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Adekunle A, Ukaigwe S, Bezerra Dos Santos A, Iorhemen OT. Potential for curdlan recovery from aerobic granular sludge wastewater treatment systems - A review. CHEMOSPHERE 2024:142504. [PMID: 38825243 DOI: 10.1016/j.chemosphere.2024.142504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Revised: 05/29/2024] [Accepted: 05/31/2024] [Indexed: 06/04/2024]
Abstract
The aerobic granular sludge (AGS) biotechnology has been explored for wastewater treatment for over two decades. AGS is gaining increased interest due to its enhanced treatment performance ability and the potential for resource recovery from AGS-based wastewater treatment systems. Resource recovery from AGS is a promising approach to sustainable wastewater treatment and attaining a circular economy in the wastewater management industry. Currently, research is at an advanced stage on recovering value-added resources such as phosphorus, polyhydroxyalkanoates, alginate-like exopolysaccharides, and tryptophan from waste aerobic granules. Recently, other value-added resources, including curdlan, have been identified in the aerobic granule matrix, and this may increase the sustainability of biotechnology in the wastewater industry. This paper provides an overview of current AGS biosolids management practices and resource recovery potential. In particular, the potential for enhanced curdlan biosynthesis in the granule matrix and its recovery from AGS wastewater treatment systems is outlined.
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Affiliation(s)
- Adedoyin Adekunle
- School of Engineering, University of Northern British Columbia, 3333 University Way, Prince George, BC, V2N 4Z9, Canada
| | - Sandra Ukaigwe
- Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 2R3, Canada
| | - André Bezerra Dos Santos
- Department of Hydraulic and Environmental Engineering, Federal University of Ceará, Fortaleza, Ceará, Brazil
| | - Oliver Terna Iorhemen
- School of Engineering, University of Northern British Columbia, 3333 University Way, Prince George, BC, V2N 4Z9, Canada.
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2
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Shi H, Mao X, Yang F, Zhu M, Tan N, Tan W, Gu T, Zhang X. Multi-scale analysis of acidophilic microbial consortium biofilm's tolerance of lithium and cobalt ions in bioleaching. JOURNAL OF HAZARDOUS MATERIALS 2024; 474:134764. [PMID: 38824773 DOI: 10.1016/j.jhazmat.2024.134764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 05/15/2024] [Accepted: 05/28/2024] [Indexed: 06/04/2024]
Abstract
Metal ions stress will inhibit the oxidation capacity of iron and sulfur of an acidophilic microbial consortium (AMC), which leads to reduced bioleaching efficiency. This work explored the impacts of Li+ and Co2+ on the composition and function of AMC biofilms with a multi-scale approach. At the reactor scale, the results indicated that the oxidative activity, the adsorption capacity, and the biofilm formation ability of AMC on pyrite surfaces decreased under 500 mM Li+ and 500 mM Co2+. At the biofilm scale, the electrochemical measurements showed that Li+ and Co2+ inhibited the charge transfer between the pyrite working electrode and the biofilm, and decreased the corrosion current density of the pyrite working electrode. At the cell scale, the content of proteins in extracellular polymers substrate (EPS) increased as the concentrations of metal ions increased. Moreover, the adsorption capacity of EPS for Li+ and Co2+ increased. At the microbial consortium scale, a BugBase phenotype analysis showed that under 500 mM Li+ and 500 mM Co2+, the antioxidant stress capacity and the content of mobile gene elements in AMC increased. The results in this work can provide useful data and theoretical support for the regulation strategy of the bioleaching of spent lithium-ion batteries to recover valuable metals.
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Affiliation(s)
- Hongjie Shi
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Xingshun Mao
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Fan Yang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Minglong Zhu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Ningjie Tan
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Wensong Tan
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Tingyue Gu
- Department of Chemical and Biomolecular Engineering, Edison Biotechnology Institute, Ohio University, Athens, OH 45701, USA
| | - Xu Zhang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China.
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Wang P, Yue F, Shao C, Li Q, Shen Y, Xu K, Shi Z, Liu N, Li R, Zhang Z. Bio-sorption capacity of cadmium and zinc by Pseudomonas monteilii with heavy-metal resistance isolated from the compost of pig manure. BIORESOURCE TECHNOLOGY 2024; 399:130589. [PMID: 38490461 DOI: 10.1016/j.biortech.2024.130589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 03/11/2024] [Accepted: 03/12/2024] [Indexed: 03/17/2024]
Abstract
The tolerance of Pseudomonas monteilii X1, isolated from pig manure compost, to Cd and Zn, as well as its capacity for biosorption, were investigated. The minimum inhibitory concentrations (MIC) of Cd and Zn for the strain were 550 mg/L and 800 mg/L, respectively. Untargeted metabolomics analysis revealed that organic acids and derivatives, lipids and lipid-like molecules, and organic heterocyclic compounds were the main metabolites. The glyoxylate and dicarboxylate metabolism pathway were significantly enriched under Cd2+ stress. The isothermal adsorption and adsorption kinetics experiments determined that the strain had adsorption capacities of 9.96 mg/g for Cd2+ and 23.4 mg/g for Zn2+. Active groups, such as hydroxyl, carboxyl, and amino groups on the cell surface, were found to participate in metal adsorption. The strain was able to convert Zn2+ into Zn3(PO4)2·4H2O crystal. Overall, this study suggested that Pseudomonas monteilii has potential as a remediation material for heavy metals.
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Affiliation(s)
- Ping Wang
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| | - Feixue Yue
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| | - Cong Shao
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| | - Qian Li
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| | - Yining Shen
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| | - Kaili Xu
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| | - Zihan Shi
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| | - Naiyu Liu
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| | - Ronghua Li
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, China.
| | - Zengqiang Zhang
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, China; Key Laboratory of Low-carbon Green Agriculture in Northwestern China, Ministry of Agriculture and Rural Affairs, Yangling, Shaanxi 712100, China; Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture and Rural Affairs, Yangling, Shaanxi 712100, China
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Priyadarshanee M, Das S. Spectra metrology for interaction of heavy metals with extracellular polymeric substances (EPS) of Pseudomonas aeruginosa OMCS-1 reveals static quenching and complexation dynamics of EPS with heavy metals. JOURNAL OF HAZARDOUS MATERIALS 2024; 466:133617. [PMID: 38306836 DOI: 10.1016/j.jhazmat.2024.133617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 01/08/2024] [Accepted: 01/23/2024] [Indexed: 02/04/2024]
Abstract
The adsorption behavior and interaction mechanisms of extracellular polymeric substances (EPS) of Pseudomonas aeruginosa OMCS-1 towards chromium (Cr), lead (Pb), and cadmium (Cd) were investigated. EPS-covered (EPS-C) cells exhibited significantly higher (p < 0.0001; two-way ANOVA) removal of Cr (85.58 ± 0.39%), Pb (81.98 ± 1.02%), and Cd (73.88 ± 1%) than EPS-removed (EPS-R) cells. Interactions between EPS-heavy metals were spontaneous (ΔG<0). EPS-Cr(VI) and EPS-Pb(II) binding were exothermic (ΔH<0), while EPS-Cd(II) binding was endothermic (ΔH>0) process. EPS bonded to Pb(II) via inner-sphere complexation by displacement of surrounding water molecules, while EPS-Cr(VI) and EPS-Cd(II) binding occurred through outer-sphere complexation via electrostatic interactions. Increased zeta potential of Cr (29.75%), Pb (41.46%), and Cd (46.83%) treated EPS and unchanged crystallinity (CIXRD=0.13), inferred EPS-metal binding via both electrostatic interactions and complexation mechanism. EPS-metal interaction was predominantly promoted through hydroxyl, amide, carboxyl, and phosphate groups. Metal adsorption deviated EPS protein secondary structures. Strong static quenching mechanism between tryptophan protein-like substances in EPS and heavy metals was evidenced. EPS sequestered heavy metals via complexation with C-O, C-OH, CO/O-C-O, and NH/NH2 groups and ion exchange with -COOH group. This study unveils the fate of Cr, Pb, and Cd on EPS surface and provides insight into the interactions among EPS and metal ions for metal sequestration.
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Affiliation(s)
- Monika Priyadarshanee
- Laboratory of Environmental Microbiology and Ecology (LEnME), Department of Life Science, National Institute of Technology, Rourkela 769 008, Odisha, India
| | - Surajit Das
- Laboratory of Environmental Microbiology and Ecology (LEnME), Department of Life Science, National Institute of Technology, Rourkela 769 008, Odisha, India.
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Li S, Duan G, Xi Y, Chu Y, Li F, Ho SH. Insights into the role of extracellular polymeric substances (EPS) in the spread of antibiotic resistance genes. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 343:123285. [PMID: 38169168 DOI: 10.1016/j.envpol.2023.123285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 11/28/2023] [Accepted: 12/30/2023] [Indexed: 01/05/2024]
Abstract
Antibiotic resistance genes (ARG) are prevalent in aquatic environments. Discharge from wastewater treatment plants is an important point source of ARG release into the environment. It has been reported that biological treatment processes may enhance rather than remove ARG because of their presence in sludge. Attenuation of ARG in biotechnological processes has been studied in depth, showing that many microorganisms can secrete complex extracellular polymeric substances (EPS). These EPS can serve as multifunctional elements of microbial communities, involving aspects, such as protection, structure, recognition, adhesion, and physiology. These aspects can influence the interaction between microbial cells and extracellular ARG, as well as the uptake of extracellular ARG by microbial cells, thus changing the transformative capability of extracellular ARG. However, it remains unclear whether EPS can affect horizontal ARG transfer, which is one of the main processes of ARG dissemination. In light of this knowledge gap, this review provides insight into the role of EPS in the transmission of ARGs; furthermore, the mechanism of ARG spread is analyzed, and the molecular compositions and functional properties of EPS are summarized; also, how EPS influence ARG mitigation is addressed, and factors impacting how EPS facilitate ARG during wastewater treatment are summarized. This review provides comprehensive insights into the role of EPS in controlling the transport and fate of ARG during biodegradation processes at the mechanistic level.
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Affiliation(s)
- Shengnan Li
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, Heilongjiang Province, 150090, China
| | - Guoxiang Duan
- Heilongjiang Academy of Chinese Medical Sciences, Harbin, China
| | - Yucan Xi
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, Heilongjiang Province, 150090, China
| | - Yuhao Chu
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, Heilongjiang Province, 150090, China
| | - Fengxiang Li
- Key Laboratory of Pollution Processes and Environmental Criteria at Ministry of Education, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin, 300350, China
| | - Shih-Hsin Ho
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, Heilongjiang Province, 150090, China.
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Chen DZ, Qiu J, Sun H, Liu Y, Ye J, Chen JM, Lu L. Enhanced chlorobenzene removal by internal magnetic field through initial cell adhesion and biofilm formation. Appl Microbiol Biotechnol 2024; 108:159. [PMID: 38252324 PMCID: PMC10803521 DOI: 10.1007/s00253-024-13001-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Revised: 12/26/2023] [Accepted: 12/30/2023] [Indexed: 01/23/2024]
Abstract
Magnetic fields (MF) have been proven efficient in bioaugmentation, and the internal MFs have become competitive because they require no configuration, despite their application in waste gas treatment remaining largely unexplored. In this study, we firstly developed an intensity-regulable bioaugmentation with internal MF for gaseous chlorobenzene (CB) treatment with modified packing in batch bioreactors, and the elimination capacity increased by up to 26%, surpassing that of the external MF. Additionally, the microbial affinity to CB and the packing surface was enhanced, which was correlated with the ninefold increased secreted ratio of proteins/polysaccharides, 43% promoted cell surface hydrophobicity, and half reduced zeta potential. Furthermore, the dehydrogenase content was promoted over 3 times, and CB removal steadily increased with the rising intensity indicating enhanced biofilm activity and reduced CB bioimpedance; this was further supported by kinetic analysis, which resulted in improved cell adhesive ability and biological utilisation of CB. The results introduced a novel concept of adjustable magnetic bioaugmentation and provided technical support for industrial waste gas treatments. KEY POINTS: • Regulable magnetic bioaugmentation was developed to promote 26% chlorobenzene removal • Chlorobenzene mineralisation was enhanced under the magnetic field • Microbial adhesion was promoted through weakening repulsive forces.
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Affiliation(s)
- Dong-Zhi Chen
- College of Environment, Zhejiang University of Technology, Hangzhou, 310032, China
- School of Petrochemical Engineering and Environment, Zhejiang Ocean University, Zhoushan, 316004, China
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Hangzhou, 310032, China
| | - Jinfeng Qiu
- College of Environment, Zhejiang University of Technology, Hangzhou, 310032, China
- School of Petrochemical Engineering and Environment, Zhejiang Ocean University, Zhoushan, 316004, China
- Zhejiang Provincial Key Laboratory of Petrochemical Pollution Control, Zhoushan, 316004, China
| | - Haimin Sun
- Zhejiang Zhonglan Environmental Technology Co., Ltd., Wenzhou, 325000, China
| | - Yanting Liu
- Yali High School, No. 428 Laodong Western Road, Changsha, Hunan, People's Republic of China, 410007
| | - Jiexu Ye
- College of Environment, Zhejiang University of Technology, Hangzhou, 310032, China
| | - Jian-Meng Chen
- College of Environment, Zhejiang University of Technology, Hangzhou, 310032, China
| | - Lichao Lu
- School of Petrochemical Engineering and Environment, Zhejiang Ocean University, Zhoushan, 316004, China.
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Hangzhou, 310032, China.
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Moghazy RM, Mahmoud RH. Microalgal-based macro-hollow loofah fiber bio-composite for methylene blue removal: A promising step for a green adsorbent. Int J Biol Macromol 2023; 253:127009. [PMID: 37734521 DOI: 10.1016/j.ijbiomac.2023.127009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 09/15/2023] [Accepted: 09/18/2023] [Indexed: 09/23/2023]
Abstract
This study looked into how well the macro-hollow loofah fiber with and without the bio-attaching with green microalga (Chlamydomonas reinhardtii OR242521) was applied methylene blue elimination from water. Based on the results, the biosorption capacity of loofah sponge for methylene blue significantly increased with the increase of contact time, weight of microalgal biofilm, and methylene blue concentration. The maximum biosorption capacity was achieved after 120 min, after 0.042 mgg-1 biofilm weight, and MB concentration of 140 mgL-1. Furthermore, methylene blue's biosorption capacity was strongly affected by pH, reaching its maximum at pH 7. The biosorption capacity of the bio-attached loofah sponge was much higher than that of the loofah sponge, revealing that the microalgae bio-attachment enhanced the biosorption capacity of the loofah sponge. At the end of the MB biosorption process, the used bio-attached loofah sponge can still be utilized once more for the same purpose after the desorption of MB but with a lower biosorption capacity. Furthermore, the loofah sponge could also be applied as a bio-sorbent after domestic use. According to this study, the loofah sponge with or without algal biofilm attachment could be applied as a low-cost efficient bio-sorbent for methylene blue removal from water. However, the loofah sponge's ability for biosorption was dramatically increased by the bio-attachment of microalgae, making it a more potent bio-sorbent. Likewise, this study offers insights into the variables influencing the biosorption capacity of loofah sponges and bio-attached loofah sponges, which could be beneficial for enhancing the biosorption processes.
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Affiliation(s)
- Reda M Moghazy
- Water Pollution Research Department, National Research Centre (NRC), Dokki, Giza 12622, Egypt.
| | - Rehab H Mahmoud
- Water Pollution Research Department, National Research Centre (NRC), Dokki, Giza 12622, Egypt
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Hu F, Wang P, Li Y, Ling J, Ruan Y, Yu J, Zhang L. Bioremediation of environmental organic pollutants by Pseudomonas aeruginosa: Mechanisms, methods and challenges. ENVIRONMENTAL RESEARCH 2023; 239:117211. [PMID: 37778604 DOI: 10.1016/j.envres.2023.117211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Revised: 09/10/2023] [Accepted: 09/25/2023] [Indexed: 10/03/2023]
Abstract
The development of the chemical industry has led to a boom in daily consumption and convenience, but has also led to the release of large amounts of organic pollutants, such as petroleum hydrocarbons, plastics, pesticides, and dyes. These pollutants are often recalcitrant to degradation in the environment, whereby the most problematic compounds may even lead to carcinogenesis, teratogenesis and mutagenesis in animals and humans after accumulation in the food chain. Microbial degradation of organic pollutants is efficient and environmentally friendly, which is why it is considered an ideal method. Numerous studies have shown that Pseudomonas aeruginosa is a powerful platform for the remediation of environmental pollution with organic chemicals due to its diverse metabolic networks and its ability to secrete biosurfactants to make hydrophobic substrates more bioavailable, thereby facilitating degradation. In this paper, the mechanisms and methods of the bioremediation of environmental organic pollutants (EOPs) by P. aeruginosa are reviewed. The challenges of current studies are highlighted, and new strategies for future research are prospected. Metabolic pathways and critical enzymes must be further deciphered, which is significant for the construction of a bioremediation platform based on this powerful organism.
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Affiliation(s)
- Fanghui Hu
- School of Food Science and Pharmaceutical Engineering, Nanjing Normal University, Jiangsu, Nanjing, 210023, China
| | - Panlin Wang
- School of Bioengineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Yunhan Li
- School of Food Science and Pharmaceutical Engineering, Nanjing Normal University, Jiangsu, Nanjing, 210023, China
| | - Jiahuan Ling
- School of Food Science and Pharmaceutical Engineering, Nanjing Normal University, Jiangsu, Nanjing, 210023, China
| | - Yongqiang Ruan
- School of Food Science and Pharmaceutical Engineering, Nanjing Normal University, Jiangsu, Nanjing, 210023, China
| | - Jiaojiao Yu
- School of Medical Imaging, Tianjin Medical University, Tianjin, 300203, China.
| | - Lihui Zhang
- School of Food Science and Pharmaceutical Engineering, Nanjing Normal University, Jiangsu, Nanjing, 210023, China.
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Pagnucco G, Overfield D, Chamlee Y, Shuler C, Kassem A, Opara S, Najaf H, Abbas L, Coutinho O, Fortuna A, Sulaiman F, Farinas J, Schittenhelm R, Catalfano B, Li X, Tiquia-Arashiro SM. Metal tolerance and biosorption capacities of bacterial strains isolated from an urban watershed. Front Microbiol 2023; 14:1278886. [PMID: 37942073 PMCID: PMC10630031 DOI: 10.3389/fmicb.2023.1278886] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 10/10/2023] [Indexed: 11/10/2023] Open
Abstract
Rapid industrialization and urbanization have led to widespread metal contamination in aquatic ecosystems. This study explores the metal tolerance and biosorption characteristics of four bacterial strains (Serratia sp. L2, Raoultella sp. L30, Klebsiella sp. R3, and Klebsiella sp. R19) isolated from Saint Clair River sediments. These strains effectively removed various metal cations (As3+, Pb2+, Cu2+, Mn2+, Zn2+, Cd2+, Cr6+, and Ni2+) in single and multi-metal solutions. Minimum inhibitory concentration (MIC) assays revealed strain-specific variations in metal tolerance, with L2 and L30 exhibiting higher tolerance. Surprisingly, R3 and R19, despite lower tolerance, demonstrated superior metal removal efficiency, challenging the notion that tolerance dictates removal efficacy. In single-metal solutions, R3 and R19 excelled at extracting various metal ions, while competitive binding in multi-metal solutions hindered removal. However, R3 and R19 retained higher removal efficiencies, possibly due to enhanced flocculation activities facilitating metal-ion contact. Comprehensive Fourier-transform infrared (FTIR) analysis highlighted the strains' metal-binding capabilities, with novel peaks emerging after metal exposure, indicative of extracellular polymeric substance (EPS) production. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) confirmed metal accumulation on bacterial surfaces and within cytoplasmic regions and revealed morphological changes and metal adsorption patterns, emphasizing the strains' ability to adapt to metal stress. Scanning transmission microscopy (STEM) and EDX analysis uncovered metal accumulation within bacterial cells, underscoring the complexity of microbial-metal interactions. This study also confirms that the simultaneous presence of an aqueous solution may cause a mutual inhibition in the adsorption of each metal to the EPS resulting in reduced metal uptake, which emphasizes the need to select specific bacterial strains for a given metal-containing effluent. The differences in metal distribution patterns between Klebsiella sp. R19 and Raoultella sp. L30 suggest species-specific metal accumulation strategies driven by environmental conditions and metal availability. The heavy metal-removing capabilities and the ability to grow over a wide range of metal concentrations of the strains used in this study may offer an advantage to employ these organisms for metal remediation in bioreactors or in situ.
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