Bacterial Immobilization Research Articles

Mechanistic studies on bioremediation of dye using Aeromonas veronii immobilized peanut shell biochar

Recalcitrant chemicals in the environment not only present obstacles to living organisms but also contribute to the degradation of natural resources. One contribution to environmental pollution is the discharge of synthetic dyes from the textile sector. This study investigates the combined effect of microbial cells and biochar on eliminating methyl orange (MO) dye. The immobilization of Aeromonas veronii on peanut shell biochar (APSB) was conducted to investigate its efficacy in removing MO dye from water. PSB synthesized by pyrolysis at 300 °C for 120 min showed maximum bacterial immobilization potential. The highest degradation rate of 96.19 % was achieved in APSB within 96 h using MO dye concentration of 100 mg L−1, incubation temperature of 37 °C, pH 7, and biocatalyst dosage of 1g L−1. In comparison, free cells achieved degradation rates of 72.53 % and 61.56 % for PSB. Moreover, the adsorption process was primarily controlled by PSB, with subsequent dye mineralization by A. veronii, as supported by FTIR and LC-MS studies. Moreover, this innovative approach exhibited the reusability of the biocatalyst, giving 76.23 % removal after fifth cycle, suggesting sustainable alternative in dye remediation and potential option for real-time applications.

Effect of electroinductive conditions on biofilm production capacity of some industrially important bacteria

Biofilms are intricate microbial deposits on biotic and abiotic surfaces, with significant medical and biotechnological implications. This study explored biofilm formation by Acetobacter aceti ATCC15973, Pseudomonas aeruginosa ATCC9027, Serratia marcescens ATCC14756, Gluconobacter oxydans ATCC19357, Rhodobacter sphaeroides ATCC17023, and Bacillus subtilis ATCC6633 on wood, glass, steel, PVC, and PET surfaces using qualitative methods. Effects of electrical stimulation (6V, 4.5A), magnetic fields (1000 G), and electromagnetic flux (5 mT) on biofilm formation were assessed via Crystal Violet Binding Assay. G. oxydans ATCC19357 exhibited highest adherence on PVC and wood (2.0145 and 2.402 log cfu/ml, respectively) under electrical stimulation. A. aceti ATCC15973 showed highest adherence on steel, PET, and glass (1.944, 0.9005, and 0.876 log cfu/ml). R. sphaeroides ATCC17023 demonstrated highest adherence on PVC, steel, PET, and glass (1.0895 to 1.7495 log cfu/ml) under magnetic induction; B. subtilis ATCC6633 had highest wood adherence (1.491 log cfu/ml). G. oxydans ATCC19357 showed highest overall adhesion with electromagnetic induction. PVC supported highest biofilm growth (39 %). Biophysical factors varied in enhancing biofilm formation, suggesting potential for bacterial immobilization technologies in bioremediation and industrial fermentation

Development of Technology for the Bioleaching of Uranium in a Solution of Bacterial Immobilization

This study presents findings regarding the kinetics of ferrous iron oxidation in solution mediated by Acidithiobacillus ferrooxidans bacteria within a continuous-flow bioreactor employing diverse types of immobilizers. The objective is to augment the rate of ferrous iron oxidation in solutions utilizing an immobilizer for Acidithiobacillus ferrooxidans strains. Immobilization represents a promising avenue for enhancing the efficiency of Fe2⁺ oxidation via acidophilic ferrooxidizing bacteria, leading to a several-fold increase in oxidation rate. A comparative analysis was conducted to evaluate the efficacy of different types of immobilizer in facilitating iron oxidation within a continuous-flow bioreactor, including the application of wood chips coated with Fe(OH)3. The results indicate that wood chips coated with iron hydroxide serve as effective type of immobilizer, facilitating the robust attachment of Acidithiobacillus ferrooxidans via electrostatic interactions between negatively charged bacteria and positively charged surfaces. Experimental investigations were conducted using novel immobilization matrices in pilot-scale tests simulating the underground borehole leaching (UBL) of uranium. The bioactivation of leaching solutions enhances the efficiency and environmental compatibility of UBL compared to conventional chemical oxidation methods. The relationships between redox potential and ferric iron content in bioactivated solutions during the UBL of uranium were delineated. The significance of this study lies in its elucidating the pivotal role of Fe2⁺ oxidation in uranium extraction processes, particularly in the context of UBL. By employing bioactivation mediated by Acidithiobacillus ferrooxidans, the study demonstrates not only enhanced uranium extraction efficiency, but also markedly improved environmental sustainability compared to traditional chemical oxidation methods. The findings reveal crucial correlations between redox potential and ferric iron concentration in bioactivated solutions.

Enhancing microbial fuel cell performance through microbial immobilization.

Bio-electrochemical Systems (BES), particularly Microbial Fuel Cells (MFC), have emerged as promising technologies in environmental biotechnology. This study focused on optimizing the anode bacterial culture immobilization process to enhance BES performance. The investigation combines and modifies two key immobilization methods: covalent bonding with glutaraldehyde and inclusion in a chitosan gel in order to meet the criteria andrequirements of the bio-anodes in MFC. The performance of MFCs with immobilized and suspended cultures was compared in parallel experiments. Both types showed similar substrate utilization dynamics with slight advantage of the immobilized bio-anode considering thelowerconcentration of biomass. The immobilized MFC exhibited higher power generation and metabolic activity, as well. Probably, this is due to improved anodic respiration and higher coulombic efficiency of the reactor. Analysis of organic acids content supported this conclusion showing significant inhibition of the fermentation products production in the MFC reactor with immobilized anode culture.

β-tricalcium phosphate enhanced biomineralization of Cd2+ and Pb2+ by Sporosarcina ureilytica HJ1 and Sporosarcina pasteurii HJ2

Microbiologically induced CaCO3 precipitation (MICP) has been proposed as a potential bioremediation method to immobilize contaminating metals. In this study, carbonate mineralizing bacteria HJ1 and HJ2, isolated from heavy metal contaminated soil, was employed for Cd2+ and Pb2+ immobilization with or without β-tricalcium phosphate addition. Compared with the only treatments amended with strains, the combined application of β-tricalcium phosphate and HJ1 improved the immobilization rates of Cd and Pb by 1.49 and 1.70 times at 24 h, and the combined application of β-tricalcium phosphate and HJ2 increased the immobilization rates of Cd and Pb by 1.25 and 1.79 times. The characterization of biomineralization products revealed that Cd2+ and Pb2+ primarily immobilized from the liquid phase as CdCO3 and PbCO3, and the addition of β-tricalcium phosphate facilitated the formation of Ca4.03Cd0.97(PO4)3(OH) and Pb3(PO4)2. Also, the calcium source was related to the speciation of carbonate precipitation and improved the Cd and Pb remediation efficiency. This research demonstrated the feasibility and effectiveness of MICP combined with β-tricalcium phosphate in immobilization of Cd and Pb, which will provide a fundamental basis for future applications of MICP to mitigate soil heavy metal pollutions.

Effect of the Application of Ochrobactrum sp.-Immobilised Biochar on the Remediation of Diesel-Contaminated Soil.

The immobilisation of bacteria on biochar has shown potential for enhanced remediation of petroleum hydrocarbon-contaminated soil. However, there is a lack of knowledge regarding the effect of bacterial immobilisation on biosolids-derived biochar for the remediation of diesel-contaminated soil. This current study aimed to assess the impact of the immobilisation of an autochthonous hydrocarbonoclastic bacteria, Ochrobacterium sp. (BIB) on biosolids-derived biochar for the remediation of diesel-contaminated soil. Additionally, the effect of fertiliser application on the efficacy of the BIB treatment was investigated. Biochar (BC) application alone led to significantly higher hydrocarbon removal than the control treatment at all sampling times (4887-11,589 mg/kg higher). When Ochrobacterium sp. was immobilised on biochar (BIB), the hydrocarbon removal was greater than BC by 5533 mg/kg and 1607 mg/kg at weeks 10 and 22, respectively. However, when BIB was co-applied with fertiliser (BIBF), hydrocarbon removal was lower than BIB alone by 6987-11,767 mg/kg. Quantitative PCR (q-PCR) analysis revealed that the gene related to Ochrobacterium sp. was higher in BIB than in the BC treatment, which likely contributed to higher hydrocarbon removal in the BIB treatment. The results of the q-PCR analysis for the presence of alkB genes and FTIR analysis suggest that the degradation of alkane contributed to hydrocarbon removal. The findings of this study demonstrate that bacterial immobilisation on biosolids-derived biochar is a promising technique for the remediation of diesel-contaminated soil. Future studies should focus on optimising the immobilisation process for enhanced hydrocarbon removal.

Isolation and identification of metallotolerant bacteria with a potential biotechnological application

Mining has led to severe environmental pollution in countries with exhaustive mining production and inadequate industrial waste regulation. Microorganisms in contaminated sites, like mine tailings, have adapted to high concentrations of heavy metals, developing the capacity of reducing or removing them from these environments. Therefore, it is essential to thoroughly characterize bacteria present in these sites to find different ways of bioremediation. In this regard, in this study, an enrichment and isolation procedure were performed to isolate bacteria with lower nutritional requirements and high tolerance to Cu(II) and Fe(II) from two Sonoran River basin mining tails. Two Staphylococcus species and a Microbacterium ginsengisoli strain were isolated and identified from the San Felipe de Jesús mining tail. Also, three strains were isolated from the Nacozari de García mining tail: Burkholderia cenocepacia, Sphingomonas sp. and Staphylococcus warneri. Significant microbiological differences were found between the two sites. All these species exhibited tolerance up to 300 mg/L for Cu (II)–Fe (II) solutions, indicating their capacity to grow in these conditions. Moreover, a consortium of isolated bacteria was immobilized in two different biocomposites and the biocomposite with larger pore size achieved greater bacterial immobilization showcasing the potential of these bacteria in biotechnological applications.

Invasive plant-derived biochar for sustainable bioremediation of pesticide contaminated soil

Managing invasive plant presents a significant challenge to both the environment and the economy. There is an opportunity to address this issue by utilizing invasive plants as a sustainable and cost-effective source of valuable functional materials for environmental remediation. In this study, a promising Mikania micrantha biochar (MB) was synthesized by pyrolyzing an invasive plant, which was utilized for bacterial immobilization and adsorption of contaminants. By embedding Proteus terrae ZQ02-MB within a polyvinyl alcohol-sodium alginate gel to create a biochar-modified bacterial microsphere (BBM), the superior degradation of pesticide contaminants was observed. Taking chlorothalonil (CHT) as an example, field experiments demonstrated that BBM achieved a removal efficiency of 59.8% by the third day. Additionally, BBM not only improved the richness and diversity of soil bacteria but also enhanced the microbial community structure by the seventh day. On this basis, the adsorption capacity of MB, biofilm growth promoting ability of BBM, and the CHT mineralization ability of strain ZQ02 were validated as a joint mechanism to promote efficient CHT removal. Overall, this study proposes a composite model of invasive plant-derived biochar loaded microorganisms, which has great potential in eliminating pollutant residues and paves new paths to develop strategies for reusing invasive species resources.

Development and assessment of an immobilized bacterial alliance that efficiently degrades tylosin in wastewater.

Microbial degradation of tylosin (TYL) is a safe and environmentally friendly technology for remediating environmental pollution. Kurthia gibsonii (TYL-A1) and Klebsiella pneumonia (TYL-B2) were isolated from wastewater; degradation efficiency of the two strains combined was significantly greater than either alone and resulted in degradation products that were less toxic than TYL. With Polyvinyl alcohol (PVA)-sodium alginate (SA)-activated carbon (AC) used to form a bacterial immobilization carrier, the immobilized bacterial alliance reached 95.9% degradation efficiency in 1 d and could be reused for four cycles, with > 93% degradation efficiency per cycle. In a wastewater application, the immobilized bacterial alliance degraded 67.0% TYL in 9 d. There were significant advantages for the immobilized bacterial alliance at pH 5 or 9, with 20 or 40 g/L NaCl, or with 10 or 50 mg/L doxycycline. In summary, in this study, a bacterial consortium with TYL degradation ability was constructed using PVA-SA-AC as an immobilized carrier, and the application effect was evaluated on farm wastewater with a view to providing application guidance in environmental remediation.

In Situ Measurements of Dynamic Bacteria Transport and Attachment in Heterogeneous Sand-Packed Columns.

Prevention, mitigation, and regulation of bacterial contaminants in groundwater require a fundamental understanding of the mechanisms of transport and attachment in complex geological materials. Discrepancies in bacterial transport behaviors observed between field studies and laboratory experiments indicate an incomplete understanding of dynamic bacterial transport and immobilization processes in realistic heterogeneous geologic systems. Here, we develop a new experimental approach for in situ quantification of dynamic bacterial transport and attachment distribution in geologic media that relies on radiolabelingEscherichia coliwith positron-emitting radioisotopes and quantifying transport with three-dimensional (3D) positron emission tomography (PET) imaging. Our results indicate that the highest bacterial attachment occurred at the interfaces between sand layers oriented orthogonal to the direction of flow. The predicted bacterial attachment from a 3D numerical model matched the experimental PET results, highlighting that the experimentally observed bacterial transport behavior can be accurately captured with a distribution of a first-order irreversible attachment model. This is the first demonstration of the direct measurement of attachment coefficient distributions from bacterial transport experiments in geologic media and provides a transformational approach to better understand bacterial transport mechanisms, improve model parametrization, and accurately predict how local geologic conditions can influence bacterial fate and transport in groundwater.

The Impact of Amine-Functionalised Iron Oxide Nanoparticles on the Menaquinone-7 Isomer Profile and Production of the Bioactive Isomer

The K family of vitamins includes a collection of molecules with different pharmacokinetic characteristics. Menaquinone-7 (MK-7) has the finest properties and is the most therapeutically beneficial due to its long plasma half-life and outstanding extrahepatic bioavailability. MK-7 exhibits cis–trans isomerism, and merely the all-trans form is biologically efficacious. Therefore, the remedial value of MK-7 end products is exclusively governed by the quantity of all-trans MK-7. Consumers favour fermentation for the production of MK-7; however, it involves several challenges. The low MK-7 yield and extensive downstream processing requirements increase production costs, resulting in an expensive final product that is not universally available. Bacterial cell immobilisation with iron oxide nanoparticles (IONs) can potentially address the limitations of MK-7 fermentation. Uncoated IONs tend to have low stability and can adversely affect cell viability; thus, amine-functionalised IONs, owing to their increased physicochemical stability and biocompatibility, are a favourable alternative. Nonetheless, employing biocompatible IONs for this purpose is only advantageous if the bioactive MK-7 isomer is obtained in the most significant fraction, exploring which formed the aim of this investigation. Two amine-functionalised IONs, namely 3-aminopropyltriethoxysilane (APTES)-coated IONs (IONs@APTES) and L-Lysine (L-Lys)-coated IONs (L-Lys@IONs), were synthesised and characterised, and their impact on various parameters was evaluated. IONs@APTES were superior, and the optimal concentration (300 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}g/mL) increased all-trans MK-7 production and improved its yield relative to the untreated cells by 2.3- and 3.1-fold, respectively. The outcomes of this study present an opportunity to develop an innovative and effective fermentation method that enhances the production of bioactive MK-7.

Enhancing fiber–matrix interface permeability resistance of natural fiber-reinforced, bio-cemented sand by CaCO[formula omitted] seed pretreatment

This study explores the application of roughness pretreatment on plant-based natural fiber surfaces to enhance the sealing effectiveness of the sand-fiber interfacial. The technique roughens the reinforced material by presetting CaCO3 seeds on the fiber surface, thereby immobilizing more bacteria as nucleation sites, further increasing the interfacial bonding area by promoting bio-mineralization and achieving efficient sealing of preferential flow channels. Experimental investigation was conducted to compare the promoting effects on bio-mineralization of reinforced sand with three pretreated fibers. Results showed that the fibers pretreated with CaCO3 could fill the pores to bridge sand particles more effectively by aggregating bio-mineralized precipitates around them. The bacterial immobilization rate and calcium carbonate content of bio-cemented sands with fiber pretreatment remarkably increased with increasing fiber surface roughness characterized by fractal dimension (Fd) when compared to the samples without pretreatment, and the maximum increase was 35.66% (coir, Fd=1.390) and 152.3% (jute, Fd=1.330). The profile water-conducting rate and average hydraulic conductivity have been reduced by 46% and 86%, Among the three fibers, ramie has the lowest hydraulic conductivity of 5.396 × 10−8m/s, which is lower than that of jute and coir (1.041 × 10−7m/s and 3.885 × 10−7m/s). Furthermore, the promotion of bacteria on bio-mineralization and more even distribution (upper, middle, and lower parts are 36%, 34%, and 30%, respectively) of CaCO3 were confirmed through bacteria staining testing and dye tracer testing. Finally, the effects of average flow velocity and shear rate on bacterial immobilization and sealing of preferential flow channels are discussed.

Impacts of biomimetic self-healing of Lysinibacillus boronitolerans immobilized through recycled fine and coarse brick aggregates in concrete

Recycling waste bricks for concrete is cost-effective and eco-friendly but may impact strength and durability. A promising solution is biomimetic self-healing concrete that uses bacteria to repair cracks. The efficacy of this approach is contingent upon the bacterial strain, carrier medium, medium size, and immobilization utilized. Nevertheless, it remains uncertain how carrier size affects biomimetic self-healing concrete when the same carrier substance and immobilization technique are used. This study explored using Lysinibacillus boronitolerans (LBBT) to develop biomimetic self-healing concrete using recycled fine brick aggregate (RFBA) as a carrier medium. Recycled coarse brick aggregate (RCBA) was also employed for the relative evaluation of the impact of carrier size in biocrete. Results revealed that adding LBBT to concrete through RFBA resulted in significant improvements in strength and toughness. Compressive, split tensile, and flexural strength increased by 16.2%, 17.6%, and 22.0% respectively, while compressive and flexural toughness improved by 51.0% and 27.6%. The abundant RFBA particles ensured the even distribution of LBBT throughout the mixture. RCBA immobilization facilitated self-healing, achieving 0.6 mm of crack healing with 89.7% compression strength recovery and a 26.0% healing potential. The achievement can be attributed to the macro-voids and the stiffened structure of RCBA. Additionally, forensic investigations confirm the presence of microbial induced carbonate precipitation. Thus, RFBA is a promising immobilizer for LLBT, exhibiting a greater impact on mechanical performance due to its smaller particle size. In contrast, RCBA facilitates self-healing by entrapping the biomimetic agent, despite its lower abundance.

Biodegradation characteristics of mixed phenol and p-cresol contaminants from a swine farm using bacteria immobilized in calcium alginate beads

Phenol and p-cresol, major odorous gases in swine farms, pose significant health risks and require efficient elimination. This study screened biofilm-derived bacteria from a local swine farm for effective phenol and p-cresol degradation. Isolated bacteria were exposed to 1000 ppm of phenol and p-cresol and cultivated in Mineral salts medium (MSM). Morphology, degradation characteristics, and 16S rRNA analysis were employed for identification. The isolate Proteobacteria and Actinobacteria, completely degraded phenol and p-cresol in water, up to 500 ppm, within 12 h. The mixtures of Proteobacteria and Actinobacteria eliminated 500 ppm of each compound within 28 h. Additionally, immobilized bacteria in calcium alginate beads exhibited reusable degradation activity for at least 5 cycles, with no decline in performance or bacterial loss. and no bacterial loss. This study highlights the potential of these bacterial strains and immobilization technique for effective VOC degradation in swine farm environments, improving odor control and environmental well-being.

Effect of incorporating discarded facial mask fiber on mechanical properties of MICP–treated sand

Responding to environmental challenges associated with the waste generated from discarded facial mask fiber (DFMF), this study introduces an innovative approach to integrate DFMF as a beneficial additive to Microbial-induced calcium carbonate precipitation (MICP) technology - an eco-friendly soil stabilization method. Despite its merit of enhancing soil strength and permeability, MICP often incurs substantial soil brittleness. The incorporation of DFMF, a material conventionally destined for landfill, demonstrates an enhancement in the ductility of MICP–treated sand. Various proportions of DFMF were incorporated (0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% by weight), leading to an observable improvement in unconfined compressive strength (UCS), splitting tensile strength (STS) and in the microstructural configuration of MICP-treated sand. The presence of DFMF fostered bacterial immobilization, catalyzed CaCO3 production, and culminated in an optimum DFMF content at 0.2%. This not only mitigated soil brittleness by introducing ductility via calcite precipitation but also culminated in a “sand particles-fibers-sand particles” spatial configuration, reducing the weakening effect of water on MICP-treated sand samples. This study, therefore, highlights the potential of DFMF as a promising additive in MICP-treated sand, thereby offering an effective method for recycling and reusing discarded facial mask fibers.

Degradation of aniline: sodium alginate/modified pomelo cellulose double cross-linking system as a bacterial immobilization carrier.

Pectin cellulose grafted with glycidyltrimethylammoniochloride (GTMAC) was successfully obtained following the processes of depectinfibrillation and cellulose cationization using ordinary Shatian pomelo peel produced in Yongzhou, Hunan, as the raw material. This is the first report on a new type of functionalized sodium alginate-immobilized material prepared from the fibers of pomelo peel. The material was prepared by combining modified pomelo peel cellulose and sodium alginate following the processes of physical and chemical double cross-linking. The prepared material was used to embed the target bacteria to achieve the biodegradation of p-aniline. The concentration of CaCl2 was adjusted when the alginate gelled, and the alginate to yuzu peel cellulose ratio was tuned. The immobilized material-embedded bacteria help achieve the best degradation effect. Bacteria are embedded during the process of the degradation of aniline wastewater, and the functionalization of the cellulose/sodium alginate-immobilized material results in unique surface structure performance. The performance of the prepared system is better than that of the single sodium alginate-based material characterized by a large surface area and good mechanical properties. The degradation efficiency of the system is improved significantly for the cellulose materials, and the prepared materials can potentially find applications in the field of bacteria-fixed technology.

Bacteria-Polymer Composite Material for Glycerol Valorization.

Bacterial immobilization is regarded as an enabling technology to improve the stability and reusability of biocatalysts. Natural polymers are often used as immobilization matrices but present certain drawbacks, such as biocatalyst leakage and loss of physical integrity upon utilization in bioprocesses. Herein, we prepared a hybrid polymeric matrix that included silica nanoparticles for the unprecedented immobilization of the industrially relevant Gluconobacter frateurii (Gfr). This biocatalyst can valorize glycerol, an abundant by-product of the biodiesel industry, into glyceric acid (GA) and dihydroxyacetone (DHA). Different concentrations of siliceous nanosized materials, such as biomimetic Si nanoparticles (SiNps) and montmorillonite (MT), were added to alginate. These hybrid materials were significantly more resistant by texture analysis and presented a more compact structure as seen by scanning electron microscopy. The preparation including 4% alginate with 4% SiNps proved to be the most resistant material, with a homogeneous distribution of the biocatalyst in the beads as seen by confocal microscopy using a fluorescent mutant of Gfr. It produced the highest amounts of GA and DHA and could be reused for up to eight consecutive 24 h reactions with no loss of physical integrity and negligible bacterial leakage. Overall, our results indicate a new approach to generating biocatalysts using hybrid biopolymer supports.

Optimization of whole-cell bacterial bioreporter immobilization on electrospun cellulose acetate (CA) and polycaprolactone (PCL) fibers for arsenic detection.

Arsenic contamination is a critical global problem, and its widespread environmental detection is becoming a prominent issue. Herein, electrospun fibers of cellulose acetate (CA) and polycaprolactone (PCL) were successfully fabricated and used as the support material for immobilization of arsenic-sensing bacterial bioreporter for the first time. To date, no attempt has been made to immobilize fluorescent whole-cell bioreporter cells on electrospun fibers for arsenic detection. CA and PCL electrospun fibers were fabricated via traditional electrospinning technique and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and contact angle meter. Following immobilization of the bacterial bioreporter cells, the immobilized bacteria were also characterized by viability assay using AlamarBlue. The effects of growth phase and cell concentration on the fluorescence response of fiber-immobilized arsenic bioreporters to arsenic were also investigated. After immobilization of arsenic bioreporters on 10 wt% PCL fiber, 91% of bacterial cells remained viable, while this value was 55.4% for cells immobilized on 12.5 wt% CA fiber. Bioreporter cells in the exponential growth phase were shown to be more sensitive to arsenic compared to aged cells. While both the electropsun PCL- and CA-immobilized bioreporters successfully detected 50 and 100µg/L of arsenite (As (III)) concentrations, the PCL-immobilized bioreporter showed better fluorescence performance which should be investigated in future studies. This study helps to fill some gaps in the literature and demonstrates the potential for using electrospun fiber-immobilized arsenic whole-cell bioreporter for arsenic detection in water.

Efficient Bioremediation of Petroleum-Contaminated Soil by Immobilized Bacterial Agent of Gordonia alkanivorans W33.

In this article, we report a method for preparing an immobilized bacterial agent of petroleum-degrading bacteria Gordonia alkanivorans W33 by combining high-density fermentation and bacterial immobilization technology and testing its bioremediation effect on petroleum-contaminated soil. After determining the optimal combination of MgCl2, CaCl2 concentration, and culture time in the fermentation conditions by conducting a response surface analysis, the cell concentration reached 7.48 × 109 CFU/mL by 5 L fed-batch fermentation. The W33-vermiculite-powder-immobilized bacterial agent mixed with sophorolipids and rhamnolipids in a weight ratio of 9:10 was used for the bioremediation of petroleum-contaminated soil. After 45 days of microbial degradation, 56.3% of the petroleum in the soil with 20,000 mg/kg petroleum content was degraded, and the average degradation rate reached 250.2 mg/kg/d.

Cleanup of Cr(VI)-polluted groundwater using immobilized bacterial consortia via bioreduction mechanisms

Cr(VI) bioreduction has become a remedial alternative for Cr(VI)-polluted site cleanup. However, lack of appropriate Cr(VI)-bioreducing bacteria limit the field application of the in situ bioremediation process. In this study, two different immobilized Cr(VI)-bioreducing bacterial consortia using novel immobilization agents have been developed for Cr(VI)-polluted groundwater remediation: (1) granular activated carbon (GAC) + silica gel + Cr(VI)-bioreducing bacterial consortia (GSIB), and (2) GAC + sodium alginate (SA) + polyvinyl alcohol (PVA) + Cr(VI)-bioreducing bacterial consortia (GSPB). Moreover, two unique substrates [carbon-based agent (CBA) and emulsified polycolloid substrate (EPS)] were developed and used as the carbon sources for Cr(VI) bioreduction enhancement. The microbial diversity, dominant Cr-bioreducing bacteria, and changes of Cr(VI)-reducing genes (nsfA, yieF, and chrR) were analyzed to assess the effectiveness of Cr(VI) bioreduction. Approximately 99% of Cr(VI) could be bioreduced in microcosms with GSIB and CBA addition after 70 days of operation, which caused increased populations of total bacteria, nsfA, yieF, and chrR from 2.9 × 108 to 2.1 × 1012, 4.2 × 104 to 6.3 × 1011, 4.8 × 104 to 2 × 1011, and 6.9 × 104 to 3.7 × 107 gene copies/L. In microcosms with CBA and suspended bacteria addition (without bacterial immobilization), the Cr(VI) reduction efficiency dropped to 60.3%, indicating that immobilized Cr-bioreducing bacteria supplement could enhance Cr(VI) bioreduction. Supplement of GSPB led to a declined bacterial growth due to the cracking of the materials. The addition of GSIB and CBA could establish a reduced condition, which favored the growth of Cr(VI)-reducing bacteria. The Cr(VI) bioreduction efficiency could be significantly improved through adsorption and bioreduction mechanisms, and production of Cr(OH)3 precipitates confirmed the occurrence of Cr(VI) reduction. The main Cr-bioreducing bacteria included Trichococcus, Escherichia-Shigella, and Lactobacillus. Results suggest that the developed GSIB bioremedial system could be applied to cleanup Cr(VI)-polluted groundwater effectively.