Universal Single-Step Approach to the Immobilization of Cyclodextrins in a Supercritical Medium for Capturing Drug, Dye, and Metal Nanoclusters.

By utilizing nanoreactor-like structures, the immobilization of macromolecules such as calixarenes and cyclodextrins (CD) with bucket-like structures provides new possibilities for engineered surface-molecule systems. The practical use of any molecular system depends on the availability of a universal procedure for immobilizing molecules with torus-like structures on various surfaces while maintaining identical operating parameters. There are currently several steps, including toxic solvent-based approaches using modified ß-CD to covalently attach to surfaces with multistep reactions. However, the existing multistep process results in molecular orientation, restricts the accessibility of the hydrophobic barrel of ß-CD's for practical use, and is effectively unable to use the surfaces immobilized with ß-CD for a variety of applications. In this study, it was demonstrated that ß-CD attached to the oxide-based semiconductor and metal surfaces through a condensation reaction between the hydroxyl-terminated oxide-based semiconductor/metal oxide and ß-CD in supercritical carbon dioxide (SCCO2) as a medium. The primary benefit of SCCO2-assisted grafting of unmodified ß-CD on various oxide-based metal and semiconductor surfaces is that it is a simple, efficient, one-step process and that it is ligand-free, scalable, substrate-independent, and uses minimal energy. Various physical microscopy and chemical spectroscopic methods were used to analyze the grafted ß-CD oligomers. The application of the grafted ß-CD films was demonstrated by the immobilization of rhodamine B (RhB), a dye, and dopamine, a drug. The in situ nucleation and growth of silver nanoclusters (AgNCs) in the molecular systems were studied for antibacterial and tribological properties by utilizing the guest-host interaction ability of ß-CD.

Performance and economic evaluation of a pilot scale embedded ends-free membrane bioreactor (EEF-MBR).

In this work, an embedded ends-free membrane bioreactor (EEF-MBR) has been developed to overcome the fouling problem. The EEF-MBR unit has a novel configuration where a bed of granular activated carbon is placed in the bioreactor tank and fluidized by the aeration system. The performance of pilot-scale EEF-MBR was assessed based on flux and selectivity over 140 h. The permeate flux fluctuated between 2 and 10 L.m-2.h-1 under operating pressure of 0.07-0.2 bar when EEF-MBR was used to treat wastewater containing high organic matter. The COD removal efficiency was more than 99% after 1 h of operating time. Results from the pilot-scale performance were then used to design a large-scale EEF-MBR with 1200 m3.day-1 capacity. Economic analysis showed that this new MBR configuration was cost-effective when the permeate flux was set at 10 L.m-2.h-1. The estimated additional cost for the large-scale wastewater treatment was about 0.25 US$.m-3 with a payback period of 3 years. KEY POINTS: • Performance of new MBR configuration, EEF-MBR, was assessed in long term operation. • EEF-MBR shows high COD removal and relatively stable flux. • Cost estimation of large scale shows the cost effective EEF-MBR application.

Biofilm formation on copper and its control by inhibitor/biocide in cooling water environment.

The present study has successfully identified the nitrate reducing bacteria present in the cooling water system and also investigated the performance of industrially applied biocide and inhibitor on the bacterial inhibition. In order to carry out the objective of this study, facilities and methods such as 16S rRNA gene sequencing, Lowry assay, SEM, EIS, ICP-MS and weight loss analysis were being utilized. In this study, two out of the five morphologically dis- similar colonies identified through 16S rRNA gene sequencing, namely the Massilia timonae and the Pseudomonas, were being utilized in the biocorrosion study on copper metal. From the surface analysis using SEM demonstrated the phenomenon of biofilm formation on the copper surface. 2-methylbenzimidazole has the addition of methyl group in the diazole ring position of benzimidazole it has create basicity environment and inhibit the metal deterioration. Meanwhile, it is also deducible from the EIS and protein analysis that com- bination of biocide with either of the inhibitors gives rise to better biocorrosion suppression (0.00178 mpy and 0.00171mpy) as compared to the sole effect of either biocide or inhibitor (0.00219 mpy, 0.00162 and 0.00143). Biocorrosion system biocide with MBM was found to exhibit 65% corrosion inhibition efficiency. Moreover, adoption of 2-Methylbenzimidazole seems to display better performance as compared to Multionic 8151, which is adopted in cooling water system.

Benefits and Biosafety of Use of 3D-Printing Technology for Titanium Biomedical Implants: A Pilot Study in the Rabbit Model.

BACKGROUND: Titanium has been used in osteosynthesis for decades and its compatibility and safety is unquestioned. Studies have shown that there is release and collection of titanium in the organ systems with little note of toxicity. The gold standard is considered to be titanium osteosynthesis plate produced by milling methods. The use of customized titanium plates produced with 3D printing, specifically direct metal laser sintering, have found increasing use in recent years. It is unknown how much titanium is released in these printed titanium implants, which is known to be potentially porous, depending on the heat settings of the printer. We hypothesize that the amount of titanium released in printed titanium implants may be potentially more or equal compared to the gold standard, which is the implant produced by milling. METHODS: We studied the biosafety of this technology and its products by measuring serum and organ titanium levels after implantation of 3D-printed versus traditionally fabrication titanium plates and screws in a pilot study using the rabbit model. A total of nine rabbits were used, with three each in the control, milled and printed titanium group. The animals were euthanized after six months. Serum and organs of the reticuloendothelial system were harvested, digested and assayed for titanium levels. RESULTS: Organ and serum titanium levels were significantly higher in rabbit subjects implanted with titanium implants (milled and printed) compared to the control group. However, there was no significant difference in organ and serum titanium levels of subjects implanted with milled and traditionally fabricated titanium implants. CONCLUSIONS: The biosafety of use of 3D-printed titanium implants and traditionally fabricated titanium implants are comparable. With this in mind, 3D-printed custom implants can not only replace, but will very possibly surpass traditionally fabricated titanium implants in the mode and extent of use.

Electrostatic interaction governed solute transport in forward osmosis.

Electrolytes are commonly employed as draw solutes in forward osmosis (FO). This work demonstrates that electrostatic interactions play a key role in ion transport in the FO process. The difference in diffusivity between the constituent ions of the draw electrolyte significantly impact the forward transport of the feed ions. Draw electrolyte composed of low-diffusivity cations and high diffusivity anions promoted forward transport of the feed anions and retarded that of the feed cation, and vice versa. The effects were remarkable even for the most commonly used draw electrolytes (NaCl or MgCl2), where the forward flux of NO3- and NO2- was found to increase by a few folds and that of NH4+ was reduced by similar magnitudes than that observed in a nonelectrolyte draw solute (glucose) system. More profound increase/reduction (up to 10 times) was observed for draw electrolytes composed of highly asymmetric cations and anions. An analytical model is developed by considering the electrostatic interaction between the draw and the feed ions, to predict its effect on the forward transport of the feed ions. The normalized diffusivity difference (θD) between the constituent ions of the draw electrolyte is found as a key factor that determines the transport behaviors of the feed ions. These results may have important implications in enhancing our understanding of bidirectional ion transport in FO. The findings may also be useful in the design and development of FO processes for enhanced removal of charged pollutants via draw solute selection and formulation.

Biocorrosion inhibition of Cu70:Ni30 by Bacillus subtilis strain S1X and Pseudomonas aeruginosa strain ZK biofilms.

Microbiologically influenced corrosion (MIC) or biocrorrosion is a cause of huge economic set back for industries around the globe. The present work deals with the study of corrosion of copper alloy (Cu-Ni 70:30) in the presence of bacterial biofilms produced by Bacillus subtilis strain S1X and Pseudomonas aeruginosa strain ZK. MIC was investigated using electrochemical techniques such as potentiodynamic polarization and electrochemical impedance spectroscopy, and through analytical techniques such as scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and atomic force microscopy (AFM). The Cu-Ni coupons were exposed to bacteria in minimal salt medium supplemented with NaCl for a period of 15 days. AFM and FTIR analysis revealed formation of a thick biofilm on the surface of the Cu alloy in bacterial inoculated systems. The electrochemical results demonstrated a decreased current density and corrosion rate for the systems with bacterial biofilms. These findings were supported by the results of SEM and weight loss studies. The results showed the inhibition of corrosion for Cu-Ni in biotic conditions (with biofilms) as compared with abiotic conditions (without biofilms).

Biocorrosion of mild steel and copper used in cooling tower water and its control.

The present study describes the biocorrosion of mild steel (MS1010) and pure copper (Cu) in cooling water environments (both field and lab study). Electrochemical and surface analyses of both metals were carried out to confirm the corrosion susceptibility in the presence of bacteria and inhibitor. Surface analysis of the MS and Cu coupons revealed that biofilm was developed with increasing exposure time in the field study. In the lab study, accumulation of extracellular polymeric substance over the metal surface was noticed and led to the severe pitting type of corrosion on both metal surfaces. Besides, the anti-corrosive study was carried out using the combinations of commercial corrosion inhibitor (S7653-10 ppm) with biocide (F5100-5 ppm), and the results reveal that the corrosion rate of MS and Cu was highly reduced to 0.0281 and 0.0021 mm/year (inhibitor system) than 0.1589 and 0.0177 mm/year (control system). Inhibition efficiency for both metals in the presence of inhibitor with biocide was found as 82 and 88% for MS and Cu, respectively. The present study concluded that MS was very susceptible to biocorrosion, compared to copper metal in cooling water environment. Further, the combination of the both inhibitor and biocide was effectively inhibiting the biocorrosion which was due to its antibacterial and anti-corrosive properties.

Chemically treated carbon black waste and its potential applications.

In this work, carbon black waste - a hazardous solid residue generated from gasification of crude oil bottom in refineries - was successfully used for making an absorbent material. However, since the carbon black waste also contains significant amounts of heavy metals (especially nickel and vanadium), chemical leaching was first used to remove these hazardous impurities from the carbon black waste. Acid leaching with nitric acid was found to be a very effective method for removal of both nickel and vanadium from the carbon black waste (i.e. up to 95% nickel and 98% vanadium were removed via treatment with 2M nitric acid for 1h at 20°C), whereas alkali leaching by using NaOH under the same condition was not effective for removal of nickel (less than 10% nickel was removed). Human lung cells (MRC-5) were then used to investigate the toxicity of the carbon black waste before and after leaching. Cell viability analysis showed that the leachate from the original carbon black waste has very high toxicity, whereas the leachate from the treated samples has no significant toxicity. Finally, the efficacy of the carbon black waste treated with HNO3 as an absorbent for dye removal was investigated. This treated carbon black waste has high adsorption capacity (∼361.2mg dye/g carbonblack), which can be attributed to its high specific surface area (∼559m2/g). The treated carbon black waste with its high adsorption capacity and lack of cytotoxicity is a promising adsorbent material. Moreover, the carbon black waste was found to show high electrical conductivity (ca. 10S/cm), making it a potentially valuable source of conductive material.

The potential of hybrid forward osmosis membrane bioreactor (FOMBR) processes in achieving high throughput treatment of municipal wastewater with enhanced phosphorus recovery.

Extensive research in recent years has explored numerous new features in the forward osmosis membrane bioreactor (FOMBR) process. However, there is an aspect, which is revolutionary but not yet been investigated. In FOMBR, FO membrane shows high rejection for a wide range of soluble contaminants. As a result, hydraulic retention time (HRT) does not correctly reflect the nominal retention of these dissolved contaminants in the bioreactor. This decoupling of contaminants retention time (CRT, i.e. the nominal retention of the dissolved contaminants) from HRT endows FOMBR a potential in significantly reducing the HRT for wastewater treatment. In this work, we report our results in this unexplored treatment potential. Using real municipal wastewater as feed, both a hybrid microfiltration-forward osmosis membrane bioreactor (MF-FOMBR) and a newly developed hybrid biofilm-forward osmosis membrane bioreactor (BF-FOMBR) achieved high removal of organic matter and nitrogen under HRT of down to 2.0 h, with significantly enhanced phosphorus recovery capacities. In the BF-FOMBR, the used of fixed bed biofilm not only obviated the need of additional solid/liquid separation (e.g. MF) to extract the side-stream for salt accumulation control and phosphorus recovery, but effectively quarantined the biomass from the FO membrane. The absence of MF in the side-stream further allowed suspended growth to be continuously removed from the system, which produced a selection pressure for the predominance of attached growth. As a result, a significant reduction in FO membrane fouling (by 24.7-54.5%) was achieved in the BF-FOMBR due to substantially reduced bacteria deposition and colonization.

Streptomycin favors biofilm formation by altering cell surface properties.

Studies have shown that external stress induces biofilm formation, but the underlying details are not clearly understood. This study investigates the changes in cell surface properties leading to increase in biofilm formation by Staphylococcus aureus and Pseudomonas aeruginosa in the presence of streptomycin. Bacterial attachment in the presence and absence of streptomycin was quantified by fluorescence spectroscopy. In addition, cell surface charge and contact angle were measured and the free energy barrier for attachment was modeled using extended Derjaguin-Landau-Verwey-Overbeek (xDLVO) theory. Peptides from bacterial cell surface were shaved by protease treatment and identified with ultra-performance liquid chromatography (UPLC)-QTOF and a homology search program SPIDER. Biofilm formation increased significantly in the presence of streptomycin (10 mg/L) in the culture. Bacterial cell surface charge reduced, and hydrophobicity increased leading to a net decrease in the free energy barrier for attachment. Extracellular matrix-binding protein was positively regulated in S. aureus under stress, indicating stronger interaction between bacterial cells and solid surface. In addition, several other proteins including biofilm regulatory proteins, multidrug efflux pumps, transporters, signaling proteins, and virulence factors were differentially expressed on bacterial cell surface, which is indicative of a strong stress response by bacteria to streptomycin treatment.

Towards high through-put biological treatment of municipal wastewater and enhanced phosphorus recovery using a hybrid microfiltration-forward osmosis membrane bioreactor with hydraulic retention time in sub-hour level.

This work uncovers an important feature of the forward osmosis membrane bioreactor (FOMBR) process: the decoupling of contaminants retention time (CRT) and hydraulic retention time (HRT). Based on this concept, the capability of the hybrid microfiltration-forward osmosis membrane bioreactor (MF-FOMBR) in achieving high through-put treatment of municipal wastewater with enhanced phosphorus recovery was explored. High removal of TOC and NH4(+)-N (90% and 99%, respectively) was achieved with HRTs down to 47min, with the treatment capacity increased by an order of magnitude. Reduced HRT did not affect phosphorus removal and recovery. As a result, the phosphorus recovery capacity was also increased by the same order. Reduced HRT resulted in increased system loading rates and thus elevated concentrations of mixed liquor suspended solids and increased membrane fouling. 454-pyrosequecing suggested the thriving of Bacteroidetes and Proteobacteria (especially Sphingobacteriales Flavobacteriales and Thiothrix members), as well as the community succession and dynamics of ammonium oxidizing and nitrite oxidizing bacteria.

Alkaline bioleaching of municipal solid waste incineration fly ash by autochthonous extremophiles.

The increasing demand for energy and the generation of solid waste have caused an alarming rise in fly ash production globally. Since heavy metals continue to be in demand for the production of materials, resource recovery from the recycling of these wastes has the potential to delay the depletion of natural ores. The use of microorganisms for the leaching of metals, in a process called bioleaching, is an eco-friendly and economical way to treat the metal-laden wastes. Bioleaching of fly ash is challenging due largely to the alkaline nature and toxic levels of heavy metals which are detrimental to microbial growth and bioleaching activity. The present work reports the isolation of indigenous bacteria from a local landfill site and their bioleaching performance [corrected]. 38 autochthonous strains of bacteria were isolated from eight samples collected and plated on five different media. 18 of the isolates showed bioleaching potential, with significant alkaline pH or fly ash tolerance. Genetic characterization of the strains revealed a dominance of Firmicutes, with Alkalibacterium sp. TRTYP6 showing highest fly ash tolerance of up to 20% w/v fly ash, and growth over a pH range 8-12.5. The organism selectively recovered about 52% Cu from the waste. To the best of our knowledge, this is the first time a study on bioleaching with extreme alkaliphiles is reported.

Investigation of extracellular polymeric substances (EPS) properties of P. aeruginosa and B. subtilis and their role in bacterial adhesion.

Extracellular polymeric substances (EPS) matrix in biofilm poses important functions such as a diffusion barrier to antimicrobial agents so that biofilm cells are more difficult to completely eliminate. Therefore, biofilm cells exhibit enhanced resilience unlike planktonic cells, and are more difficult to completely eliminate. In order to obtain a comprehensive understanding of bacterial adhesion to surfaces, knowledge of the composition and conformational properties of EPS produced during growth and biofilm formation is required, since their adhesive and conformational properties remain poorly understood at molecular level. Present study has provided further insights into identifying compositional and conformational properties of EPS produced by planktonic and biofilm cells of B. subtilis and P. aeruginosa. Various spectroscopy analyses showed that EPS produced by the two different species were chemically dissimilar. More proteinaceous compounds were present in EPS from B. subtilis, while EPS from P. aeruginosa were characterized by greater carbohydrate components. However, relative proportions of polysaccharides and/or proteins constituents varied with the growth mode of the bacteria. AFM was then used to probe the adhesive nature of EPS produced by the bacteria by using Single Molecule Force Spectroscopy (SMFS). Comparison of the two bacterial species indicated that the presence of polysaccharides promoted the adhesion strength of the EPS while proteins had lesser adherence effects. Comparison of the two growth modes for the same bacterial strain also indicated that greater EPS production and enhanced cellular adhesion are associated with biofilm growth.

Sequential biological process for molybdenum extraction from hydrodesulphurization spent catalyst.

Spent catalyst bioleaching with Acidithiobacillus ferrooxidans has been widely studied and low Mo leaching has often been reported. This work describes an enhanced extraction of Mo via a two stage sequential process for the bioleaching of hydrodesulphurization spent catalyst containing Molybdenum, Nickel and, Aluminium. In the first stage, two-step bioleaching was performed using Acidithiobacillus ferrooxidans, and achieved 89.4% Ni, 20.9% Mo and 12.7% Al extraction in 15 days. To increase Mo extraction, the bioleached catalyst was subjected to a second stage bioleaching using Escherichia coli, during which 99% of the remaining Mo was extracted in 25 days. This sequential bioleaching strategy selectively extracted Ni in the first stage and Mo in the second stage, and is a more environmentally friendly alternative to sequential chemical leaching with alkaline reagents for improved Mo extraction. Kinetic modelling to establish the rate determining step in both stages of bioleaching showed that in the first stage, Mo extraction was chemical reaction controlled whereas in the subsequent stage, product layer diffusion model provided the best fit.

Effects of CeO2 nanoparticles on system performance and bacterial community dynamics in a sequencing batch reactor.

The effects of CeO2 nanoparticles (NPs) on the system performance and the bacterial community dynamics in a sequencing batch reactor (SBR) were investigated, along with the fate and removal of CeO2 NPs within the SBR. Significant impact was observed on nitrification; NH4+-N removal efficiency decreased from almost 100% to around 70% after 6 days of continuous exposure to 1.0 mg/L of CeO2 NPs, followed by a gradual recovery until a stable value of around 90% after 20 days. Additionally, CeO2 NPs also led to a significant increase in the protein content in the soluble microbial products, showing the disruptive effects of CeO2 NPs on the extracellular polymeric substance matrix and related activated sludge structure. Denaturing gradient gel electrophoresis analysis showed remarkable changes in the bacterial community structure in the activated sludge after exposure to CeO2 NPs. CeO2 NPs were effectively removed in the SBR mainly via sorption onto the sludge. However, the removal efficiency decreased from 95 to 80% over 30 days. Mass balance evaluation showed that up to 50% of the NPs were accumulated within the activated sludge and were removed with the waste sludge.

Gold biorecovery from e-waste: An improved strategy through spent medium leaching with pH modification.

Rapid technological advancement and relatively short life time of electronic goods have resulted in an alarming growth rate of electronic waste which often contains significant quantities of toxic and precious metals. Compared to conventional recovery methods, bioleaching is an environmentally friendly process for metal extraction. Gold was bioleached from electronic scrap materials (ESM) via gold-cyanide complexation using cyanide produced from pure and mixed cultures of cyanogenic bacteria Chromobacterium violaceum, Pseudomonas aeruginosa and Pseudomonas fluorescens. As ESM was toxic to the bacteria, a two-step bioleaching approach was adopted where the solid waste was added to the bacterial culture after it has reached maximum growth and cyanide production during early stationary phase. Pure culture of C. violaceum showed the highest cyanide production, yielding maximum gold recovery of 11.3% at 0.5% w/v pulp density of ESM in two-step bioleaching. At the same pulp density of ESM, spent medium bioleaching using bacterial cell-free metabolites achieved gold recovery of 18%. Recovery increased to 30% when the pH of the spent medium was increased to shift the equilibrium in favor of cyanide ions production. It is demonstrated for the first time that pH modification of spent medium further improved metal solubilization and yielded higher metal recovery (compared to two-step bioleaching).

Presence of Pseudomonas aeruginosa influences biofilm formation and surface protein expression of Staphylococcus aureus.

Although Staphylococcus aureus and Pseudomonas aeruginosa can individually colonize and infect their hosts, the commensalistic effect of the two is more tenacious and lethal. In this study, it was shown that in co-culture with P. aeruginosa, a sub-population of S. aureus exhibited improved resistance to kanamycin by selection of small colony variant (SCV) phenotype. Additionally, biofilm formation by the two bacteria was denser in the co-culture, compared with biofilm formed in individual pure cultures. Using Atomic Force Microscope (AFM) force spectroscopy for single cells, it was demonstrated that S. aureus cultured in the presence of P. aeruginosa bound more tenaciously to substrates. Surface-shaved peptides were isolated and identified using ultra-performance liquid chromatography-quadrupole-time of flight and a homology search program spider. Results indicated that serine-rich adhesin, extracellular matrix binding protein and other putative adhesion proteins could be responsible for the enhanced attachment of S. aureus in the co-culture. Besides, several other proteins were differentially expressed, indicating the occurrence of a range of other interactions. Of particular interest was a multidrug resistant protein named ABC transporter permease which is known to expel xenobiotics out of the cells. Positive regulation of this protein could be involved in the SCV selection of S. aureus in the co-culture.

Direct and complete phosphorus recovery from municipal wastewater using a hybrid microfiltration-forward osmosis membrane bioreactor process with seawater brine as draw solution.

We report a hybrid microfiltration-forward osmosis membrane bioreactor (MF-FOMBR) for direct phosphorus recovery from municipal wastewater in the course of its treatment. In the process, a forward osmosis (FO) membrane and a microfiltration (MF) membrane are operated in parallel in a bioreactor. FO membrane rejects the nutrients (e.g., PO4(3-), Ca(2+), Mg(2+), etc.) and results in their enrichment in the bioreactor. The nutrients are subsequently extracted via the MF membrane. Phosphorus is then recovered from the nutrients enriched MF permeate via precipitation without addition of an external source of calcium or magnesium. The use of seawater brine as a draw solution (DS) is another novel aspect of the system. The process achieved 90% removal of total organic carbon and 99% removal of NH4(+)-N. 97.9% of phosphate phosphorus (PO4(3-)-P) was rejected by the FO membrane and enriched within the bioreactor. >90% phosphorus recovery was achieved at pH 9.0. The precipitates were predominantly amorphous calcium phosphate with a phosphorus content of 11.1-13.3%. In principal, this process can recover almost all the phosphorus, apart from that assimilated by bacteria for growth. Global evaluation showed an overall phosphorus recovery of 71.7% over 98 days.

Effects of ZnO nanoparticles on wastewater treatment and their removal behavior in a membrane bioreactor.

Long-term effects of ZnO nanoparticles on the system performance of an MBR were investigated together with their removal behavior in the system. Continuous operation over 242days showed that ZnO NPs at both 1.0 and 10.0mg/L caused moderate deterioration in the removal of COD, nitrogen and phosphorus. Denitrification was affected upon the exposure but recovered subsequently. Although no significant acute effect on ammonia-oxidization was observed, permanent inhibition occurred after long-term exposure. Nitrite-oxidization was not affected even with 10.0mg/L ZnO NPs. Significant changes were observed in activated sludge properties which resulted in severe membrane fouling. Although ZnO NPs caused changes in the bacteria community structure, the diversity however remain unchanged. ZnO NPs was removed effectively in the MBR (>98%) with biosorption being a major removal mechanism. Membrane filtration also played an important role (20% of the total removal) especially at high ZnO NPs concentrations (around 10.0mg/L).