• Characterizing the Cell Surface Properties of Hydrocarbon-Degrading Bacterial Strains, a Case Study

      Pouran, Hamid (Springer, 2019-03-29)
      This chapter describes some of the most common methods used to characterize the cell surface properties of the bacterial cells. As a case study, the focus of this chapter is on Sphingomonas spp., Sph2, which is a Gram negative and hydrophilic bacterial strain. The species used in this research was isolated from groundwater at a phenol-contaminated site. This hydrocarbon-degrading strain that can participate in bioremediation of polluted environments belongs to Sphingomonadaceae family. This group of bacteria is unique among Gram-negative cells because of having glycosphingolipids (GSL) instead of the lipopolysaccharide (LPS) layer in their cell wall. To characterize this strain, its surface properties were examined using potentiometric titration, modelling surface protonation sites using ProtoFit, zeta potential measurements, and attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. There is no published detailed study about cell wall characteristics of Sph2 yet, and this research reports such information for the first time. In addition, to investigate effects of the solution ionic strength on Sph2 adhesion behavior on metal oxides, its biofilm formation on hematite, as the model mineral, was evaluated in three different ionic strengths; ≈200 mM, 100 mM, and 20 mM. The ATR-FTIR analysis showed that despite the unique cell wall chemistry of Sph2 among the Gram-negative strains, its surface functional groups are similar to other bacterial species. Hydroxyl, carboxyl, phosphoryl, and amide groups were detected in Sph2 infrared spectra. The potentiometric titration results showed that Sph2 PZC is approximately 4.3. Optimizing the titration data based on ProtoFit non-electrostatic model (NEM) provided compatible results to the infrared spectroscopy analysis and four pKa values were identified; 3.9 ± 0.3, 5.9 ± 0.2, 8.9 ± 0.0, and 10.2 ± 0.1, which could be assigned to carboxyl, phosphate, amine, and hydroxyl groups, respectively. Zeta potential measurements demonstrated that changing the ionic strength from ≈200 mM to ≈20 mM shifts the zeta potential by ≈−20 mV. Direct observation showed that this alteration in the ionic strength coincides with a tenfold increase in the number of Sph2 attached cells to the hematite surface. This could be attributed to both electrostatic interactions between the cell and surface, and conformational changes of Sph2 surface biopolymers. In addition to reporting Sph2 cell wall characterization results for the first time, this study highlights importance of ionic strength in the cell adhesion to the mineral surfaces, which directly influence biofilm formation, bioremediation, and bacterial transport in aqueous systems.
    • Bacterial Cell-Mineral Interface, Its Impacts on Biofilm Formation and Bioremediation

      Pouran, Hamid (Springer, 2019-03-29)
      This chapter aims to provide a better understanding of the bacterial cell attachment and biofilm formation on the mineral surfaces, which would result in improving our knowledge about: the interfacial forces governing the bacterial cell attachment, predicting trends of the biofilm formation and consequently biodegradation rates, and the contaminant’s fate in the diverse geological media (Pouran HM. Studying molecular and nanoscale interactions at metal oxide surfaces and their effects on bacterial adhesion, 2009). In both aqueous and terrestrial environments, bacterial cells tend to be attached to a surface and form biofilm. If they are associated to, e.g., a mineral surface, bacterial cells would remain in a more stable microenvironment instead of being removed by the water shear stress. Even the bacterial planktonic phase can be considered as a mechanism for translocation from one surface to the other rather than a prime lifestyle (Watnick and Kolter 2000; Young 2006). The biofilm formation, which completely covers the surface, initially begins by the adhesion of a small quantity of cells (Vadillo-rodri et al. 2006; Pouran et al. 2017). Among the different indigenous microbial species in the contaminated environments, some are capable of degrading pollutants and participating in the environmental remediation process. The bioremediation process of the contaminated soils and waters is often considered a promising low risk management tool. Even when the contamination poses an imminent threat and other approaches are essential, bioremediation often is a viable secondary strategy for the site maintenance (Haws et al. 2006; Pouran et al. 2017). Natural environments are dynamic and complex systems; therefore, characterization and identifying the underlying processes governing the contaminant’s fate are not easy. Examples of the natural environments heterogeneity are the diverse physicochemical properties of the soils and aquifers matrices (Stumm and Morgan 1996). As the soils and sediments are the prime surfaces for the bacterial cell attachment in most natural environments, elucidation of the surface properties of these constituents and their role in initiating cell adhesion and biofilm formation are of the key importance in understanding the bioremediation process. In fact, the cell-mineral interface reactions not only influence the biodegradation process but many natural phenomena are affected by them. Understanding role of physicochemical interactions at the bacterial cells and minerals interface in the cell adhesion (as well as biofilm formation, development, and behavior) is essential for planning effective bioremediation techniques. It could potentially help us to predict the contaminants’ fate, and trends of the biodegradation rates in different environments. Consequently, the improved knowledge of the cell-mineral interface enable us to design and apply more sophisticated bioremediation techniques as a viable approach towards tackling the soil and water environmental pollution problems. Figure 1 schematically represents an aquifer and biofilm formation on some of the most abundant minerals in the environment, iron and aluminum oxides. It also indicates some the major effects of cell-mineral interface interactions on different environmental processes (Stumm and Morgan 1996; Zachara and Fredrickson 2004; Cornell and Schwertmann 2003).
    • Engineered Nanomaterials in the Environment, their Potential Fate and Behaviour and Emerging Techniques to Measure Them

      Pouran, Hamid (Springer, 2019-03-29)
      “There is plenty of room at the bottom” – this was title of Richard Feynman’s famous talk to the American Physical Society more than half a century ago. The Nobel Laureate, in his historic lecture, discussed the possibility of the direct manipulation of materials on the atomic and molecular level to unleash novel functions. Now, after decades of research, nanoscience faces a historic moment: moving from fundamental research towards a publically available technology, a turning point towards commercialization.
    • Species

      Kaburu, Stefano S. K (Springer, 2019-02-08)
    • The taxonomic history of the enigmatic Papuan snake genus Toxicocalamus (Elapidae: Hydrophiinae), with the description of a new species from the Managalas Plateau of Oro Province, Papua New Guinea, and a revised dichotomous key

      O'Shea, Mark; Allison, Allen; Kaiser, Hinrich (Societas Europaea Herpetologica, 2018-11-15)
      We trace the taxonomic history of Toxicocalamus, a poorly known genus of primarily vermivorous snakes found only in New Guinea and associated island archipelagos. With only a relatively limited number of specimens to examine, and the distribution of those specimens across many natural history collections, it has been a difficult task to assemble a complete taxonomic assessment of this group. As a consequence, research on these snakes has undergone a series of fits and starts, and we here present the first comprehensive chronology of the genus, beginning with its original description by George Albert Boulenger in 1896. We also describe a new species from the northern versant of the Owen Stanley Range, Oro Province, Papua New Guinea, and we present a series of comparisons that include heretofore underused characteristics, including those of unusual scale patterns, skull details, and tail tip morphology. Defined by the smallest holotype in the genus, the new species is easily differentiated from all other Toxicocalamus by a combination of the following eidonomic characters: fused prefrontal-internasal scute; single preocular, separate, not fused with prefrontal; minute circular, counter-sunk naris in the centre of a large, undivided, nasal scute; paired postoculars; single anterior temporal and paired posterior temporals; six supralabials, with 3rd and 4th supralabial contacting the orbit; dorsal scales in 15-15-15 rows; 235 ventral scales, 35 paired subcaudal scales; paired cloacal scales preceded by paired precloacal scales; and a short, laterally slightly compressed, ‘Ultrocalamus-type’ tail, terminating in a short conical scale. Differences from congeners in skull morphology include a reduced anterior extent of the parasphenoid, termination of the palatine tooth row at the anterior level of the parasphenoid, extent and shape of the premaxilla, shape and size of the prootics, extent and shape of the exoccipitals and occipital condyles, and features of the atlas-axis complex. This is the fifteenth species in the genus Toxicocalamus.
    • The crucial role of leucine concentration on spray dried mannitol-leucine as a single carrier to enhance the aerosolization performance of Albuterol sulfate

      Molina, Carlos; Kaialy, Waseem; Nokhodchi, Ali (Elsevier, 2018-11-09)
      Generally, DPI formulations show low fine particle fraction (FPF) due to poor detachment of drug particles from carrier during inhalation. l-Leucine, with varying concentrations (ranging from 0 to 10% w/w), were introduced into a 60%w/v mannitol solution where the solutions were then spray dried to achieve a new processed carrier. The spray dried samples were blended with Albuterol sulfate to determine the efficacy of their aerosolization performance. Analyzing each formulation was completed via the implementation of numerous analytical techniques such as particle size distribution analysis via laser diffraction, differential scanning calorimetry (DSC), scanning electron microscope (SEM), powder X-Ray diffraction (PXRD), Fourier transform infrared (FT-IR) spectroscopy, and an in vitro deposition study. It was shown the concentration of leucine in spray dried is really crucial to achieve the highest FPF possible. The highest FPF was obtained for the samples containing 10% w/w leucine which was 52.96 ± 5.21%. It was interesting to note that the presence of leucine produced different polymorphic forms for mannitol. Moreover, through this study, the authors were able to conclude that mannitol can serve as an alternative carrier in DPI formulations containing Albuterol sulfate tailored for lactose intolerant patients.
    • Atmin modulates Pkhd1 expression and may mediate autosomal recessive polycystic kidney disease (ARPKD) through altered non-canonical Wnt/planar cell polarity (PCP) signalling

      Richards, Taylor; Modarage, Kavindiya; Dean, Charlotte; McCarthy-Boxer, Aidan; Hilton, Helen; Esapa, Chris; Wilson, Patricia; Goggolidou, Paraskevi (Elsevier, 2018-11-07)
      Autosomal Recessive Polycystic Kidney Disease (ARPKD) is a genetic disorder with an incidence of ~1:20,000 that manifests in a wide range of renal and liver disease severity in human patients and can lead to perinatal mortality. ARPKD is caused by mutations in PKHD1, which encodes the large membrane protein, Fibrocystin, required for normal branching morphogenesis of the ureteric bud during embryonic renal development. The variation in ARPKD phenotype suggests that in addition to PKHD1 mutations, other genes may play a role, acting as modifiers of disease severity. One such pathway involves non-canonical Wnt/Planar Cell Polarity (PCP) signalling that has been associated with other cystic kidney diseases, but has not been investigated in ARPKD. Analysis of the AtminGpg6 mouse showed kidney, liver and lung abnormalities, suggesting it as a novel mouse tool for the study of ARPKD. Further, modulation of Atmin affected Pkhd1 mRNA levels, altered non-canonical Wnt/PCP signalling and impacted cellular proliferation and adhesion, although Atmin does not bind directly to the C-terminus of Fibrocystin. Differences in ATMIN and VANGL2 expression were observed between normal human paediatric kidneys and age-matched ARPKD kidneys. Significant increases in ATMIN, WNT5A, VANGL2 and SCRIBBLE were seen in human ARPKD versus normal kidneys; no substantial differences were seen in DAAM2 or NPHP2. A striking increase in E-cadherin was also detected in ARPKD kidneys. This work indicates a novel role for non-canonical Wnt/PCP signalling in ARPKD and suggests ATMIN as a modulator of PKHD1.
    • Metamaterial Superlenses Operating at Visible Wavelength for Imaging Applications

      Haxha, Shyqyri; AbdelMalek, Fathi; Ouerghi, Faouzi; Charlton, Martin; Aggoun, Amar; Fang, Xu (Nature Research, 2018-10-31)
      In this paper, a novel design for a metamaterial lens (superlens) based on a Photonic Crystal (PC) operating at visible wavelengths is reported. The proposed superlens consist of a gallium phosphide (GaP) dielectric slab waveguide with a hexagonal array of silver rods embedded within the GaP dielectric. In-house 2DFDTD numerical method is used to design and optimize the proposed superlens. Several superlenses are designed and integrated within a same dielectric platform, promoting the proof-of-concept (POC) of possible construction of an array of superlenses (or sub-lenses to create an M-Lens) for light field imaging applications. It is shown that the concavity of the superlens and positioning of each sub-lens within the array strongly affects the performances of the image in terms of resolution. Defects and various geometrical shapes are introduced to construct and optimize the proposed superlenses and increase the quality of the image resolution. It is shown that the orientation of the active region (ellipse) along x and y axis has tremendous influence on the quality of image resolution. In order to investigate the performance characteristics of the superlenses, transmitted power is calculated using 2D FDTD for image projections at various distances (in x and y plane). It is also shown, how the proposed superlens structures could be fabricated using standard micro fabrication techniques such as electron beam lithography, inductively coupled Reactive ion etching, and glancing angle evaporation methods. To the best of our knowledge, these are the first reported POC of superlenses, integrated in a monolithic platform suitable for high imaging resolution that can be used for light field imaging applications at visible wavelength. The proposed superlenses (integrated in a single platform M-Lens) will have tremendous impact on imaging applications.
    • Impacts of rising temperature, carbon dioxide concentration and sea level on wheat production in North Nile delta

      Kheir, A.; El Baroudy, A.A.; Aiad, M.A.; Zoghdan, M.G.; Abd El-Aziz, M.A.; Ali, M.G.M.; Fullen, M.A. (Elsevier B.V, 2018-10-16)
      Climate change poses a serious threat to arid and low elevation coastal zones. Kafrelsheikh governorate, as a large agricultural and coastal region on the Egyptian North Nile Delta, is one of the most vulnerable areas to higher temperature and global sea level rise. Two DSSAT wheat models (CERES and N-Wheat) were calibrated using a local cultivar (Misr3) grown under irrigated conditions in Egypt. Experimental data of two successive growing seasons during 2014/2015 and 2015/2016 were used for calibration using different treatments of irrigation, planting dates and fertilization. Both models simulated the phenology and wheat yield well, with root mean square deviation of b10%, and d-index N 0.80. Climate change sensitivity analysis showed that rising temperature by 1 °C to 4 °C decreased wheat yield by 17.6%. However, elevated atmospheric CO2 concentrations increased yield and could overtake some of the negative temperature responses. Sea level rise by 2.0 m will reduce the extent of agricultural land on the North Nile Delta of Egypt by ~60% creating an additional challenge to wheat production in this region.
    • Atmin mediates kidney morphogenesis by modulating Wnt signaling

      Goggolidou, P.; Hadjirin, N.F.; Bak, A.; Papakrivopoulou, E.; Hilton, H.; Norris, D.P.; Dean, C.H. (Oxford University Press, 2018-10-15)
      The DNA damage protein and transcription factor Atmin (Asciz) is required for both lung tubulogenesis and ciliogenesis. Like the lungs, kidneys contain a tubular network that is critical for their function and in addition, renal ciliary dysfunction has been implicated in the pathogenesis of cystic kidney disease. Using the Atmin mouse mutant Gasping6 (Gpg6), we investigated kidney development and found it severely disrupted with reduced branching morphogenesis, resulting in fewer epithelial structures being formed. Unexpectedly, transcriptional levels of key cilia associated genes were not altered in Atmin(Gpg6/Gpg6) kidneys. Instead, Gpg6 homozygous kidneys exhibited altered cytoskeletal organization and modulation of Wnt signaling pathway molecules, including β-catenin and non-canonical Wnt/planar cell polarity (PCP) pathway factors, such as Daam2 and Vangl2. Wnt signaling is important for kidney development and perturbation of Wnt signaling pathways can result in cystic, and other, renal abnormalities. In common with other PCP pathway mutants, Atmin(Gpg6/Gpg6) mice displayed a shortened rostral-caudal axis and mis-oriented cell division. Moreover, intercrosses between Atmin(Gpg6/+) and Vangl2(Lp/+) mice revealed a genetic interaction between Atmin and Vangl2. Thus we show for the first time that Atmin is critical for normal kidney development and we present evidence that mechanistically, Atmin modifies Wnt signaling pathways, specifically placing it as a novel effector molecule in the non-canonical Wnt/PCP pathway. The identification of a novel modulator of Wnt signaling has important implications for understanding the pathobiology of renal disease.
    • Genomic epidemiology of clinical Campylobacter spp. at a single health trust site

      Dunn, S.J.; Pascoe, B.; Turton, J.; Fleming, V.; Diggle, M.; Sheppard, S.K.; McNally, A.; Manning, G. (2018-10-11)
      Campylobacter is the leading cause of bacterial enteritis in the developed world, and infections with the organism are largely sporadic in nature. Links between sporadic cases have not been established, with the majority of infections thought to be caused by genetically distinct isolates. Using a read-mapping approach, 158 clinical isolates collected during 2014 from the greater Nottinghamshire area were analysed to assess the local population structure and investigate potential case linkages between sporadic cases of campylobacteriosis. Four instances (2.5 %) of case linkage were observed across the dataset. This study demonstrates that case linkage does occur between sporadic Campylobacter infections, and provides evidence that a dual multi-locus sequence typing/within-lineage single nucleotide polymorphism typing approach to Campylobacter genomic epidemiology provides a benefit to public-health investigations.
    • The Book of snakes

      O'Shea, Mark (Ivy Press, 2018-10-11)
      There are over 3,700 species of snake found on every continent except for Antarctica, ranging in size from Barbados’ tiny threadsnake to Southeast Asia’s massive reticulated python. More than any other creature snakes are surrounded by dark, compelling myths and legend, unsurprising since many constrict their prey to death, or kill with a venomous bite, using a diverse armory of venoms that affect the blood, tissues, organs, and respiration. However, it is especially true of snakes that the closer you observe them, the more exquisite they are in their intricate geometry of pattern, the fine texture of the overlapping scales, and the intricacies of their multifarious lifestyles. The Book of Snakes profiles 600 significant species from all 32 families—one in six of all known species—to create a beautiful collector’s piece that is both a significant resource for enthusiasts and scholars, and the most visually stimulating guide on the market.
    • Satellite-5G integration: a network perspective

      Giambene, Giovanni; Kota, Sastri; Pillai, Prashant (IEEE, 2018-09-27)
      Future 5G mobile communication systems are expected to integrate different radio access technologies, including the satellite component. Within the 5G framework, the terrestrial services can be augmented with the development of HTS systems and new mega-constellations meeting 5G requirements, such as high bandwidth, low latency, and increased coverage including rural areas, air, and seas. This article provides an overview of the current 5G initiatives and projects followed by a proposed architecture for 5G satellite networks where the SDN/NFV approach facilitates the integration with the 5G terrestrial system. In addition, a novel technique based on network coding is analyzed for the joint exploitation of multiple paths in such an integrated satellite-terrestrial system. For TCP-based applications, an analytical model is presented to achieve an optimal traffic split between terrestrial and satellite paths and optimal redundancy levels.
    • A Case Study on the Microstructure of Fibrous Peat (West Lake, China)

      Wilkinson, Stephen; Zhao, Chaofa; Yang, Zhongxuam; Kun, Pan (Springer, 2018-09-21)
      The classification of peat soils generates a very large number of different types, from a descriptive perspective this is useful, however such a system generates too many options for engineering purposes. The behaviour of organic soils varies based on the quantity and type of organic material present within the soil. The effects of fibre content are particularly important. The West Lake in Hangzhou has been dredged many times during its history to allow it to maintain its beauty. During the most recent dredging the sludge from the lake was transported via a 4km pipeline and deposited inside the Jiangyangfan Reservoir. The organic soil situated in Jiangyangfan Ecopark is a particularly interesting peaty material. The organic sludge was mixed and homogenised during the transportation process, and then would have settled out within the reservoir. This resulted in a more than 20m thick peat layer deposited with an uneven surface. The Ecopark buildings were then constructed on top of this in 2008. A combined electron microscope and mechanical study of the microstructure and behaviour of the peat has been used to identify the engineering impact of the presence of relatively small numbers of fibres within the soil matrix. The fibres within the peat modify its behaviour such that it can no longer be understood within the typical critical state framework for soils. The peat starts to plastically deform from very small levels of applied stress, in addition it does not display a tension cut-off failure, and ultimately fails in shear.
    • From collapsed coal mines to floating solar farms, why China's new power stations matter

      Pouran, Hamid (Elsevier, 2018-09-19)
      Inauguration of the world’s largest floating solar power plant on a collapsed coal mine exemplifies China's commitment to transition to a low carbon economy. This 70 MW project covers more than 63 ha of the flooded area and can provide electricity for 21,000 homes. It also demonstrates China's ambition to amend its fragile environmental status namely air pollution, which claims 1.6 million lives every year. Soon after the completion, many countries expressed interest in building similar power stations, and within few months some companies released innovative products tailored specifically for improving the efficiency of floating solar power plants. China has a unique capacity to implement new ideas, scale them up and commercialise efficiently and now its self-declared war on pollution in 2014 seems to be reshaping the world energy landscape. China's plan to build 1 GW floating solar farms on abandoned coal mines present a stark contrast to the current environmental policies of the government of the United States. The innovative thinking behind these projects suggests that not only this country is taking the lead in renewable energies, but it is moving beyond speed, efficiency and mass production, and becoming a hub for innovation in green energy technologies.
    • The implementation of stakeholder management and building information modelling (BIM) in UK construction projects

      Singh, Sukhtaj; Chinyio, Ezekiel; Suresh, Subashini (Association of Researchers in Construction Management, 2018-09-03)
      The implementation and usage of Building Information Modelling (BIM) on construction projects affects procurement and the supply chain activities. BIM process is changing the traditional modus operandi of the construction industry where many projects have failed to achieve its objectives due to ineffective stakeholder management. An on-going PhD study explores how to mitigate delays and conflicts between stakeholders on BIM implemented projects in the UK. This paper is based on critical literature review and primary data collection through semi-structured interviews. Findings from the literature review show that BIM publication such as PAS 1192-2:2013, Employers Information Requirements (EIR) and BIM Execution Plan (BEP) sets out clear requirements for the coordination and collaboration process for the BIM model production. This provides a huge potential to enhance and facilitate communication among stakeholders. This helps in mitigating conflicts among stakeholders. The findings from the interviewees shows that BIM can help project teams to proactively satisfy stakeholders by engaging them early on in the construction process and seek solutions to avoid or minimise delays and conflicts. The paper concludes that it has culture, trust, people, technology, communication and structures are at its core for managing stakeholders within BIM projects.
    • Cathepsin B-Sensitive and Biocompatible Dendritic polyHPMA-Gemcitabine Prodrug-Based Nanoscale System Markedly Enhances the Antitumor Activity

      Dai, Yan; Ma, Xuelei; Zhang, Yanhong; Chen, Kai; Tang, James Zhenggui; Gong, Qiyong; Luo, Kui (The Royal Society of Chemistry, 2018-09)
      To improve therapeutic indexes of gemcitabine (GEM), a stimuli-responsive dendritic polyHPMA copolymer conjugated with gemcitabine (Dendritic polyHPMA-GEM) prodrug was designed and synthesized via one-pot synthesis of RAFT polymerization. The prodrug with dendritic architectures is able to aggregate and form stable nanoscale system with a size of 46 nm. The dendritic prodrug with high molecular weight (HMW) of 168 kDa can biodegrade to low molecular weight (LMW, 29 kDa) segments for excretion. The prodrug demonstrates enzyme-responsive drug release features, and over 95% GEM was released from the carrier with the Cathepsin B within 3 h. The cellular mechanism of the dendritic prodrug was studied, suggesting the cytotoxicity is associated with the cell uptake and cell apoptosis. The prodrug shows good hemocompatibility and in vivo biosafety. Of interest, the dendritic polymer prodrug displays high accumulation within tumors, and markedly improves the in vivo antitumor activity against 4T1 murine breast cancer model compared to the free GEM. These in vivo antitumor activities are characterized as with markedly suppressed tumor volumes, indicating as the much higher tumor growth inhibition (TGI 83%) than that in GEM treatment (TGI, 36%), moreover some tumors are eliminated. The tumor xenograft immunohistochemistry study clearly indicates that the tumor apoptosis is through antiangiogenic effects. These results suggest that the stimuli-responsive dendritic polymer-gemcitabine has great potential as an efficient anticancer agent
    • The Microbial Production of Polyhydroxyalkanoates from Waste Polystyrene Fragments Attained Using Oxidative Degradation

      Johnston, Brian; Radecka, Iza; Hill, David; Chiellini, Emo; Ilieva, Vassilka Ivanova (MDPI, 2018-08-29)
      Excessive levels of plastic waste in our oceans and landfills indicate that there is an abundance of potential carbon sources with huge economic value being neglected. These waste plastics, through biological fermentation, could offer alternatives to traditional petrol-based plastics. Polyhydroxyalkanoates (PHAs) are a group of plastics produced by some strains of bacteria that could be part of a new generation of polyester materials that are biodegradable, biocompatible, and, most importantly, non-toxic if discarded. This study introduces the use of prodegraded high impact and general polystyrene (PS0). Polystyrene is commonly used in disposable cutlery, CD cases, trays, and packaging. Despite these applications, some forms of polystyrene PS remain financially and environmentally expensive to send to landfills. The prodegraded PS0 waste plastics used were broken down at varied high temperatures while exposed to ozone. These variables produced PS flakes (PS1–3) and a powder (PS4) with individual acid numbers. Consequently, after fermentation, different PHAs and amounts of biomass were produced. The bacterial strain, Cupriavidus necator H16, was selected for this study due to its well-documented genetic profile, stability, robustness, and ability to produce PHAs at relatively low temperatures. The accumulation of PHAs varied from 39% for prodegraded PS0 in nitrogen rich media to 48% (w/w) of dry biomass with the treated PS. The polymers extracted from biomass were analyzed using nuclear magnetic resonance (NMR) and electrospray ionization tandem mass spectrometry (ESI-MS/MS) to assess their molecular structure and properties. In conclusion, the PS0–3 specimens were shown to be the most promising carbon sources for PHA biosynthesis; with 3-hydroxybutyrate and up to 12 mol % of 3-hydroxyvalerate and 3-hydroxyhexanoate co-monomeric units generated.
    • Biomineralisation performance of bacteria isolated from a landfill in China

      Rajasekar, Adharsh; Wilkinson, Stephen; Sekar, Raju; Bridge, Jonathan; Medina-Roldán, Eduardo; K.S. Moy, Charles (2018-08-27)
      We report an investigation of microbially induced carbonate precipitation by seven indigenous bacteria isolated from a landfill in China. Bacterial strains were cultured in a medium supplemented with 25 mmol/L calcium chloride and 333 mmol/L urea. The experiments were carried out at 30 °C for 7 days with agitation by a shaking table at 130 r/min. Scanning electron microscopic and X-ray diffraction analyses showed variations in calcium carbonate polymorphs and mineral composition induced by all bacterial strains. The amount of carbonate precipitation was quantified by titration. The amount of carbonate precipitated in the medium varied among isolates, with the lowest being Bacillus aerius rawirorabr15 (LC092833) precipitating around 1.5 times more carbonate per unit volume than the abiotic (blank) solution. Pseudomonas nitroreducens szh_asesj15 (LC090854) was found to be the most efficient, precipitating 3.2 times more carbonate than the abiotic solution. Our results indicate that bacterial carbonate precipitation occurred through ureolysis and suggest that variations in carbonate crystal polymorphs and rates of precipitation were driven by strain-specific differences in urease expression and response to the alkaline environment. These results and the method applied provide benchmarking and screening data for assessing the bioremediation potential of indigenous bacteria for containment of contaminants in landfills.