DBT degradation enhancement by decorating Rhodococcus erythropolis IGST8 with magnetic Fe3O4 nanoparticles

Enhancement of reduction of biodesulfurization end products by Paenibacillus strains

The work reported here aimed to enhance the reduction of the downstream intermediates 2-hydroxybiphenyl (2-HBP) and 2-(2'hydroxyphenyl ethan-1-al) produced by biodesulfurization of DBT (dibenzothiophene) and BT (benzothiophene) using Paenibacillus strains (32O-W and 32O-Y). Salicylaldehyde was used as a surrogate for 2-(2'hydroxybiphenyl ethan-1-al), as the two compounds are structurally very similar while the latter is not commercially available. Five strategies were tested using growth in media containing either 2-HBP or salicylaldehyde: use of single strain cultures, co-culturing, genetic engineering to express Vitreoscilla hemoglobin (VHb), cell immobilization, and nanoparticle coating of cells. Cell growth and reduction of 2-HBP and salicylaldehyde were measured during 96 h of culturing. Regarding 2-HBP reduction, 32O-Y was generally better than 32O-W (about 50% for free cells, and as much as 16% for immobilized cells, and 24% for coated cells); co-culturing did not provide any consistent advantage, while VHb expression increased utilization only for 32O-W (by about 50%). Immobilization and coating resulted in large improvements for both strains (as much as 3700%). Free, immobilized, and coated cells of 32O-Y all removed salicylaldehyde, while only immobilized 32O-W cells were able to do so. For 32O-Y, co-culturing and coating, but not VHb expression, resulted in improvements in salicylaldehyde reduction (of up to 31%). Thus, alginate immobilization or nanoparticle coating of bacterial cells may be useful approaches for enhancing the reduction of DBT or BT biodesulfurization end products, and thus the overall biodesulfurization process for petroleum and petroleum products.

Extracellular production of azurin by reusable magnetic Fe3O4 nanoparticle-immobilized Pseudomonas aeruginosa

Azurin, found in the periplasm of Pseudomonas aeruginosa, has garnered significant attention as a potential anticancer agent in recent years. High-level secretion of proteins into the culture medium, offers a significant advantage over periplasmic or cytoplasmic expression. In this study, for the first time, P. aeruginosa cells were immobilized with magnetic nanoparticles (MNPs) to ensure effective, simple and quick separation of the cells and secretion of periplasmic azurin protein to the culture medium. For this purpose, polyethyleneimine-coated iron oxide (Fe3O4@PEI) MNPs were synthesized and MNPs containing Fe up to 600 ppm were found to be non-toxic to the bacteria. The highest extracellular azurin level was observed in LB medium compared to peptone water. The cells immobilized with 400 ppm Fe-containing MNPs secreted the highest protein. Lastly, the immobilized cells were found suitable for azurin secretion until the sixth use. Thus, the magnetic nanoparticle immobilization method facilitated the release of azurin as well as the simple and rapid separation of cells. This approach, by facilitating protein purification and enabling the reuse of immobilized cells, offers a cost-effective means of protein production, reducing waste cell formation, and thus presents an advantageous method.

Understanding Nanoscale Interactions between Minerals and Microbes: Opportunities for Green Remediation of Contaminated Sites

In situ contaminant degradation and detoxification mediated by microbes and minerals is an important element of green remediation. Improved understanding of microbe-mineral interactions on the nanoscale offers promising opportunities to further minimize the environmental and energy footprints of site remediation. In this Perspective, we describe new methodologies that take advantage of an array of multidisciplinary tools─including multiomics-based analysis, bioinformatics, machine learning, gene editing, real-time spectroscopic and microscopic analysis, and computational simulations─to identify the key microbial drivers in the real environments, and to characterize in situ the dynamic interplay between minerals and microbes with high spatiotemporal resolutions. We then reflect on how the knowledge gained can be exploited to modulate the binding, electron transfer, and metabolic activities at the microbe-mineral interfaces, to develop new in situ contaminant degradation and detoxication technologies with combined merits of high efficacy, material longevity, and low environmental impacts. Two main strategies are proposed to maximize the synergy between minerals and microbes, including using mineral nanoparticles to enhance the versatility of microorganisms (e.g., tolerance to environmental stresses, growth and metabolism, directed migration, selectivity, and electron transfer), and using microbes to synthesize and regenerate highly dispersed nanostructures with desired structural/surface properties and reactivity.

Advanced bioremediation by an amalgamation of nanotechnology and modern artificial intelligence for efficient restoration of crude petroleum oil-contaminated sites: a prospective study

Crude petroleum oil spillage is becoming a global concern for environmental pollution and poses a severe threat to flora and fauna. Bioremediation is considered a clean, eco-friendly, and cost-effective process to achieve success among the several technologies adopted to mitigate fossil fuel pollution. However, due to the hydrophobic and recalcitrant nature of the oily components, they are not readily bioavailable to the biological components for the remediation process. In the last decade, nanoparticle-based restoration of oil-contaminated, owing to several attractive properties, has gained significant momentum. Thus, intertwining nano- and bioremediation can lead to a suitable technology termed 'nanobioremediation' expected to nullify bioremediation's drawbacks. Furthermore, artificial intelligence (AI), an advanced and sophisticated technique that utilizes digital brains or software to perform different tasks, may radically transfer the bioremediation process to develop an efficient, faster, robust, and more accurate method for rehabilitating oil-contaminated systems. The present review outlines the critical issues associated with the conventional bioremediation process. It analyses the significance of the nanobioremediation process in combination with AI to overcome such drawbacks of a traditional approach for efficiently remedying crude petroleum oil-contaminated sites.

Use of nanoparticle-coated bacteria for the bioremediation of organic pollution: A mini review

Nanoparticle (NP)-coated (immobilized) bacteria are an effective method for treating environmental pollution due to their multifarious benefits. This review collates a vast amount of existing literature on organic pollution treatment using NP-coated bacteria. We discuss the features of bacteria, NPs, and decoration techniques of NP-bacteria assemblies, with special attention given to the surface modification of NPs and connection mechanisms between NPs and cells. Furthermore, the performance of NP-coated bacteria was examined. We summarize the factors that affect bioremediation efficiency using coated bacteria, including pH, temperature, and agitation, and the possible mechanisms involving them are proposed. From future perspectives, suitable surface modification of NPs and wide application in real practice will make the NP-coated bacterial technology a viable treatment strategy.

Biodesulfurization of Dibenzothiophene by Decorating Rhodococcus erythropolis IGTS8 Using Montmorillonite/Graphitic Carbon Nitride

Fossil fuels are the main sources of human energy, but their combustion releases toxic compounds of sulfur oxide. In the oil industry, using the optimal methods to eliminate sulfur compounds from fossil fuels is a very important issue. In this study, the performance of montmorillonite/graphitic carbon nitride (a new hybrid nanostructure) in increasing the biodesulfurization activity of Rhodococcus erythropolis IGTS8 was investigated. X-ray diffraction, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy and transmission electron microscopy were used for the characterization of the nanoparticles. The effective factors in this process were determined. Optimum conditions for microorganisms were designed using the Design Expert software. Experiments were performed in a flask. The results indicated that the biodesulfurization activity of a microorganism in the presence of the nanostructure increases by 52%. In addition, in the presence of the nanostructure, the effective factors are: 1. concentration of the nanostructure; 2. concentration of sulfur; 3. cell concentration. In the absence of the nanostructure, the only effective factor is the concentration of sulfur. Through analysis of variance, the proposed models were presented to determine the concentration of the 2-hydroxy biphenyl produced by the microorganisms (biodesulfurization activity) in the presence and absence of the nanostructure. The proposed models were highly acceptable and consistent with experimental data. The results of a Gibbs assay showed that the biodesulfurization efficiency of in the presence of the nanostructure was increased by about 52%, which is a very satisfactory result. The biodesulfurization activity of decorated cells in a bioreactor showed a significant increase compared with nondecorated cells. Almost a two-fold improvement in biodesulfurization activity was obtained for decorated cells compared with free cells.

Insights into the recent advances in nano-bioremediation of pesticides from the contaminated soil

In the present scenario, the uncontrolled and irrational use of pesticides is affecting the environment, agriculture and livelihood worldwide. The excessive application of pesticides for better production of crops and to maintain sufficient food production is leading to cause many serious environmental issues such as soil pollution, water pollution and also affecting the food chain. The efficient management of pesticide use and remediation of pesticide-contaminated soil is one of the most significant challenges to overcome. The efficiency of the current methods of biodegradation of pesticides using different microbes and enzymes depends on the various physical and chemical conditions of the soil and they have certain limitations. Hence, a novel strategy is the need of the hour to safeguard the ecosystem from the serious environmental hazard. In recent years, the application of nanomaterials has drawn attention in many areas due to their unique properties of small size and increased surface area. Nanotechnology is considered to be a promising and effective technology in various bioremediation processes and provides many significant benefits for improving the environmental technologies using nanomaterials with efficient performance. The present article focuses on and discusses the role, application and importance of nano-bioremediation of pesticides and toxic pollutants to explore the potential of nanomaterials in the bioremediation of hazardous compounds from the environment.

A review on biosurfactant producing bacteria for remediation of petroleum contaminated soils

The discharge of potentially toxic petroleum hydrocarbons into the environment has been a matter of concern, as these organic pollutants accumulate in many ecosystems due to their hydrophobicity and low bioavailability. Petroleum hydrocarbons are neurotoxic and carcinogenic organic pollutants, extremely harmful to human and environmental health. Traditional treatment methods for removing hydrocarbons from polluted areas, including various mechanical and chemical strategies, are ineffective and costly. However, many indigenous microorganisms in soil and water can utilise hydrocarbon compounds as sources of carbon and energy and hence, can be employed to degrade hydrocarbon contaminants. Therefore, bioremediation using bacteria that degrade petroleum hydrocarbons is commonly viewed as an environmentally acceptable and effective method. The efficacy of bioremediation can be boosted further by using potential biosurfactant-producing microorganisms, as biosurfactants reduce surface tension, promote emulsification and micelle formation, making hydrocarbons bio-available for microbial breakdown. Further, introducing nanoparticles can improve the solubility of hydrophobic hydrocarbons as well as microbial synthesis of biosurfactants, hence establishing a favourable environment for microbial breakdown of these chemicals. The review provides insights into the role of microbes in the bioremediation of soils contaminated with petroleum hydrocarbons and emphasises the significance of biosurfactants and potential biosurfactant-producing bacteria. The review partly focusses on how nanotechnology is being employed in different critical bioremediation processes.

Improvement in desulfurization of dibenzothiophene and dibenzothiophene sulfone by Paenibacillus strains using immobilization or nanoparticle coating

AIMS

Biodesulfurization of fossil fuels is a promising technology for deep desulfurization. Previously we have shown that Paenibacillus strains 32O-W and 32O-Y can desulfurize dibenzothiophene (DBT) and DBT sulfone (DBTS) effectively. In this work, improvements in DBT and DBTS desulfurization by these strains were investigated through immobilization and nanoparticle coating of cells.

METHODS AND RESULTS

Paenibacillus strains 32O-W and 32O-Y immobilized in alginate gel beads or coated with Fe₃ O₄ magnetite nanoparticles were grown at various concentrations (0.1-2 mmol l^-1 ) of DBT or DBTS for 96 h. The production of 2-hydroxybiphenyl (2-HBP) from 4S pathway biotransformation of DBT or DBTS was measured. The highest amounts of 2-HBP production occurred at concentrations of 0.1 and 0.5 mmol l^-1 . Compared to planktonic cultures maximum 2-HBP production increased by 54 % for DBT and 90 % for DBTS desulfurization with immobilized strains, and 44 % for DBT and 66% for DBTS desulfurization by nanoparticle coated strains.

CONCLUSIONS

Nanoparticle coated and immobilized cells may be of use in efforts to increase the efficiency of biodesulfurization.

SIGNIFICANCE AND IMPACT OF STUDY

Alginate immobilization or nanoparticle coating of bacterial cells may be useful approaches for enhancement of biodesulfurization for eventual use at an industrial scale.

Nanobioremediation: A sustainable approach for the removal of toxic pollutants from the environment

In recent years, the proportion of organic and inorganic contaminants has increased rapidly due to growing human interference and represents a threat to ecosystems. The removal of these toxic pollutants from the environment is a difficult task. Physical, chemical and biological methods are implemented for the degradation of toxic pollutants from the environment. Among existing technologies, bioremediation in combination with nanotechnology is the most promising and cost-effective method for the removal of pollutants. Numerous studies have shown that exceptional characteristics of nanomaterials such as improved catalysis and adsorption properties as well as high reactivity have been subjects of great interest. There is an emerging trend of employing bacterial, fungal and algal cultures and their components, extracts or biomolecules as catalysts for the sustainable production of nanomaterials. They can serve as facilitators in the bioremediation of toxic compounds by immobilizing or inducing the synthesis of remediating microbial enzymes. Understanding the association between microorganisms, contaminants and nanoparticles (NPs) is of crucial importance. In this review, we focus on the removal of toxic pollutants using the cumulative effects of nanoparticles with microbial technology and their applications in different domains. Besides, we discuss how this novel nanobioremediation technique is significant and contributes towards sustainability.

The effective removal of Congo Red using a bio-nanocluster: Fe3O4 nanoclusters modified bacteria

A bio-nanocluster (Fe₃O₄@bacteria) was prepared by simply mixture using the bacterial suspension and Fe₃O₄ nanoclusters to remove Congo red (CR) contamination from water resources. The bio-nanocluster was characterized by SEM, TEM and XPS. Adsorption efficiency, adsorption process and adsorption mechanism were comprehensively investigated. The maximum adsorption capacity (Q_m) of CR dye onto the Fe₃O₄@bacteria peaked at 320.1 mg/g, which was 2.88 times that of Fe₃O₄ under the same condition. Based on the equilibrium and kinetic studies, the Langmuir isotherm theory and pseudo-first-order model is appropriate to describe the adsorption process. The adsorption of CR is spontaneous and exothermic according to the thermodynamics parameters (ΔG^θ, ΔH^θ and ΔS^θ). The adsorption force dominated the Van der Waals force, biofloculation and chemisorption. The Fe₃O₄@bacteria could be applied potentially as an absorbent with high efficiency and environmentally friendly remediation of dyeing wastewater.

A Study of l-Lysine-Stabilized Iron Oxide Nanoparticles (IONPs) on Microalgae Biofilm Formation of Chlorella vulgaris

Despite iron-based nanoparticles gaining huge attraction in various field of sciences and technology, their application rises ecological concerns due to lack of studies on their interaction with microbial cells populations and communities, such as biofilms. In this study, Chlorella vulgaris cells were employed as a model of aquatic microalgae to investigate the impacts of l-lysine-coated iron oxide nanoparticles (lys@IONPs) on microalgal growth and biofilm formation. In this regard, C. vulgaris cells were exposed to different concentrations of lys@IONPs and the growth of cells was evaluated by OD600 and biofilm formation was analyzed using crystal violet staining throughout 12 days. It was revealed that low concentration of nanoparticles (< 400 µg/mL) can promote cell growth and biofilm formation. However, higher concentrations have an adverse effect on microalgal communities. It is interesting that microalgal growth and biofilm are concentration- and exposure time-dependent to lys@IONPs. Over long period (~ 12 days) exposure to high concentrations of nanoparticles, cells can adapt with the condition, so growth was raised and biofilm started to develop. Results of the present study could be considered in ecological issues and also bioprocesses using microalgal cells.

Impacts of Magnetic Immobilization on the Growth and Metabolic Status of Recombinant Pichia pastoris

Downstream processing is an expensive step for industrial production of recombinant proteins. Cell immobilization is known as one of the ideal solutions in regard to process intensification. In recent years, magnetic immobilization was introduced as a new technique for cell immobilization. This technique was successfully employed to harvest many bacterial and eukaryotic cells. But there are no data about the influence of magnetic immobilization on the eukaryotic inducted recombinant cells. In this study, impacts of magnetic immobilization on the growth and metabolic status of induced recombinant Pichia pastoris as a valuable eukaryotic model cells were investigated. Results based on colony-forming unit, OD600, and trypan blue assay indicated that magnetic immobilization had no adverse effect on the growth and viability of P. pastoris cells. Also, about 20-40% increase in metabolic activity was recorded in immobilized cells that were decorated with 0.5-2 mg/mL nanoparticles. Total protein and carbohydrate of the cells were also measured as main indicatives for cell function and no significant changes were observed in the immobilized cells. Current data show magnetic immobilization as a biocompatible technique for application in eukaryotic expression systems. Results can be considered for further developments in P. pastoris-based expression systems.

Access-dispersion-recovery strategy for enhanced mitigation of heavy crude oil pollution using magnetic nanoparticles decorated bacteria

Heavy crude oil (HCO) pollution has gained global attention, but traditional bioremediating practices demonstrate limited effectiveness. This study developed magnetic nanoparticles decorated bacteria (MNPB) using an oil-degrading and biosurfactant-producing Rhodococcus erythropolis species and identified a novel access-dispersion-recovery strategy for enhanced HCO pollution mitigation. The strategy entails (1) magnetic navigation of the MNPB towards HCO layer, (2) enhanced oil dispersion and formation of suspended oil-bacteria aggregates, and (3) magnetic recovery of these aggregates. The UV-spectrophotometer analysis showed that this strategy can enable up to 62% removal of HCO. The GC-MS analysis demonstrated that the MNPB enhanced the degradation of low-molecular-weight aromatics comparing with the pure bacteria, and the recovery process further removed oil-bacteria aggregates and entrained high-molecular-weight aromatics. The feasibility of using MNPB to mitigate HCO pollution could shed light on the emerging bioremediation applications.

Bioproduced Proteins On Demand (Bio-POD) in hydrogels using Pichia pastoris

Traditional production of industrial and therapeutic proteins by eukaryotic cells typically requires large-scale fermentation capacity. As a result, these systems are not easily portable or reusable for on-demand protein production applications. In this study, we employ Bioproduced Proteins On Demand (Bio-POD), a F127-bisurethane methacrylate hydrogel-based technique that immobilizes engineered Pichia pastoris for preservable, on-demand production and secretion of medium- and high-molecular weight proteins (in this case, SEAP, α-amylase, and anti-HER2). The gel samples containing encapsulated-yeast demonstrated sustained protein production and exhibited productivity immediately after lyophilization and rehydration. The hydrogel platform described here is the first hydrogel immobilization using a P. pastoris system to produce recombinant proteins of this breadth. These results highlight the potential of this formulation to establish a cost-effective bioprocessing strategy for on-demand protein production.

Zn2+-dependent enhancement of Atrazine biodegradation by Klebsiella variicola FH-1

Degradation efficiency of Atrazine by Klebsiella variicola FH-1 is improved by the addition of Zn²⁺. Both the chromosome and plasmid genomes of strain FH-1 were sequenced and annotated to identify genes involved in the degradation of Atrazine. Four open reading frames (ORFs) 1040, 2582, 3597, and 4043 encoding Zn²⁺-dependent hydrolases were knocked out to verify their predicted functions in the degradation of Atrazine. In the presence of Zn²⁺, the biodegradation efficiency of Atrazine by knockout mutant ∆ORF 3597 was 13.7% lower than that of wild type (WT) of strain FH-1 but still 9.4% higher than that of WT without Zn²⁺. These results indicated that ORF 3597 played a synergistic role but may not be the sole factor involved in the degradation of Atrazine. The enzymatic activities of pydC encoded by ORF 3597 were further characterized in the degradation of Atrazine. Results of fluorescence staining and flow cytometry analyses showed that the survival of bacterial cells and cell membrane permeability were increased in the presence of Zn²⁺ at different concentrations. Our study provided a scientific foundation for further investigation of the biological mechanisms of improving the degradation of Atrazine by strain FH-1 with the presence of Zn²⁺.

Elevated c-di-GMP levels promote biofilm formation and biodesulfurization capacity of Rhodococcus erythropolis

Bacterial biofilms provide high cell density and a superior adaptation and protection from stress conditions compared to planktonic cultures, making them a very promising approach for bioremediation. Several Rhodococcus strains can desulfurize dibenzothiophene (DBT), a major sulphur pollutant in fuels, reducing air pollution from fuel combustion. Despite multiple efforts to increase Rhodococcus biodesulfurization activity, there is still an urgent need to develop better biocatalysts. Here, we implemented a new approach that consisted in promoting Rhodococcus erythropolis biofilm formation through the heterologous expression of a diguanylate cyclase that led to the synthesis of the biofilm trigger molecule cyclic di-GMP (c-di-GMP). R. erythropolis biofilm cells displayed a significantly increased DBT desulfurization activity when compared to their planktonic counterparts. The improved biocatalyst formed a biofilm both under batch and continuous flow conditions which turns it into a promising candidate for the development of an efficient bioreactor for the removal of sulphur heterocycles present in fossil fuels.

Impacts of Magnetic Immobilization on the Recombinant Proteins Structure Produced in Pichia pastoris System

Pichia pastoris expression system was introduced with post-translation process similar to higher eukaryotes. Preliminary studies were performed toward process intensification and magnetic immobilization of this system. In this experiment, effects of magnetic immobilization on the structure of recombinant protein were evaluated. P. pastoris cell which express human serum albumin (HSA) was used as a model. The cells were immobilized with various concentrations of APTES coated magnetite nanoparticles. HSA production was done over 5 days induction and structure of the product was analyzed by UV-vis, fluorescence, and ATR-FTIR spectroscopy. Second derivative deconvolution method was used to analyze the secondary structure of HSA. P. pastoris cell that were immobilized with 0.5 and 1 mg/mL of nanoparticles were produced HSA with intact structure. But immobilization with 2 mg/mL of nanoparticles resulted in some modifications in the secondary structures (i.e., α-helixes and β-turns) of produced HSA. Based on these data, immobilization of P. pastoris cells with 0.5 or 1 mg/mL of nanoparticles is completely efficient for cell harvesting and has any effect on the structure of recombinant product. These findings revealed that decoration of microbial cells with high concentrations of nanoparticles has some impacts on the structure of secretory proteins.

Impact of magnetic immobilization on the cell physiology of green unicellular algae Chlorella vulgaris

Cell immobilization on the magnetic nanoparticles (MNPs) and magnetic harvesting is a novel approach for microalgal cells separation. To date, the effect of these nanoparticles on microalgal cells was only studied over a short period of time. More studies are hence needed for a better understanding of the magnetic harvesting proposes or environmental concerns relating to long-term exposure to nanoparticles. In this study, the impact of various concentrations of MNPs on the microalgal cells growth and their metabolic status was investigated over 12 days. More than 60% reduction in mitochondrial activity and pigments (chlorophyll a, chlorophyll b, and carotenoids) content occurred during the first 6 days of exposure to ≥50 µg/mL nanoparticles. However, more than 50% growth inhibitory effect was seen at concentrations higher than 400 µg/mL. Exposure to MNPs gradually induced cellular adaptation and after about 6 days of exposure to stress generating concentrations (˂400 µg/mL) of IONs, microalgae could overcome the imposed damages. This work provides a better understanding regarding the environmental impact of MNPs and appropriate concentrations of these particles for future algal cells magnetic immobilization and harvesting.

New Perspectives on Iron-Based Nanostructures

Among all minerals, iron is one of the elements identified early by human beings to take advantage of and be used. The role of iron in human life is so great that it made an era in the ages of humanity. Pure iron has a shiny grayish-silver color, but after combining with oxygen and water it can make a colorful set of materials with divergent properties. This diversity sometimes appears ambiguous but provides variety of applications. In fact, iron can come in different forms: zero-valent iron (pure iron), iron oxides, iron hydroxides, and iron oxide hydroxides. By taking these divergent materials into the nano realm, new properties are exhibited, providing us with even more applications. This review deals with iron as a magic element in the nano realm and provides comprehensive data about its structure, properties, synthesis techniques, and applications of various forms of iron-based nanostructures in the science, medicine, and technology sectors.

Effects of Modified Magnetite Nanoparticles on Bacterial Cells and Enzyme Reactions

Current paper presents biological effects of magnetite nanoparticles (MNPs). "Relations of MNP' characteristics (zeta-potential and hydrodynamic diameters) with effects on bacteria and their enzymatic reactions were the main focus.". Photobacterium phosphoreum and bacterial enzymatic reactions were chosen as bioassays. Three types of MNPs were under study: bare Fe3O4, Fe3O4 modified with 3-aminopropyltriethoxysilane (Fe3O4/APTES), and humic acids (Fe3O4/HA). Effects of the MNPs were studied at a low concentration range (< 2 mg/L) and attributed to availability and oxidative activity of Fe3+, high negative surface charge, and low hydrodynamic diameter of Fe3O4/HA, as well as higher Fe3+ content in suspensions of Fe3O4/HA. Low-concentration suspensions of bare Fe3O4 provided inhibitory effects in both bacterial and enzymatic bioassays, whereas the MNPs with modified surface (Fe3O4/APTES and Fe3O4/HA) did not affect the enzymatic activity. Under oxidative stress (i.e., in the solutions of model oxidizer, 1,4-benzoquinone), MNPs did not reveal antioxidant activity, moreover, Fe3O4/HA demonstrated additional inhibitory activity. The study contributes to the deeper understanding of a role of humic substances and silica in biogeochemical cycling of iron. Bioluminescence assays, cellular and enzymatic, can serve as convenient tools to evaluate bioavailability of Fe3+ in natural dispersions of iron-containing nanoparticles, e.g., magnetite, ferrihydrite, etc.

Biotransformation of benzaldehyde into L-phenylacetylcarbinol using magnetic nanoparticles-coated yeast cells

OBJECTIVES

The yeast cells were coated with Fe₃O₄ magnetic nanoparticles and employed as biocatalyst for the microbial biotransformation of benzaldehyde into L-phenylacetylcarbinol (L-PAC).

RESULTS

Saccharomyces cerevisiae CEN.PK113-7D yeast cells were coated with magnetic nanoparticles to facilitate the cells separation process. Transmission electron microscopy, powder XRD diffraction, and vibrating sample magnetometer were used to characterize magnetic nanoparticles and magnetic nanoparticle-coated yeast cells. Then the reusability of magnetically recoverable cells in production of L-PAC was investigated. Results show that coating yeast cells with magnetic nanoparticles does not affect their size and structure. Coated cells were also used in seven consecutive batch cycles and no significant reduction for L-PAC titer was observed in any of the cycles.

CONCLUSION

Coating yeast cells with magnetic nanoparticles enabled rapid separation and reuse of cells in several successive batch cycle without affecting their ability to produce L-PAC.

Magnetic Immobilization of Pichia pastoris Cells for the Production of Recombinant Human Serum Albumin

Magnetic immobilization as a novel technique was used to immobilize recombinant Pichia pastoris (GS115 Albumin) cells to produce human serum albumin (HSA). In this regard, magnetic nanoparticles (MNPs) coated with amino propyl triethoxy silane (APTES) were synthesized. P. pastoris cells were decorated with MNPs via nonspecific interactions. Decorated cells were magneto-responsible and easily harvested by applying an external magnetic field. The efficiency of magnetic immobilization (E_i) for cell removal was in direct relation with the MNP concentration and time of exposure to the magnetic field. By increasing the nanoparticles concentration, cells were harvested in a shorter period. Complete cell removal (E_i ≈ 100) was achieved in ≥0.5 mg/mL of MNPs in just 30 s. HSA is produced in an extremely high cell density (OD ~20) and it is the first time that magnetic immobilization was successfully employed for harvesting such a thick cell suspension. After 5 days of induction the cells, which were immobilized with 0.25 to 1 mg/mL of nanoparticles, showed an increased potency for recombinant HSA production. The largest increase in HSA production (38.1%) was achieved in the cells that were immobilized with 0.5 mg/mL of nanoparticles. These results can be considered as a novel approach for further developments in the P. pastoris-based system.

Exogenous Zn2+ enhance the biodegradation of atrazine by regulating the chlorohydrolase gene trzN transcription and membrane permeability of the degrader Arthrobacter sp. DNS10

Enhancing the biodegradation efficiency of atrazine, a kind of commonly applied herbicide, has been attracted much more concern. Here, Zn²⁺ which has long been considered essential in adjusting cell physiological status was selected to investigate its role on the biodegradation of atrazine by Arthrobacter sp. DNS10 as well as the transmembrane transport of atrazine during the biodegradation period. The results of gas chromatography showed that the atrazine removal percentages (initial concentration was 100 mg L^-1) in 0.05 mM Zn²⁺ and 1.0 mM Zn²⁺ treatments were 94.42% and 86.02% respectively at 48 h, while there was also 66.43% of atrazine left in the treatment without exogenous Zn²⁺ existence. The expression of atrazine chlorohydrolase gene trzN in the strain DNS10 cultured with 0.05 mM and 1.0 mM Zn²⁺ was 7.30- and 4.67- times respectively compared with that of the non-zinc treatment. In addition, the flow cytometry test suggests that 0.05 mM of Zn²⁺ could better adjust the membrane permeability of strain DNS10, meanwhile, the amount of atrazine accumulation in the strain DNS10 co-cultured with this level Zn²⁺ was 2.21 times of that of the strain without Zn²⁺. This study may facilitate a better understanding of the mechanisms that exogenous Zn²⁺ enhances the biodegradation of atrazine by Arthrobacter sp. DNS10.

Investigating the effect of starch/Fe3O4 nanoparticles on biodesulfurization using molecular dynamic simulation

The application of dibenzothiophene (DBT) as a source of energy leads to air pollution. The key solution to overcome this drawback is desulfurization. Magnetic nanoparticles have shown an excellent performance in the desulfurization of dibenzothiophene. In this study, molecular dynamic (MD) simulation was considered for the first time to gain insight about the molecule interactions in the biodesulfurization (BDS) process of DBT using Rhodococcus erythropolis IGTS8, in the presence and absence of starch/magnetic nanoparticles. According to the MD simulation results, the density of the system in the presence of starch/Fe₃O₄ was ascending while in the absence of these nanoparticles, the density was descending. Starch/magnetic nanoparticles caused more rapid equilibrium state in the biodesulfurization process. The energy diagram showed that magnetic nanoparticles decrease the energy fluctuation and increase the difference of non-bounding energy and potential energy (8 times) compared to (BDS) without nanoparticle, which reflects higher bounded energy in the system using starch/magnetic nanoparticles. The height of RDF peak in the presence of starch/Fe₃O₄ was 4 times more than the RDF peak in the absence of nanoparticle. In addition, the nanoparticles decreased the fluctuations around optimal temperature in BDS up to 5% compared to other state.

Immobilization of Cells by Magnetic Nanoparticles

Cell harvesting is one of the main expensive, labor-intensive, and energy-consuming steps in downstream processing. Cell immobilization has introduced as a valuable strategy for process intensification in biotechnological industries. Here we describe magnetic immobilization as a promising and novel technique for cell immobilization by using magnetic nanoparticles. This technique is based on the decoration of cells with magnetic nanoparticles to make them sensitive to magnetic field. So, the cells can be harvested simply by applying a magnetic separator.

Synthesis and Characterization of L-Lysin Coated Iron Oxide Nanoparticles as Appropriate Choices for Cell Immobilization and Magnetic Separation

Introduction:

Cell separation is one of the important steps of purification in downstream processes. Some separation techniques such as centrifugation and filtration are expensive and would affect cell viability. Magnetic separation can be a good alternative for laboratory and industrial cell separation processes.

Methods:

For this purpose, L-lysine coated Iron Oxide Nanoparticles (IONs) were synthesized and used for magnetic separation of Escherichia coli as the most applied microbial cell in biotechnological processes.

Results:

IONs have successfully decorated the bacterial cells and cells were completely separated by applying an external magnetic field.

Conclusion:

This study showed that coating of E. coli cells with IONs could help to isolate cells from culture media without using expensive instruments.

Investigation of Desulfurization Activity, Reusability, and Viability of Magnetite Coated Bacterial Cells

Background

Magnetic separation using magnetic nanoparticles can be used as a simple method to isolate desulfurizing bacteria from a biphasic oil/water system.

Objectives

Magnetite nanoparticles were applied to coat the surface of Rhodococcus erythropolis IGTS8 and Rhodococcus erythropolis FMF desulfurizing bacterial cells, and the viability and reusability of magnetite-coated bacteria evaluated by using various methods.

Material and Methods

Magnetite nanoparticles were synthesized through a reverse co-precipitation method. Glycine was added during and after the synthesis of magnetite nanoparticles to modify their surface and to stabilize the dispersion of the nanoparticles. The glycine-modified magnetite nanoparticles were immobilized on the surface of both oil-desulfurizing bacterial strains. Reusability of magnetite-coated bacterial cells was evaluated via assessing the desulfurization activity of bacteria via spectrophotometry using Gibb’s assay, after the separation of bacterial cells from 96h-cultures with the application of external magnetic field. In addition, CFU and fluorescence imaging were used to investigate the viability of magnetite-coated and free bacterial cells.

Results

TEM micrographs showed that magnetite nanoparticles have the size approximately 5.35±1.13 nm. Reusability results showed that both magnetite-coated bacterial strains maintain their activity even after 5 × 96h-cycles. The viability results revealed glycine-modified magnetite nanoparticles did not negatively affect the viability of two bacterial strains R. erythropolis IGTS8 and R. erythropolis FMF.

Conclusions

In conclusion, the glycine-modified magnetite nanoparticles have great capacity for immobilization and separation of desulfurizing bacteria from suspension.

An overview of conventional and alternative technologies for the production of ultra-low-sulfur fuels

Environmental concerns have given a great deal of attention for the production of ultra-low-sulfur fuels. The conventional hydrodesulfurization (HDS) process has high operating cost and also encounters difficulty in removing sulfur compound with steric hindrance. Consequently, various research efforts have been made to overcome the limitation of conventional HDS process and exploring the alternative technologies for deep desulfurization. The alternative processes being explored for the production of ultra-low-sulfur content fuel are adsorptive desulfurization (ADS), biodesulfurization (BDS), oxidative desulfurization (ODS), and extractive desulfurization (EDS). The present article provided the comprehensive information on the basic principle, reaction mechanism, workability, advantages, and disadvantages of conventional and alternative technologies. This review article aims to provide valuable insight into the recent advances made in conventional HDS process and alternative techniques. For deep desulfurization of liquid fuels, integration of conventional HDS with an alternative technique is also proposed.

Enhancement of bio-desulfurization capability of a newly isolated thermophilic bacterium using starch/iron nanoparticles in a controlled system

Due to the increasing application of oil and petroleum products, increased environmental contamination has become a matter of concern. Bio-desulfurization process may be used to eliminate sulfur from fossil fuels in the moderate condition. In this study, a thermophilic bacterium was isolated that was able to desulfurize dibenzothiophene. 16S rRNA sequencing indicated that this strain is related closely to Bacillus thermoamylovorans (97%). This strain grew in Basal salt medium containing DBT (100 mgl^-1) as the only sulfur source, at 55°C and showed maximum growth (OD₆₆₀ = 0.850) following 72 h incubation time. 2‑hydroxybiphenyl was produced at the maximal concentration (26.13 ± 0.12 mgl^-1) at 72 h. Bio-desulfurization and growth rate factors were optimized using response surface methodology. Starch/Fe₃O₄ and starch/Fe nanoparticles were used for enhancement of BDS efficiency. The size of starch/Fe₃O₄ and starch/Fe nanoparticles were 20 and 30-40 nm, respectively, as described by using scanning electron microscope and transmission electron microscope. The results showed that the immobilized cells by starch/Fe₃O₄ and starch/Fe nanoparticles had higher desulfurization capacity, about 10% and 22% more, respectively. Also, BDS in a bioreactor in the presence of nanoparticles was increased 25% with respect of the process occurred in the flask.

Two contrary roles of Fe3O4 nanoparticles on kinetic and thermodynamic of Paclitaxel degradation by Citrobacter amalonaticus Rashtia immobilized on sodium alginate gel beads

Roles of Fe₃O₄ nanoparticles (NPs) on biodegradation of Paclitaxel by Citrobacter amalonaticus immobilized on alginate gel beads were investigated. Limitation in substrate diffusion is the major drawback of the cell immobilization method. To overcome this problem, bacterial cells were immobilized on the gel beads containing different concentrations (5-20mg/mL) of Fe₃O₄ NPs and their Paclitaxel degrading potential at different temperatures was investigated using kinetic and thermodynamic modeling. Co-immobilization of bacterial cells with 5, 10 and 20mg/mL Fe₃O₄ NPs enhanced biodegradation efficiencies to 66%, 80% and 78%, respectively, compared to the NPs free immobilized cells (41.9%). The optimum concentration of Fe₃O₄ NPs (10mg/mL) had both inhibitory and accelerating effects on paclitaxel degradation depending on the incubation time and temperature. Increasing dose of Fe₃O₄ NPs could increase paclitaxel degradation, despite increasing of thermodynamic inhibitory factors, only when longer time and higher temperature were used. ΔG values increased about 11.2 KJ/mol at all temperatures of 285, 295 and 305K, and ΔH increased 54.4%, in comparison with the treatment without NPs. This indicates that, inclusion of Fe₃O₄ NPs into the immobilization gels can increase the local concentration of Paclitaxel (with OH₂⁺ groups) and bacterial accessibility to the substrate and thus enhance biodegradation efficiency.

Degradation of nonylphenol polyethoxylates by functionalized Fe3O4 nanoparticle-immobilized Sphingomonas sp. Y2

In this study, the efficiency of the nonylphenol polyethoxylates (NPEOs)-degrading bacterium Sphingomonas sp. strain Y2 was evaluated, which was immobilized by a novel system composed of polydopamine (PD)-coated Fe₃O₄ iron nanoparticles (IONPs). The PD-IONPs, with a distinct core-shell structure, relatively uniform size, and high saturation magnetization, were prepared for Y2 immobilization. The performance of Y2 was unaffected by this novel immobilization method, exhibiting 79.5% and 99.9% of NPEOs (500ppm) degradation efficiency at day 1 and 2, respectively. Furthermore, separation and recycling were more readily achieved for immobilized cells as compared to free cells. Immobilized cells retained over 70% of the original degradation activity after 6cycles of utilization. These results suggest that Y2-PD-IONPs can be potentially used for NPEOs-contaminated wastewater bioremediation.

CAPSULE

Immobilization of Sphingomonas sp. Y2 by functionalized PD-IONPs with easy separation, recycling utilization and high efficiency.

Magnetic immobilization of bacteria using iron oxide nanoparticles

Bacterial cell immobilization is a novel technique used in many areas of biosciences and biotechnology. Iron oxide nanoparticles have attracted much attention in bacterial cell immobilization due to their unique properties such as superparamagnetism, large surface area to volume ratio, biocompatibility and easy separation methodology. Adhesion is the basis behind many immobilization techniques and various types of interactions determine bacterial adhesion. Efficiency of bacterial cell immobilization using iron oxide nanoparticles (IONs) generally depends on the physicochemical properties of the IONs and surface properties of bacterial cells as well as environmental/culture conditions. Bacteria exhibit various metabolic responses upon interaction with IONs, and the potential applications of iron oxide nanoparticles in bacterial cell immobilization will be discussed in this work.

Impact of 3-Aminopropyltriethoxysilane-Coated Iron Oxide Nanoparticles on Menaquinone-7 Production Using B. subtilis

One of the major issues associated with industrial production of menaquinone-7 (MK–7) is the low fermentation yield. In this study, we investigated the effect of iron oxide nanoparticles coated with 3–aminopropyltriethoxysilane (IONs@APTES) on the production of MK–7 using B. subtilis (ATCC 6633). Decoration of B. subtilis cells with IONs@APTES significantly enhanced both MK–7 production and yield. An approximately two-fold increase in MK–7 production (41 mg/L) was observed in the presence of 500 µg/mL IONs@APTES, as compared to MK–7 production using untreated bacteria (22 mg/L). This paper, therefore, illustrates the immense biotechnological potential of IONs@APTES in increasing MK–7 concentration using B. subtilis, and its future role in bioprocess engineering.

Biodesulphurization of gasoline by Rhodococcus erythropolis supported on polyvinyl alcohol

A new biodesulphurization (BDS) method has been considered using Rhodococcus erythropolis supported on polyvinyl alcohol (PVA) for BDS of thiophene as a gasoline sulphur model compound in n-hexane as the solvent, subsequently this biocatalyst has been applied to BDS of gasoline samples. The obtained results according to UV-Spectrophotometer analysis at 240 nm showed that 97·41% of thiophene at the optimum condition of primary concentration 80 mg l^-1 , pH = 7, by 0·1 g of biocatalyst in 30°C and after 20 h of contact time has been degraded. These optimum conditions have been applied to gasoline BDS and the biodegradation of gasoline thiophenic compounds have been investigated by gas chromatography-mass spectrometry (GC-MS). According to GC-MS, thiophene and its 2-methyl, 3-methyl and 2- ethyl derivatives had acceptable biodegradation efficiencies of about 26·67, 21·03, 23·62% respectively. Also, benzothiophene that has been detected in a gasoline sample had 38·89% biodegradation efficiency at optimum conditions, so biomodification of PVA by R. erythropolis produces biocatalysts with an active metabolism that facilitates the interaction of bacterial strain with gasoline thiophenic compounds. The morphology and surface functional groups of supported R. erythropolis on PVA have been investigated by scanning electron microscope (SEM) and FT-IR spectroscopy respectively. SEM images suggest some regular layered shape for the supported bacteria. FT-IR spectra indicate a desirable interaction between bacterial cells and polymer supports. Also, the recovery of biocatalyst has been investigated and after three times of using in BDS activity, its biocatalytic ability had no significant decreases.

SIGNIFICANCE AND IMPACT OF THE STUDY

The biomodification of polyvinyl alcohol by Rhodococcus erythropolis described herein produces a new biocatalyst which can be used for significantly reducing the thiophenic compounds of gasoline and other fossil fuels. The immobilization process is to increase the biodegradation efficiency of cells and accelerating the biodesulphurization process.

DBT desulfurization by decorating Rhodococcus erythropolis IGTS8 using magnetic Fe3O4 nanoparticles in a bioreactor

Today, crude oil is an important source of energy and environmental contamination due to the continued use of petroleum products is a matter or urgent concern. In this work, two technological platforms, namely, the use of a robust desulfurizing bacteria and the use of nanotechnology to decorate the surface of the bacteria with nanoparticles (NP), were combined to enhance biodesulfurization (BDS). BDS is an ecologically friendly method for desulfurizing petroleum products while avoiding damage to the hydrocarbons due to the high temperatures normally associated with physical desulfurization methods. First, a bacterium known to be a good organism for desulfurization (Rhodococcus erythropolis IGTS8) was employed in cell culture to remove a recalcitrant sulfur molecule from a common sulfur-containing compound found in crude petroleum products (dibenzothiophene). 2-Hydroxybiphenyl (2-HBP) produced as a consequence of the BDS of dibenzothiophene was determined using Gibbs' assay. The synthesized NP were characterized by field emission scanning electron microscope, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, and vibrating sample magnetometer. The field emission scanning electron microscope and transmission electron microscopy images showed the size of the NP is 7-8 nm. The decorated cells had a long lag phase, but the growth continued until 148 h (at OD₆₀₀ = 3.408) while the noncoated bacteria grow until 96 h before entering the stationary phase at OD₆₀₀ = 2.547. Gibbs' assay results showed that production of 2-HBP by decorated cells was 0.210 mM at t = 148 h, while 2-HBP production by nondecorated cells was 0.182 mM at t = 96 h. Finally, the experiments were repeated in a fermenter.

Enhancement of algicidal properties of immobilized Bacillus methylotrophicus ZJU by coating with magnetic Fe₃O₄ nanoparticles and wheat bran

Algicidal bacteria offer a promising option for killing cyanobacteria. In this study, a newly isolated strain of Bacillus methylotrophicus, ZJU, was used to control Microcystis aeruginosa. Analyses of relative reactive oxygen level, malondialdehyde content, superoxide dismutase activity, and fluorescence staining indicated that oxidative damage caused by the algicidal supernatant of strain ZJU mainly affected the cell membrane and consequently the membrane permeability and membrane potential of M. aeruginosa cells. Furthermore, an embedded immobilization technique was employed to improve the practical application of strain ZJU as an algicidal agent. On this basis, we proposed a novel concept of enhancing the algicidal properties of immobilized ZJU by adding Fe3O4 nanoparticles and wheat bran in the process of immobilization. Our studies showed that Fe3O4 nanoparticles conferred the immobilized bacteria with a magnetization of 30.87 emu/g, and this magnetization enabled efficient re-collection of the immobilized bacteria by magnetic means. Moreover, wheat bran endowed the immobilized bacteria with 10.34% higher algicidal activity than immobilized bacteria without wheat bran. The results indicate a novel concept of enhancing the algicidal property of bacteria against M. aeruginosa by adding Fe3O4 nanoparticles and wheat bran.

Advances in the Reduction of the Costs Inherent to Fossil Fuels' Biodesulfurization towards Its Potential Industrial Application

Biodesulfurization (BDS) process consists on the use of microorganisms for the removal of sulfur from fossil fuels. Through BDS it is possible to treat most of the organosulfur compounds recalcitrant to the conventional hydrodesulfurization (HDS), the petroleum industry's solution, at mild operating conditions, without the need for molecular hydrogen or metal catalysts. This technique results in lower emissions, smaller residue production and less energy consumption, which makes BDS an eco-friendly process that can complement HDS making it more efficient. BDS has been extensively studied and much is already known about the process. Clearly, BDS presents advantages as a complementary technique to HDS; however its commercial use has been delayed by several limitations both upstream and downstream the process. This study will comprehensively review and discuss key issues, like reduction of the BDS costs, advances and/or challenges for a competitive BDS towards its potential industrial application aiming ultra low sulfur fuels.

Electrical resistivity tomography to monitor enhanced biodegradation of hydrocarbons with Rhodococcus erythropolis T902.1 at a pilot scale

Petroleum hydrocarbons (HC) represent the most widespread contaminants and in-situ bioremediation remains a competitive treatment in terms of cost and environmental concerns. However, the efficiency of such a technique (by biostimulation or bioaugmentation) strongly depends on the environment affected and is still difficult to predict a priori. In order to overcome these uncertainties, Electrical Resistivity Tomography (ERT) appears as a valuable non-invasive tool to detect soil heterogeneities and to monitor biodegradation. The main objective of this study was to isolate an electrical signal linked to an enhanced bacterial activity with ERT, in an aged HC-contaminated clay loam soil. To achieve this, a pilot tank was built to mimic field conditions. Compared to a first insufficient biostimulation phase, bioaugmentation with Rhodococcus erythropolis T902.1 led to a HC depletion of almost 80% (6900 to 1600ppm) in 3months in the center of the contaminated zone, where pollutants were less bioavailable. In the meantime, lithological heterogeneities and microbial activities (growth and biosurfactant production) were successively discriminated by ERT images. In the future, this cost-effective technique should be more and more transferred to the field in order to monitor biodegradation processes and assist in selecting the most appropriate remediation technique.

Nanotechnology Applied to the Biodesulfurization of Fossil Fuels and Spent Caustic Streams

The use of nanostructured materials in combination with desulfurizing microorganisms is a promising technique that would improve the desulfurization processes of gaseous fuels, oil, and some wastewater. Nanoparticles are highly versatile and tunable depending on the necessities of each particular contaminated media. The chapter shows the current technological options for the biodesulfurization of natural gas, oil and wastewater produced from the petroleum refining, where the application of nano-sized materials combined with desulfurizing microorganisms would improve the desulfurization capacities. In addition, advantages, disadvantages and opportunities of this hybrid technology are presented.

Synthesis and Application of Amine Functionalized Iron Oxide Nanoparticles on Menaquinone-7 Fermentation: A Step towards Process Intensification

Industrial production of menaquione-7 by Bacillus subtilis natto is associated with major drawbacks. To address the current challenges in menaquione-7 fermentation, studying the effect of magnetic nanoparticles on the bacterial cells can open up a new domain for intensified menqainone-7 process. This article introduces the new concept of production and application of l-lysine coated iron oxide nanoparticles (l-Lys@IONs) as a novel tool for menaquinone-7 biosynthesis. l-Lys@IONs with the average size of 7 nm were successfully fabricated and were examined in a fermentation process of l-Lys@IONs decorated Bacillus subtilis natto. Based on the results, higher menaquinone-7 specific yield was observed for l-Lys@IONs decorated bacterial cells as compared to untreated bacteria. In addition, more than 92% removal efficacy was achieved by using integrated magnetic separation process. The present study demonstrates that l-Lys@IONs can be successfully applied during a fermentation of menaquinone-7 without any negative consequences on the culture conditions. This study provides a novel biotechnological application for IONs and their future role in bioprocess intensification.