Characterization of a Bioflocculant (MBF-UFH) Produced by Bacillus sp. AEMREG7

A bioflocculant named MBF-UFH produced by a Bacillus species isolated from sediment samples of Algoa Bay of the Eastern Cape Province of South Africa was characterized. The bacterial identification was through 16S rDNA sequencing; nucleotide sequences were deposited in GenBank as Bacillus sp. AEMREG7 with Accession Number {"type":"entrez-nucleotide","attrs":{"text":"KP659187","term_id":"768700521","term_text":"KP659187"}}KP659187. The production of the bioflocculant was observed to be closely associated with cell growth. The bioflocculant had the highest flocculating activity of 83.2% after 72 h of cultivation, and approximately 1.6 g of purified MBF-UFH was recovered from 1 L of fermentation broth. Its chemical analyses indicated that it is a glycoprotein composed of polysaccharide (76%) and protein (14%). Fourier transform infrared spectroscopy (FTIR) revealed that it consisted of hydroxyl, amide, carboxyl and methoxyl as the functional moieties. Scanning electron microscopy (SEM) revealed the amorphous structure of MBF-UFH and flocculated kaolin clay particles. The maximum flocculating activity of 92.6% against kaolin clay suspension was achieved at 0.3 mg/mL over pH ranges of 3–11 with the peak flocculating rate at pH 8 in the presence of MgCl₂. The bioflocculant retained high flocculating activity of 90% after heating at 100 °C for 1 h. MBF-UFH appears to have immense potential as an alternative to conventional chemical flocculants.     

Exploring routes to stabilize a cationic pyridoxamine in an artificial transaminase: site-directed mutagenesis versus synthetic cofactors

Two artificial transaminases were assembled by linking a pyridoxaminederivative within an engineered fatty acid binding protein.The goal of mimicking a native transamination site by stabilizinga cationic pyridoxamine ring system was approached using twodifferent strategies. First, the scaffold of intestinal fattyacid binding protein (IFABP) was tailored by molecular modelingand site-directed mutagenesis to position a carboxylate groupclose to the pyridine nitrogen of the cofactor. When these IFABPmutants (IFABP-V60C/L38K/E93E and -V60C/E51K/E93E) proved tobe unstable, a second approach was explored. By N-methylationof the pyridoxamine, a cationic cofactor was created and tetheredto Cys60 of IFABP-V60C/L38K and -V60C/E51K; this latter strategyhad the effect of permanently installing a positive charge onthe cofactor. These chemogenetic assemblies catalyze the transaminationbetween -ketoglutarate and various amino acids with enantioselectivitiesof up to 96% ee. The pH profile of the initial rates is bellshaped and similar to native aminotransferases. The k_cat valuesand the turnover numbers for these new constructs are the highestachieved to date in our system. This success was only made possibleby the unique flexibility of the underlying enzyme design conceptemployed, which permits full control of both the protein scaffoldand the catalytically active group.     

USE OF X-RAY MICROTOMOGRAPHY TO FOLLOW THE CONVECTIVE HEAT DRYING OF WASTEWATER SLUDGES

X-ray microtomography is proposed as a new tool to investigate the evolution of size, shape and texture of soft materials during a drying operation. This study is focused on the drying of mechanically dewatered sludges from a secondary wastewater treatment. The shrinkage phenomenon is shown to play a crucial role in the control of the drying process. The shrinkage curves are determined by analysing the shape and size of cross sectional microtomographic images of sludge extrudates at different levels of drying. The observation of drying and shrinkage curves allows us to determine 3 critical water content values, which define different drying zones where extragranular, intragranular or mixed limitations prevail. When drying is externally controlled, the decrease of the drying rate observed during experiments can be related to the reduction of the external area of the sample, i.e., to shrinkage. When drying is internally controlled, resistances inside the solid govern the process. Between these two extreme situations, the drying rate reduction is the result of both the external area decrease and the development of internal resistances limiting drying. A multizone model is proposed to describe quantitatively these observations. The analysis of the internal texture of the sludge extrudates reveals crack formation at the end of the drying process. The onset of crack formation is clearly related to the appearance of internal transfer limitations, i.e., humidity and temperature gradients inside the material.     

Analysis of the Reactive Element Effect on the Oxidation of Ceria Doped Nickel

The effects of external doping with CeO₂ on the oxidation of nickel have been evaluated. The materials studied were pure Ni and Ni with the surface doped with CeO₂ by pulsed laser deposition. The oxidation kinetics were measured using thermogravimetric analysis. The oxidation microstructures were observed by scanning electron microscopy and cross-sectional transmission electron microscopy. Compositional analysis was performed with energy dispersive X-ray analysis and sputtering neutrals mass spectrometry. Phase identification was performed using X-ray diffraction. Doping with CeO₂ resulted in a significant decrease in the NiO growth rate at intermediate temperatures, e.g. 800?°C. The scales on doped Ni grew primarily inward whereas those on the undoped Ni grew primarily outward. Deposition of the CeO₂ dopant onto Ni with a thin, preformed NiO layer produced a similar reduction in the subsequent NiO growth rate. The CeO₂ dopant did not reduce the growth rate at high temperature (1,300?°C). The results indicate that the CeO₂ dopant influences grain boundary transport in the NiO. Mechanisms are presented to attempt to describe the above observations.     

Studies of the microstructure of polymer-modified bitumen emulsions using confocal laser scanning microscopy

Polymer-modified bitumen emulsions present a safer and more environmentally friendly binder for enhancing the properties of roads. Cationic bitumen emulsion binders containing polymer latex were investigated using confocal laser scanning microscopy. The latex was incorporated into the bitumen emulsion by using four different addition methods and all emulsions were processed with a conventional colloid mill. The emulsion binder films were studied after evaporation of the emulsion aqueous phase. We show how the microstructure and distribution of the polymer varies within the bitumen binder depending on latex addition method, and that the microstructure of the binder remains intact when exposed to elevated temperature. It was found that a distinctly fine dispersion of polymer results when the polymer is blended into the bitumen before the emulsifying process (a monophase emulsion). In contrast, bi-phase emulsion binders produced by either post-adding the latex to the bitumen emulsion, or by adding the latex into the emulsifier solution phase before processing, or by comilling the latex with the bitumen, water and emulsifier all resulted in a network formation of bitumen particles surrounded by a continuous polymer film. The use of emulsified binders appears to result in a more evenly distributed polymer network compared to the use of hot polymer-modified binders, and they therefore have greater potential for consistent binder cohesion strength, stone retention and therefore improved pavement performance.     

An Innovative Approach for Using the GRAI Methodology for Reengineering the New Product Introduction Process

This paper represents the culmination of a four-year ethnographic research project in a leading U.K. manufacturing company. A number of organizational deficiencies in the new product introduction (NPI) process are identified. Proposals subsequently are implemented that enhance the effectiveness of this process. The paper identifies the critical need for organizations to communicate effectively among different functional areas with respect to new products. A review of modeling techniques identifies the GRAI grid as an effective model for analyzing and improving cooperative business processes. The GRAI grid is set within the framework of a novel implementation methodology and subsequently is applied to the NPI process within the collaborating company. The paper concludes by reporting the substantial benefits gained.     

Inhibition of cytolytic T lymphocyte activity by oxysterols

The objective of this study was to investigate the effects of oxysterols (OS), namely 5α-hydroxy-6-ketocholestanol, 6-ketocholestanol and 25-hydroxycholesterol, on specific cell-mediated cytotoxicity by C57BL/6 spleen cells against P815-X2 (a DBA/2 mastocytoma) target cells. Cytolytic T lymphocytes (CTL) were generated by intraperitoneally injecting C57BL/6 mice with P815-X2 tumor cells 10 d prior to the cytotoxicity experiments. Preincubation of CTL with 10⁻⁵ M 5α-hydroxy-6-ketocholestanol and 6-ketocholestanol for 45 min in lipoprotein-depleted medium resulted in an inhibition of cytolytic activity (73 and 43%, respectively) as measured by 4-h⁵¹Cr release. At a concentration of 5×10⁻⁶ M, 5α-hydroxy-6-ketocholestanol inhibited CTL activity by 65%, whereas 6-ketocholestanol did not elicit any inhibition. By contrast, 25-hydroxycholesterol did not inhibit CTL at either concentration, although it is known to be a potent inhibitor of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, the rate-limiting enzyme in the cholesterol biosynthetic pathway. When CTL were preincubated with OS in lipoprotein-replete medium, there was no inhibition of CTL activity at the respective concentrations. The results suggest that the inhibition of CTL activity upon short-term incubation with OS is not due to the inhibition of cholesterol synthesis, but may be due to the insertion of OS into the plasma membrane to replace cholesterol and alteration of membrane physical properties.     

Comparing digital light processing and stereolithography vat polymerization Technologies for antimicrobial 3D printing using silver oxide as an antimicrobial filler

Vat polymerization technology allows filler particles to be incorporated into photosensitive 3D printing resin to improve the properties of the printed material. This method can be used to produce medical devices with an antimicrobial effect that can reduce biofilm formation and reduce infections due to indwelling devices. Metal oxides have the potential to combat antibiotic-resistant bacteria, further lowering the risk of hospital-acquired infections. The antimicrobial agent in this study, silver oxide, was evaluated for its antimicrobial effect against gram-positive bacteria (Staphylococcus epidermidis) as these are the main cause of biofilm formation. The 3D printed samples demonstrated a strong antimicrobial effect at low concentrations of 1 wt.%. Two vat polymerization technologies, stereolithography (SLA) and digital light processing (DLP), were compared for their suitability for producing 3D printed samples with an antimicrobial effect. DLP successfully produced samples with mechanical properties comparable to the base resin, whereas SLA samples had reduced mechanical strength at higher concentrations of silver oxide filler. Neither printing technology nor silver oxide concentration had a statistically significant effect on the mechanical properties of the printed materials.     

Distributed interactive communication in simulated space-dwelling groups

This report describes the development and preliminary application of an experimental test bed for modeling human behavior in the context of a computer generated environment to analyze the effects of variations in communication modalities, incentives and stressful conditions. In addition to detailing the methodological development of a simulated task environment that provides for electronic monitoring and recording of individual and group behavior, the initial substantive findings from an experimental analysis of distributed interactive communication in simulated space dwelling groups are described. Crews of three members each (male and female) participated in simulated "planetary missions" based upon a synthetic scenario task that required identification, collection, and analysis of geologic specimens with a range of grade values. The results of these preliminary studies showed clearly that cooperative and productive interactions were maintained between individually isolated and distributed individuals communicating and problem-solving effectively in a computer-generated "planetary" environment over extended time intervals without benefit of one another's physical presence. Studies on communication channel constraints confirmed the functional interchangeability between available modalities with the highest degree of interchangeability occurring between Audio and Text modes of communication. The effects of task-related incentives were determined by the conditions under which they were available with Positive Incentives effectively attenuating decrements in performance under stressful time pressure.