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Radojević I, Jakovljević V, Grujić S, Ostojić A, Ćirković K. Biofilm formation by selected microbial strains isolated from wastewater and their consortia: mercury resistance and removal potential. Res Microbiol 2024; 175:104092. [PMID: 37331492 DOI: 10.1016/j.resmic.2023.104092] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 05/30/2023] [Accepted: 06/04/2023] [Indexed: 06/20/2023]
Abstract
Wastewater often contains an increased amount of mercury and, at the same time, resistant microorganisms. During wastewater treatment, a biofilm of indigenous microorganisms is often unavoidable. Therefore, the objective of this research is to isolate and identify microorganisms from wastewater and investigate their ability to form biofilms for possible application in mercury removal processes. The resistance of planktonic cells and their biofilms to the effects of mercury was investigated using Minimum Biofilm Eradication Concentration-High Throughput Plates. The formation of biofilms and the degree of resistance to mercury were confirmed in polystyrene microtiter plates with 96 wells. Biofilm on AMB Media carriers (Assisting Moving Bad Media) was quantified using the Bradford protein assay. The removal of mercury ions by biofilms formed on AMB Media carriers of selected isolates and their consortia was determined by a removal test in Erlenmeyer flasks simulating MBBR. All isolates in planktonic form showed some degree of resistance to mercury. The most resistant microorganisms (Enterobacter cloacae, Klebsiella oxytoca, Serratia odorifera, and Saccharomyces cerevisiae) were tested for their ability to form biofilms in the presence and absence of mercury, both in polystyrene plates and on ABM carriers. The results showed that among planktonic forms, K. oxytoca was the most resistant. A biofilm of the same microorganisms was more than 10-fold resistant. Most consortia biofilms had MBEC values > 100,000 μg/mL. Among individual biofilms, E. cloacae showed the highest mercury removal efficiency (97.81% for 10 days). Biofilm consortia composed of three species showed the best ability to remove mercury (96.64%-99.03% for 10 days). This study points to the importance of consortia of different types of wastewater microorganisms in the form of biofilms and suggests that they can be used to remove mercury in wastewater treatment bioreactors.
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Affiliation(s)
- Ivana Radojević
- University of Kragujevac, Faculty of Science, Department of Biology and Ecology, Laboratory of Microbiology, Radoja Domanovića 12, 34000 Kragujevac, Republic of Serbia.
| | - Violeta Jakovljević
- State University of Novi Pazar, Department of Natural-Mathematical Sciences, Vuka Karadžića 9, 36300 Novi Pazar, Republic of Serbia.
| | - Sandra Grujić
- University of Kragujevac, Faculty of Science, Department of Biology and Ecology, Laboratory of Microbiology, Radoja Domanovića 12, 34000 Kragujevac, Republic of Serbia.
| | - Aleksandar Ostojić
- University of Kragujevac, Faculty of Science, Department of Biology and Ecology, Laboratory of Microbiology, Radoja Domanovića 12, 34000 Kragujevac, Republic of Serbia.
| | - Katarina Ćirković
- University of Kragujevac, Faculty of Science, Department of Biology and Ecology, Laboratory of Microbiology, Radoja Domanovića 12, 34000 Kragujevac, Republic of Serbia.
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Zhou X, Lei B, Yin D, Kang J, He Z, He T, Xu X. Application potential of biofertilizer-assisted Pennisetum giganteum in safe utilization of mercury-contaminated paddy fields. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023; 348:119291. [PMID: 37832289 DOI: 10.1016/j.jenvman.2023.119291] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 08/29/2023] [Accepted: 10/06/2023] [Indexed: 10/15/2023]
Abstract
High mercury (Hg) bioaccumulation in crops such as rice in Hg-contaminated areas presents a potential health hazard to humans and wildlife. To develop a safe alternative technique, bacillus-inoculated biofertilizer, citric acid, earthworms, and selenium-modified activated clay were compared for their ability to regulate Hg bioaccumulation in Pennisetum giganteum (P. giganteum). This biofertilizer significantly increased Bacillus sp. abundance in the soil by 157.12%, resulting in the removal of 27.52% of water-soluble Hg fractions through volatilization and adsorption mechanisms. The variation in bioavailable Hg in the soil significantly reduced the total Hg concentration in P. giganteum young leaves, old leaves, stems, and roots of P. giganteum by 74.14%, 48.08%, 93.72%, and 50.91%, respectively (p < 0.05), which is lower than the Chinese feed safety standard (100 ng g-1). The biofertilizer inhibitory potential was highly consistent with that of the selenium-modified activated clay. Biofertilizers significantly reduced the methylmercury concentration in various P. giganteum tissues (p < 0.05), whereas selenium-modified activated clay failed to achieve a comparable effect. This biofertilizer-assisted planting pattern can achieve an economic income quadruple that of the rice planting pattern in the Hg-contaminated paddy fields. Because of its significant environmental and financial applications, the biofertilizer-assisted planting pattern is expected to replace Hg-contaminated paddy fields.
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Affiliation(s)
- Xian Zhou
- Engineering Research Center for Southwest Bio-Pharmaceutical Resources, Key Laboratory of Karst Georesources and Environment, Guizhou Karst Environmental Ecosystems Observation and Research Station, Ministry of Education, Guizhou University, Guiyang, 550025, China; College of Resources and Environment Engineering, Guizhou University, Guiyang, 550025, China
| | - Bangxing Lei
- Engineering Research Center for Southwest Bio-Pharmaceutical Resources, Key Laboratory of Karst Georesources and Environment, Guizhou Karst Environmental Ecosystems Observation and Research Station, Ministry of Education, Guizhou University, Guiyang, 550025, China
| | - Deliang Yin
- Engineering Research Center for Southwest Bio-Pharmaceutical Resources, Key Laboratory of Karst Georesources and Environment, Guizhou Karst Environmental Ecosystems Observation and Research Station, Ministry of Education, Guizhou University, Guiyang, 550025, China; College of Resources and Environment Engineering, Guizhou University, Guiyang, 550025, China.
| | - Jichuan Kang
- Engineering Research Center for Southwest Bio-Pharmaceutical Resources, Key Laboratory of Karst Georesources and Environment, Guizhou Karst Environmental Ecosystems Observation and Research Station, Ministry of Education, Guizhou University, Guiyang, 550025, China.
| | - Zhangjiang He
- Engineering Research Center for Southwest Bio-Pharmaceutical Resources, Key Laboratory of Karst Georesources and Environment, Guizhou Karst Environmental Ecosystems Observation and Research Station, Ministry of Education, Guizhou University, Guiyang, 550025, China
| | - Tianrong He
- Engineering Research Center for Southwest Bio-Pharmaceutical Resources, Key Laboratory of Karst Georesources and Environment, Guizhou Karst Environmental Ecosystems Observation and Research Station, Ministry of Education, Guizhou University, Guiyang, 550025, China
| | - Xiaohang Xu
- Engineering Research Center for Southwest Bio-Pharmaceutical Resources, Key Laboratory of Karst Georesources and Environment, Guizhou Karst Environmental Ecosystems Observation and Research Station, Ministry of Education, Guizhou University, Guiyang, 550025, China
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Nivetha N, Srivarshine B, Sowmya B, Rajendiran M, Saravanan P, Rajeshkannan R, Rajasimman M, Pham THT, Shanmugam V, Dragoi EN. A comprehensive review on bio-stimulation and bio-enhancement towards remediation of heavy metals degeneration. CHEMOSPHERE 2023; 312:137099. [PMID: 36372332 DOI: 10.1016/j.chemosphere.2022.137099] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 10/20/2022] [Accepted: 10/30/2022] [Indexed: 06/16/2023]
Abstract
Pollution of heavy metals is one of the risky contaminations that should be managed for all intents and purposes of general well-being concerns. The bioaccumulation of these heavy metals inside our bodies and pecking orders will influence our people in the future. Bioremediation is a bio-mechanism where residing organic entities use and reuse the squanders that are reused to one more form. This could be accomplished by taking advantage of the property of explicit biomolecules or biomass that is equipped for restricting by concentrating the necessary heavy metal particles. The microorganisms can't obliterate the metal yet can change it into a less harmful substance. In this unique circumstance, this review talks about the sources, poisonousness, impacts, and bioremediation strategies of five heavy metals: lead, mercury, arsenic, chromium, and manganese. The concentrations here are the ordinary strategies for bioremediation such as biosorption methods, the use of microbes, green growth, and organisms, etc. This review demonstrates the toxicity of heavy metal contamination degradation by biotransformation through bacterioremediation and biodegradation through mycoremediation.
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Affiliation(s)
- N Nivetha
- School of Bio-Sciences and Technology, Vellore Institute of Technology, Vellore, 632014, Tamil Nadu, India
| | - B Srivarshine
- School of Bio-Sciences and Technology, Vellore Institute of Technology, Vellore, 632014, Tamil Nadu, India
| | - B Sowmya
- School of Bio-Sciences and Technology, Vellore Institute of Technology, Vellore, 632014, Tamil Nadu, India
| | | | - Panchamoorthy Saravanan
- Department of Petrochemical Technology, UCE - BIT Campus, Anna University, Tiruchirappalli, Tamil Nadu, India
| | - R Rajeshkannan
- Department of Chemical Engineering, Annamalai University, Tamilnadu, India
| | - M Rajasimman
- Department of Chemical Engineering, Annamalai University, Tamilnadu, India
| | - Thi Hong Trang Pham
- Institute for Global Health Innovations, Duy Tan University, Da Nang, 550000, Viet Nam; Faculty of Natural Science, Duy Tan University, Da Nang, 550000, Viet Nam
| | - VenkatKumar Shanmugam
- School of Bio-Sciences and Technology, Vellore Institute of Technology, Vellore, 632014, Tamil Nadu, India.
| | - Elena-Niculina Dragoi
- "Cristofor Simionescu" Faculty of Chemical Engineering and Environmental Protection, "Gheorghe Asachi" Technical University, Iasi, Bld Mangeron No 73, 700050, Romania
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Recent developments in environmental mercury bioremediation and its toxicity: A review. ACTA ACUST UNITED AC 2020. [DOI: 10.1016/j.enmm.2020.100283] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Mariano C, Mello IS, Barros BM, da Silva GF, Terezo AJ, Soares MA. Mercury alters the rhizobacterial community in Brazilian wetlands and it can be bioremediated by the plant-bacteria association. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2020; 27:13550-13564. [PMID: 32030584 DOI: 10.1007/s11356-020-07913-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 01/28/2020] [Indexed: 06/10/2023]
Abstract
This study examined how soil mercury contamination affected the structure and functionality of rhizobacteria communities from Aeschynomene fluminensis and Polygonum acuminatum and how rhizobacteria mediate metal bioremediation. The strains were isolated using culture-dependent methods, identified through 16S rDNA gene sequencing, and characterized with respect to their functional traits related to plant growth promotion and resistance to metals and antibiotics. The bioremediation capacity of the rhizobacteria was determined in greenhouse using corn plants. The isolated bacteria belonged to the phyla Actinobacteria, Deinococcus-Thermus, Firmicutes, and Proteobacteria, with great abundance of the species Microbacterium trichothecenolyticum. The rhizobacteria abundance, richness, and diversity were greater in mercury-contaminated soils. Bacteria isolated from contaminated environments had higher minimum inhibitory concentration values, presented plasmids and the merA gene, and were multi-resistant to metals and antibiotics. Enterobacter sp._C35 and M. trichothecenolyticum_C34 significantly improved (Dunnett's test, p < 0.05) corn plant growth in mercury-contaminated soil. These bacteria helped to reduce up to 87% of the mercury content in the soil, and increased the mercury bioaccumulation factor by up to 94%. Mercury bioremediation mitigated toxicity of the contaminated substrate. Enterobacter sp._C35, Bacillus megaterium_C28, and Bacillus mycoides_C1 stimulated corn plant growth and could be added to biofertilizers produced in research and related industries.
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Affiliation(s)
- Caylla Mariano
- Laboratory of Biotechnology and Microbial Ecology, Institute of Biosciences, Federal University of Mato Grosso, Cuiabá, Mato Grosso, Brazil
| | - Ivani Souza Mello
- Laboratory of Biotechnology and Microbial Ecology, Institute of Biosciences, Federal University of Mato Grosso, Cuiabá, Mato Grosso, Brazil
| | - Breno Martins Barros
- Laboratory of Biotechnology and Microbial Ecology, Institute of Biosciences, Federal University of Mato Grosso, Cuiabá, Mato Grosso, Brazil
| | | | - Ailton Jose Terezo
- Central Analytical of Fuels, Department of Chemistry, Federal University of Mato Grosso, Cuiabá, Mato Grosso, Brazil
| | - Marcos Antônio Soares
- Laboratory of Biotechnology and Microbial Ecology, Institute of Biosciences, Federal University of Mato Grosso, Cuiabá, Mato Grosso, Brazil.
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Rivas-Castillo AM, Guatemala-Cisneros ME, Gómez-Ramírez M, Rojas-Avelizapa NG. Metal removal and morphological changes of B. megaterium in the presence of a spent catalyst. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART A, TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING 2019; 54:533-540. [PMID: 30755080 DOI: 10.1080/10934529.2019.1571307] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 12/25/2018] [Accepted: 01/05/2019] [Indexed: 06/09/2023]
Abstract
Spent catalysts represent an environmental concern, mainly due to their elevated metal content. Although conventional treatment methods for spent catalysts are available, they generate large volumes of potentially harmful wastes and gaseous emissions. To overcome the environmental impact, biotechnological approaches are currently being explored and developed. Thus, the current study assayed the capability of Bacillus megaterium strain MNSH1-9K-1 to remove Al, Ni, V and Ti contained in the spent catalyst coded as ECAT-TL-II. To this end, B. megaterium MNSH1-9K-1 growth and metal uptake abilities in the presence of ECAT-TL-II spent catalyst at 15% (wt/vol) pulp density were evaluated in modified Starkey medium at 37 °C and 200 rpm. The results presented here show B. megaterium resistance capability to the high-metal content residue, and its Al, V and Ni removal ability, in 1,059.15 ± 197.28 mg kg-1 of Al, 43.39 ± 24.13 mg kg-1 of V and 0.58 ± 0.00 mg kg-1 of Ni, corresponding to the 0.79%, 1.63% and 0.46% of each metal content, respectively, while no Ti removal was detected. Besides, it was observed that the sporulation process took place in B. megaterium cells in the presence of the spent catalyst. The results shown in this study suggest the potential of the strain MNSH1-9K-1 for the removal of metals contained in high-metal content residues, contributing also to the knowledge of the metal resistance and removal abilities of B. megaterium in the presence of a spent catalyst, and how morphological cell changes may be occurring while metal removal is taking place.
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Affiliation(s)
- Andrea M Rivas-Castillo
- a Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada del IPN , Querétaro , México
- b Universidad Tecnológica de Zona Metropolitana del Valle de México , Tizayuca , México
| | | | - Marlenne Gómez-Ramírez
- a Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada del IPN , Querétaro , México
| | - Norma G Rojas-Avelizapa
- a Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada del IPN , Querétaro , México
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Chen J, Dong J, Chang J, Guo T, Yang Q, Jia W, Shen S. Characterization of an Hg(II)-volatilizing Pseudomonas sp. strain, DC-B1, and its potential for soil remediation when combined with biochar amendment. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2018; 163:172-179. [PMID: 30053587 DOI: 10.1016/j.ecoenv.2018.07.071] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 07/12/2018] [Accepted: 07/19/2018] [Indexed: 06/08/2023]
Abstract
Hg contamination is a critical environmental problem, and its remediation using cost-effective and environmentally friendly methods is highly desirable. In this study, a multi-metal-resistant bacterium showing strong Hg(II) volatilization ability, Pseudomonas sp. DC-B1, was isolated from heavy metal-contaminated soils. DC-B1 volatilized 81.1%, 79.2% and 74.3% of the initial Hg2+ from culture solutions with initial Hg2+ concentrations of 5.1, 10.4, and 15.7 mg/L, respectively, within 24 h. Microcosm experiments were performed to investigate the remediation of Hg(II)-spiked soils inoculated with DC-B1 coupled with sawdust biochar amendment. The efficiency of Hg removal from two types of soil samples with different properties and an initial Hg(II) content of approximately 100 mg/kg was enhanced 5.7-13.1% by bio-augmentation with inoculation of the bacterial strain DC-B1, 5.4-10.7% by amendment of 4% (w/w) biochar, and 10.7-23.2% by the combination of DC-B1 and biochar amendments over an incubation period of 24 d over the efficiency in the control treatment under flooded conditions. Longer root lengths were observed in lettuce grown in the treated soils than in lettuce from the control soil, confirming the bioremediation efficacy of the two bioagents for soil Hg contamination.
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Affiliation(s)
- Jinquan Chen
- School of Ecology and Environmental Science & Yunnan Key Laboratory for Plateau Mountain Ecology and Restoration of Degraded Environments, Yunnan University, Kunming 650091, China
| | - Jia Dong
- School of Ecology and Environmental Science & Yunnan Key Laboratory for Plateau Mountain Ecology and Restoration of Degraded Environments, Yunnan University, Kunming 650091, China
| | - Junjun Chang
- School of Ecology and Environmental Science & Yunnan Key Laboratory for Plateau Mountain Ecology and Restoration of Degraded Environments, Yunnan University, Kunming 650091, China.
| | - Tongtong Guo
- Institute of International Rivers and Eco-security, Yunnan University, Kunming, Yunnan 650091, China
| | - Qingchen Yang
- Institute of International Rivers and Eco-security, Yunnan University, Kunming, Yunnan 650091, China
| | - Wei Jia
- School of Architecture and Planning, Yunnan University, Kunming 650091, China
| | - Shili Shen
- School of Ecology and Environmental Science & Yunnan Key Laboratory for Plateau Mountain Ecology and Restoration of Degraded Environments, Yunnan University, Kunming 650091, China.
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Diverse molecular resistance mechanisms of Bacillus megaterium during metal removal present in a spent catalyst. BIOTECHNOL BIOPROC E 2017. [DOI: 10.1007/s12257-016-0019-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Mahbub KR, Bahar MM, Labbate M, Krishnan K, Andrews S, Naidu R, Megharaj M. Bioremediation of mercury: not properly exploited in contaminated soils! Appl Microbiol Biotechnol 2017; 101:963-976. [DOI: 10.1007/s00253-016-8079-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 12/14/2016] [Indexed: 12/18/2022]
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Mahbub KR, Krishnan K, Megharaj M, Naidu R. Bioremediation potential of a highly mercury resistant bacterial strain Sphingobium SA2 isolated from contaminated soil. CHEMOSPHERE 2016; 144:330-337. [PMID: 26378869 DOI: 10.1016/j.chemosphere.2015.08.061] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2015] [Revised: 07/29/2015] [Accepted: 08/19/2015] [Indexed: 06/05/2023]
Abstract
A mercury resistant bacterial strain, SA2, was isolated from soil contaminated with mercury. The 16S rRNA gene sequence of this isolate showed 99% sequence similarity to the genera Sphingobium and Sphingomonas of α-proteobacteria group. However, the isolate formed a distinct phyletic line with the genus Sphingobium suggesting the strain belongs to Sphingobium sp. Toxicity studies indicated resistance to high levels of mercury with estimated EC50 values 4.5 mg L(-1) and 44.15 mg L(-1) and MIC values 5.1 mg L(-1) and 48.48 mg L(-1) in minimal and rich media, respectively. The strain SA2 was able to volatilize mercury by producing mercuric reductase enzyme which makes it potential candidate for remediating mercury. ICP-QQQ-MS analysis of Hg supplemented culture solutions confirmed that almost 79% mercury in the culture suspension was volatilized in 6 h. A very small amount of mercury was observed to accumulate in cell pellets which was also evident according to ESEM-EDX analysis. The mercuric reductase gene merA was amplified and sequenced. The deduced amino acid sequence demonstrated sequence homology with α-proteobacteria and Ascomycota group.
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Affiliation(s)
- Khandaker Rayhan Mahbub
- Centre for Environmental Risk Assessment and Remediation, The University of South Australia, Mawson Lakes, Adelaide, SA 5095, Australia; Global Centre for Environmental Remediation, Faculty of Science and Information Technology, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), The University of Newcastle, Callaghan, NSW 2308, Australia.
| | - Kannan Krishnan
- Global Centre for Environmental Remediation, Faculty of Science and Information Technology, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), The University of Newcastle, Callaghan, NSW 2308, Australia.
| | - Mallavarapu Megharaj
- Centre for Environmental Risk Assessment and Remediation, The University of South Australia, Mawson Lakes, Adelaide, SA 5095, Australia; Global Centre for Environmental Remediation, Faculty of Science and Information Technology, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), The University of Newcastle, Callaghan, NSW 2308, Australia.
| | - Ravi Naidu
- Centre for Environmental Risk Assessment and Remediation, The University of South Australia, Mawson Lakes, Adelaide, SA 5095, Australia; Global Centre for Environmental Remediation, Faculty of Science and Information Technology, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), The University of Newcastle, Callaghan, NSW 2308, Australia.
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Singh VK, Singh NA, Kumar N, Raghu HV, Sharma PK, Singh KP, Yadav A. Spore immobilization and its analytical performance for monitoring of aflatoxin M1 in milk. Can J Microbiol 2014; 60:793-8. [PMID: 25387994 DOI: 10.1139/cjm-2014-0465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Immobilization of Bacillus megaterium spores on Eppendorf tubes through physical adsorption has been used in the detection of aflatoxin M1 (AFM1) in milk within real time of 45 ± 5 min using visual observation of changes in a chromogenic substrate. The appearance of a sky-blue colour indicates the absence of AFM1 in milk, whereas no colour change indicates the presence of AFM1 in milk at a 0.5 ppb Codex maximum residue limit. The working performance of the immobilized spores was shown to persist for up to 6 months. Further, spores immobilized on 96-well black microtitre plates by physical adsorption and by entrapment on sensor disk showed a reduction in detection sensitivity to 0.25 ppb within a time period of 20 ± 5 min by measuring fluorescence using a microbiological plate reader through the addition of milk and fluorogenic substrate. A high fluorescence ratio indicated more substrate hydrolysis due to spore-germination-mediated release of marker enzymes of spores in the absence of AFM1 in milk; however, low fluorescence ratios indicated the presence of AFM1 at 0.25 ppb. Immobilized spores on 96-well microtitre plates and sensor disks have shown better reproducibility after storage at 4 °C for 6 months. Chromogenic assay showed 1.38% false-negative and 2.77% false-positive results while fluorogenic assay showed 4.16% false-positive and 2.77% false-negative results when analysed for AFM1 using 72 milk samples containing raw, pasteurized, and dried milk. Immobilization of spores makes these chromogenic and fluorogenic assays portable, selective, cost-effective for real-time detection of AFM1 in milk at the dairy farm, reception dock, and manufacturing units of the dairy industry.
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Affiliation(s)
- V K Singh
- a Microbial Biosensors and Food Safety Laboratory, Dairy Microbiology Division, National Dairy Research Institute, Indian Council of Agricultural Research, Karnal 132001, Haryana, India
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