-
在厌氧反硝化过程中,细胞内部电子传递主要是由有机物经糖酵解和三羧酸循环产生还原型烟酰胺腺嘌呤二核苷酸(nicotinamide adenine dinucleotide, NADH)为反硝化过程提供电子,电子经复合体Ⅰ(黄素单核苷酸FMN和Fe-S蛋白)传递给醌池,然后一部分电子传递给膜结合的硝酸盐还原酶(NAR)将硝酸盐还原为亚硝酸盐,另一部分电子经复合体Ⅲ传递给周质空间中的细胞色素c,细胞色素c作为电子载体再将电子传递给周质中的亚硝酸盐还原酶(NIR)、一氧化氮还原酶(NOR)和一氧化二氮还原酶(NOS),最终实现将硝酸盐还原为氮气(
$ \mathrm{N}{\mathrm{O}}_{3}^{-}\stackrel{\mathrm{N}\mathrm{A}\mathrm{R}}{\to }\mathrm{N}{\mathrm{O}}_{2}^{-}\stackrel{\mathrm{N}\mathrm{I}\mathrm{R}}{\to } $ NO$ \stackrel{\mathrm{N}\mathrm{O}\mathrm{R}}{\to }{\mathrm{N}}_{2}\mathrm{O}\stackrel{\mathrm{N}\mathrm{O}\mathrm{S}}{\to }{\mathrm{N}}_{2} $ )[1]。生物反硝化过程归根结底是电子的产生与传递,提升电子传递速率是强化反硝化的关键。由于纳米材料独特的物理、化学和电学性质(包括微生物易于粘附和定殖、金属纳米粒子的导电性、比表面积大等),利用纳米材料强化微生物电子传递的研究越来越受关注。在反硝化领域,LIU等[2]综述了零价铁纳米粒子(nZVI)通过生物和非生物协同作用强化反硝化,他们指出虽然nZVI在促进反硝化方面取得了良好的成效,但是,nZVI易产生活性氧物质(ROS),在生物膜表面形成钝化层,限制了nZVI的实际应用。此外,石墨烯[3]、黏土矿物[4]、Mn3O4等[5]在强化生物反硝化过程也发挥了积极的作用。但化学法合成金属纳米粒子的过程需要有毒的化学物质和极端的反应条件,特别是这些金属纳米粒子表面能高,易在水中团聚,进而减少反应的活性位点,降低反应速率。相反,生物法合成纳米颗粒可以在较为温和环境下进行,具有生物相容性、非毒性溶剂和低成本等优点。特别是钯基双金属被报道在选择性催化硝酸盐还原方面表现出较好的对N2的选择性,避免了副产物亚硝酸盐和N2O的过量积累[6]。影响微生物降解污染物的原因除了电子传递效率,还有以群感信号分子为媒介的群体感应(QS)现象,它是微生物通过产生、积累、感应信号分子来调控自身基因表达的一种方式,与生物膜的形成、毒力因子的表达、颗粒污泥的形成和生物酶活性等密切相关。在脱氮方面,目前的研究主要集中于对厌氧氨氧化(Anammox)[7]、异养硝化-好氧反硝化[8]、以及以铜绿假单胞菌为代表的反硝化过程[9],对活性污泥参与的一般厌氧反硝化过程缺乏QS方面的研究。此外,关于纳米粒子对QS的影响目前也只是处于初步研究阶段,例如,LI等[10]研究表明,100 μg·L−1 Ag和氧化石墨烯会显著增加3OC12-HSL信号分子的浓度,促进铜绿假单胞菌(Pseudomonas aeruginosa PAO1)蛋白酶的产生和生物膜的形成,而等量的Fe虽然也刺激了3OC12-HSL的分泌,但并没有导致蛋白酶和生物膜的增加。OUYANG等[11]向恶臭假单胞菌(Pseudomonas putida)生物膜中添加0.5 mg·L−1 ZnO,其促进了QS信号分子c-di-GMP的释放,从而使生物膜有关的基因上调,促进生物膜的形成,而250 mg·L−1 ZnO则表现出相反的抑制作用。
基于上述研究结果,本研究利用取自污水处理厂的活性污泥合成了Bio-Pd0,探究了钯对反硝化酶电子传递的影响,通过三维荧光光谱、生物群落分析和群体感应抑制剂研究了Bio-Pd0对反硝化的影响和群体感应对反硝化效果的调控,本研究结果以期为Bio-Pd0强化反硝化提供参考。
生物钯强化反硝化及群体感应调控
Biosynthetic palladium enhancing denitrification and quorum sensing regulation
-
摘要: 水体氮素污染对生态环境和人类健康具有严重的威胁,因此,探索高效的污水脱氮方法成为水处理领域高度关注的焦点。本研究利用厌氧活性污泥原位合成零价钯(Bio-Pd0),探究了钯负载量对反硝化效果的影响。结果显示,负载适量的钯可以加快反硝化酶对电子的利用速率,从而减少亚硝酸盐和N2O的积累,使硝酸盐的去除率提高了38.54%,而过量的钯负载会抑制生物反硝化效率。从微生物代谢和群体感应两方面进行了机理分析,结果表明,负载适量的钯能够促进微生物的代谢,从而提高对有机物的利用效率。并且添加0.2 g·L−1群感抑制剂(QSI)猪肾酰化酶能进一步强化生物反硝化效果。本研究结果对改善污水脱氮效率具有重要的参考价值。Abstract: Nitrogen pollution in waterbody posed a serious threat to eco-environment and human health. Therefore, to explore efficient denitrification methods has become a focus in the field of water treatment. In this study, zero-valent palladium (Bio-Pd0) was in-situ synthesized by anaerobic sludge, and the effect of palladium loading on denitrification was investigated. The results showed that an appropriate amount of palladium loading could accelerate the electron utilization efficiency, reduce the accumulation of nitrite and N2O, and increase the nitrate removal rate by 38.54%, while denitrification was inhibited with excessive palladium. The mechanism was analyzed from the aspects of microbial metabolism and quorum sensing. The results showed that an appropriate amount of palladium loading could promote the metabolic capacity of microorganisms and increase the organic utilization rate. Moreover, the addition of 0.2 g·L−1 group sensing inhibitor (QSI) porcine kidney acylase could further enhance the biological denitrification effect. The results of this study have an important reference for improving the denitrification effect of sewage.
-
Key words:
- biosynthetic palladium /
- denitrification /
- quorum sensing /
- microbial community structure
-
-
[1] LIU S, WANG C, HOU J, et al. Effects of Ag and Ag2S nanoparticles on denitrification in sediments[J]. Water Research, 2018, 137: 28-36. doi: 10.1016/j.watres.2018.02.067 [2] LIU Y, WANG J. Reduction of nitrate by zero valent iron (ZVI)-based materials: A review[J]. Science of the Total Environment, 2019, 671: 388-403. doi: 10.1016/j.scitotenv.2019.03.317 [3] LI J, PENG Z, HU R, et al. Micro-graphite particles accelerate denitrification in biological treatment systems[J]. Bioresource Technology, 2020, 308: 122935. doi: 10.1016/j.biortech.2020.122935 [4] ZHANG Y, LU C, ChEN Z, et al. Multifaceted synergistic electron transfer mechanism for enhancing denitrification by clay minerals[J]. Science of the Total Environment, 2021, 812: 152222. [5] CHEN X, FENG Q, CAI Q, et al. Mn3O4 nanozyme coating accelerates nitrate reduction and decreases N2O emission during photoelectrotrophic denitrification by thiobacillus denitrificans-CdS[J]. Environmental Science & Technology, 2020, 54(17): 10820-30. [6] BI S, LIU H, ChEN Y, et al. Promoting interspecies hydrogen/electron transfer in Bio-PdNPs-mediated denitrification with the selectivity towards N2[J]. Biochemical Engineering Journal, 2022, 181: 108395. doi: 10.1016/j.bej.2022.108395 [7] 唐鹏. 基于群体感应效应的 Anammox-AGS 工艺特性及调控研究[D]. 青岛: 青岛大学, 2020. [8] 朱子倩. 群体感应系统调控异养硝化好氧反硝化机制研究[D]. 哈尔滨: 哈尔滨工业大学, 2019. [9] ZHAO Z, XIE G, LIU B, et al. A review of quorum sensing improving partial nitritation-anammox process: Functions, mechanisms and prospects[J]. Science of the Total Environment, 2021, 765: 142703. doi: 10.1016/j.scitotenv.2020.142703 [10] LI N, WANG L, YAN H, et al. Effects of low-level engineered nanoparticles on the quorum sensing of Pseudomonas aeruginosa PAO1[J]. Environmental Science and Pollution Research International, 2018, 25(7): 7049-58. doi: 10.1007/s11356-017-0947-5 [11] OUYANG K, MORTIMER M, HOLDEN P A, et al. Towards a better understanding of Pseudomonas putida biofilm formation in the presence of ZnO nanoparticles (NPs): Role of NP concentration[J]. Environment International, 2020, 137: 105485. doi: 10.1016/j.envint.2020.105485 [12] OBEROI A S, HUANG H, KHANNAL S K, et al. Electron distribution in sulfur-driven autotrophic denitrification under different electron donor and acceptor feeding schemes[J]. Chemical Engineering Journal, 2021: 404. [13] LV Y, LI L, CHEN Y, et al. Effects of glucose and biphenyl on aerobic cometabolism of polybrominated diphenyl ethers by Pseudomonas putida: Kinetics and degradation mechanism[J]. International Biodeterior & Biodegrad, 2016, 108: 76-84. [14] 万鹏亮. 某城市污水厂A~2O工艺沿程水质特征分析与提质增效方案研究[D]. 西安: 西安理工大学, 2021. [15] 王共磊. 异养-自养混合式部分ANAMMOX系统同步脱氮除碳效能研究[D]. 太原: 太原理工大学, 2020. [16] SHI H X, WANG J, LIU S Y, et al. New insight into filamentous sludge bulking: Potential role of AHL-mediated quorum sensing in deteriorating sludge floc stability and structure[J]. Water Research, 2022, 212: 118096. doi: 10.1016/j.watres.2022.118096 [17] SHIN H, PARK C, LEE C K, et al. Mitigating biofouling with a vanillin coating on thin film composite reverse osmosis membranes[J]. Environmental Science And Pollution Research, 2020, 27(2): 1677-85. doi: 10.1007/s11356-019-06653-2 [18] CHENG Y, ZHANG Y, SHEN Q, et al. Effects of exogenous short-chain N-acyl homoserine lactone on denitrifying process of Paracoccus denitrificans[J]. Journal of Environmental Science-China, 2017, 54: 33-9. doi: 10.1016/j.jes.2016.05.019 [19] TOYOFUKU M, NOMURA N, FUJII T, et al. Quorum sensing regulates denitrification in Pseudomonas aeruginosa PAO1[J]. Journal of Bacteriology, 2007, 189(13): 4969-72. doi: 10.1128/JB.00289-07 [20] TOYOFUKU M, NOMURA N, KUNO E, et al. Influence of the Pseudomonas quinolone signal on denitrification in Pseudomonas aeruginosa[J]. Journal of Bacteriology, 2008, 190(24): 7947-56. doi: 10.1128/JB.00968-08 [21] LEI X, JIA Y, CHEN Y, et al. Simultaneous nitrification and denitrification without nitrite accumulation by a novel isolated Ochrobactrum anthropic LJ81[J]. Bioresource Technology, 2019: 272. [22] GUO F, LIU H. Impact of heterotrophic denitrification on BOD detection of the nitrate-containing wastewater using microbial fuel cell-based biosensors[J]. Chemical Engineering Journal, 2020: 394. [23] SHI L, ZHANG P, HE Y, et al. Enantioselective effects of cyflumetofen on microbial community and related nitrogen cycle gene function in acid-soil[J]. Science of the Total Environment, 2021, 771: 144831. doi: 10.1016/j.scitotenv.2020.144831 [24] ZHOU C, Ontiveros-Valencia A, Wang Z, et al. Palladium recovery in a H2-based membrane biofilm reactor: Formation of Pd(0) nanoparticles through enzymatic and autocatalytic reductions[J]. Environmental Science & Technology, 2016, 50(5): 2546-55. [25] ZHU X, CAMPANARO S, TREU L, et al. Novel ecological insights and functional roles during anaerobic digestion of saccharides unveiled by genome-centric metagenomics[J]. Water Research, 2019, 151: 271-9. doi: 10.1016/j.watres.2018.12.041 [26] MADDELA N R, SHENG B, YUAN S, et al. Roles of quorum sensing in biological wastewater treatment: A critical review[J]. Chemosphere, 2019, 221: 616-29. doi: 10.1016/j.chemosphere.2019.01.064 [27] MARTINS M L, PINTO U M, RIEDEL K, et al. Quorum sensing and spoilage potential of psychrotrophic enterobacteriaceae isolated from milk J][J]. Biomed Research International, 2018, 2018: 2723157.