-L1、Enterococcus faecalis-L2、Lysinibacillus-L3、Rhodococcus equi-L4. The optimal degradation efficiency was obtained at their inoculation ratios of 3∶1∶3∶4, pH=7.0, 30 ℃ and the rotational speed of 150 r·min−1. After 14 days of incubation, the degradation efficiency of 7.0 mL·L−1 diesel oil reached 89.0%. The degradation products of diesel oil were detected using GC-MS, which indicated that these mixed strains could first degrade the long-chain alkanes in diesel oil into short-chain alkanes and finally converted them into some small molecular organics. The metabolic abundance maps obtained from KEGG database were used to predict the functions of each strain. According to the results of microbial diversity test, it was further proven that the mixed flora was superior to pure strain in the complete degradation of diesel oil. The artificially optimized and constructed microbial flora could effectively degrade diesel oil in contaminated soil.
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表 1 菌株的菌落形状及柴油降解能力
Table 1. Colony shape and diesel degradability of strains
菌株号 菌落形态 菌体形态 菌落颜色 降解率/% 1# 菌落为扁平、边缘不整齐、表面粗糙皱褶 杆状 白色 27.0 2# 菌落透明、光滑、有光泽 球形 白色 29.0 3# 菌落微黄、表面光滑、边缘整齐 杆状 微黄色 32.0 4# 菌落淡红色、湿润、不规则 杆状 淡红色 35.0 表 2 4种柴油降解菌株的生理生化实验结果
Table 2. Physiological and biochemical characteristics of four diesel degrading bacteria
实验类型 菌株号 1# 2# 3# 4# 淀粉水解实验 − − − − 明胶实验 + − + + 尿素实验 − + − − 甲基红实验 + − + + V-P实验 + − + − 吲哚实验 − − − − 柠檬酸盐实验 − − − − 硫化氢实验 − − − + 触酶实验 − + − + 葡萄糖发酵实验 + − + + 乳糖发酵实验 − − − − 木糖发酵实验 − − − − 麦芽糖发酵实验 + − + + 蔗糖发酵实验 + − − − 注:“+”表示显阳性,“−”表示显阴性。 表 3 菌种组合对柴油降解效率的实验结果
Table 3. Experimental results of degradation efficiency of diesel oil by species strain combination
编号 组合 降解率/% 1 L1+L2 20.9 2 L1+L3 26.2 3 L1+L4 26.1 4 L2+L3 25.8 5 L2+L4 30.9 6 L3+L4 29.3 7 L1+L2+L3 23.5 8 L1+L2+L4 31.5 9 L1+L3+L4 25.0 10 L2+L3+L4 21.1 11 L1+L2+L3+L4 39.6 12 空白 10.9 表 4 4种柴油降解菌的接种比例和对应的柴油降解效率表
Table 4. Inoculation ratio of four diesel oil degrading bacteria and their diesel oil biodegradation efficiency
接种比例
(L1∶L2∶L3∶L4)降解
率/%接种比例
(L1∶L2∶L3∶L4)降解
率/%3∶3∶1∶2 16.5 2∶4∶3∶2 14.8 1∶1∶1∶1 39.3 4∶1∶4∶2 18.5 2∶1∶2∶3 15.3 2∶2∶1∶4 15.7 4∶4∶1∶3 21.4 4∶3∶2∶4 19.1 3∶4∶2∶1 15.6 1∶2∶2∶2 25.5 2∶3∶4∶1 13.7 3∶1∶3∶4 52.5 1∶4∶4∶4 22.3 3∶2∶4∶3 13.2 1∶3∶3∶3 13.1 4∶2∶3∶1 11.7 -
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