Lipase Catalyzed Transesterification of Model Long-Chain Molecules in Double-Shell Cellulose-Coated Oil-in-Water Emulsion Particles as Microbioreactors

Lipase-catalyzed transesterification is prevalent in industrial production and is an effective alternative to chemical catalysis. However, due to lipases’ unique structure, the reaction requires a biphasic system, which suffers from a low reaction efficiency caused by a limited interfacial area. The use of emulsion particles was found to be an effective way to increase the surface area and activity. This research focuses on cellulose as a natural surfactant for oil-in-water emulsions and evaluates the ability of lipase, introduced into the emulsion’s aqueous phase, to integrate with the emulsion microparticles and catalyze the transesterification reaction of high molecular weight esters dissolved in the particles’ cores. Cellulose-coated emulsion particles’ morphology was investigated by light, fluorescence and cryogenic scanning electron microscopy, which reveal the complex emulsion structure. Lipase activity was evaluated by measuring the hydrolysis of emulsified p-nitrophenyl dodecanoate and by the transesterification of emulsified methyl laurate and oleyl alcohol dissolved in decane. Both experiments demonstrated that lipase introduced in the aqueous medium can penetrate the emulsion particles, localize at the inner oil core interface and perform effective catalysis. Furthermore, in this system, lipase successfully catalyzed a transesterification reaction rather than hydrolysis, despite the dominant presence of water.     

Constructing Mystery

In order to create an atmosphere, architecture and light must interact; they are intimately linked. As architects we consider light as a mysterious substance, about which we are not necessarily experts. This paper presents a pedagogy to teach the construction of such mystery, while understanding the physical and phenomenological mechanisms at play and the literary dimensions they hold. By constructing light installations students learn to design immersive environments that test various theses on projection.     

On tandem stochastic networks with time-deteriorating product quality

We consider an n-site tandem stochastic production network where each product moves sequentially through the sites, and the product's quality deteriorates with its sojourn time in the system. At each site the product goes through two stages: the first stage is a processing operation with a generally-distributed random duration. This operation either does or does not conclude successfully; in the latter case, the operation is repeated immediately. Once the processing operation concludes successfully, the product goes through an inspection stage lasting a generally-distributed random duration. At the end of the inspection the product's state is determined as follows: either (i) it requires additional processing and moves forward to the next site; or (ii) it is found ‘good’ and exits the network with quality value depending on its total sojourn time in the system; or (iii) it is declared ‘failed’, discarded, and exits the network with zero quality value. Two scenarios are analysed: (i) a new product enters the system only after the preceding product has exited and (ii) the network is a tandem Jackson-type system. For each scenario, we construct both time-dependent and quality-dependent performance measures. In the case where the sites can be arranged in an arbitrary order, we derive easy to implement optimal index-type policies of ordering the sites so as to maximise the quality rate of the production network.     

Bio-based blends from poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and natural rubber for packaging applications

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a promising bioplastic but has limited packaging applications due to its brittleness and poor processability. Incorporation of highly viscous high-molecular-weight natural rubber (HMW-NR, gel extracted from NR) into PHBV can improve these properties. HMW-NR is not commercially available, impeding commercialization of the PHBV/rubber blends. Therefore, an organic peroxide was used to selectively crosslink NR to increase its viscosity during its melt blending with PHBV. The PHBV/NR blends were fabricated through a two-step extrusion process using a twin-screw extruder. The blends contained two phases with crosslinked rubber being dispersed in PHBV, and had clear rubber loading-dependent differences in performance. The thermal stability and melt strength of the blends were enhanced over pristine PHBV, indicating improved processability. The flexibility and toughness of the blends were improved by 59 and 20%, respectively, compared with pristine PHBV, and were comparable to commercial petroleum-based plastics. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47334.     

Development of Gluten-Free Muffins made from Breadfruit and Unripe Plantain Flours

Inclusion of breadfruit (BF) and unripe plantain (UP) in gluten-free muffins was investigated along with a 1:1 BF/UP blend muffin and compared to controls made with gluten-free rice (RI) or traditional wheat (WH) flour. The alternative flours had a 10% higher fibre content than WH and 2%–4% higher than RI flours. Muffin batter viscosity of RI and WH was initially much lower (3-10 times) than UP, BF and BF/UP blend batter. Additionally, starch gelatinisation temperature was increased by 4%–14% for batter made from BF or UP flours, which can provide structural benefits to baked muffins. Muffins made with BF/UP were the hardest (34.7N), followed by BF (31.7N) and RI muffins (30.7N), with UP (28.4) and WH muffins (26.9N) being the softest. Interestingly, overall acceptability of gluten-free muffins showed that both BF/UP and BF flour muffins scored significantly higher than UP and RI muffins indicating their commercial potential.     

Performance of UV disinfection and the microbial quality of greywater effluent along a reuse system for toilet flushing

This paper examines the microbial quality of treated RBC (Rotating Biological Contactor) and MBR (Membrane Bioreactor) light greywater along a continuous pilot-scale reuse system for toilet flushing, quantifies the efficiency of UV disinfection unit, and evaluates the regrowth potential of selected microorganisms along the system. The UV disinfection unit was found to be very efficient in reducing faecal coliforms and Staphylococcus aureus. On the other hand, its efficiency of inactivation of HPC (Heterotrophic Plate Count) and Pseudomonas aeruginosa was lower. Some regrowth occurred in the reuse system as a result of HPC regrowth which included opportunistic pathogens such as P. aeruginosa. Although the membrane (UF) of the MBR system removed all bacteria from the greywater, bacteria were observed in the reuse system due to “hopping phenomenon.” The microbial quality of the disinfected greywater was found to be equal or even better than the microbial quality of “clean” water in toilet bowls flushed with potable water (and used for excretion). Thus, the added health risk associated with reusing the UV-disinfected greywater for toilet flushing (regarding P. aeruginosa and S. aureus), was found to be insignificant. The UV disinfection unit totally removed (100%) the viral indicator (F-RNA phage, host: E. coli F_amp⁺) injected to the treatment systems simulating transient viral contamination. To conclude, this work contributes to better design of UV disinfection reactors and provides an insight into the long-term behavior of selected microorganisms along on-site greywater reuse systems for toilet flushing.     

Microwave drilling of bones

This paper presents a feasibility study of drilling in fresh wet bone tissue in vitro using the microwave drill method [Jerby et al, 2002], toward testing its applicability in orthopaedic surgery. The microwave drill uses a near-field focused energy (typically, power under approximately 200 W at 2.45-GHz frequency) in order to penetrate bone in a drilling speed of approximately 1 mm/s. The effect of microwave drilling on mechanical properties of whole ovine tibial and chicken femoral bones drilled in vitro was studied using three-point-bending strength and fatigue tests. Properties were compared to those of geometrically similar bones that were equivalently drilled using the currently accepted mechanical rotary drilling method. Strength of mid-shaft, elastic moduli, and cycles to failure in fatigue were statistically indistinguishable between specimen groups assigned for microwave and mechanical drilling. Carbonized margins around the microwave-drilled hole were approximately 15% the hole diameter. Optical and scanning electron microscopy studies showed that the microwave drill produces substantially smoother holes in cortical bone than those produced by a mechanical drill. The hot spot produced by the microwave drill has the potential for overcoming two major problems presently associated with mechanical drilling in cortical and trabecular bone during orthopaedic surgeries: formation of debris and rupture of bone vasculature during drilling.     

Optical traps with geometric aberrations

We assess the influence of geometric aberrations on the in-plane performance of optical traps by studying the dynamics of trapped colloidal spheres in deliberately distorted holographic optical tweezers. The lateral stiffness of the traps turns out to be insensitive to moderate amounts of coma, astigmatism, and spherical aberration. Moreover holographic aberration correction enables us to compensate inherent shortcomings in the optical train, thereby adaptively improving its performance. We also demonstrate the effects of geometric aberrations on the intensity profiles of optical vortices, whose readily measured deformations suggest a method for rapidly estimating and correcting geometric aberrations in holographic trapping systems.     

Genetic diversity of the human pathogen Vibrio vulnificus: a new phylogroup

The biotype 3 group of the human pathogen Vibrio vulnificus emerged in Israel probably as a result of genome hybridization of two bacterial populations. We performed a genomic and phylogenetic study of V. vulnificus strains isolated from the environmental niche from which this group emerged — fish aquaculture in Israel. The genetic relationships and evolutionary aspects of 188 environmental and clinical isolates of the bacterium were studied by genomic typing. Genetic relations were determined based on variation at 12 variable number tandem repeat (VNTR, also termed SSR) loci. Analysis revealed a new cluster, in addition to the main groups of biotype 1& 2 and biotype 3. Similar grouping results were obtained with three different statistical approaches. Isolates forming this new cluster presented unclear biochemical profile nevertheless were not identified as biotype 1 or biotype 3. Further examination of representative strains by multilocus sequence typing (MLST) of 10 housekeeping genes and 5 conserved hypothetical genes supported the identification of this as yet undiscovered phylogroup (phenotypically diverse), termed clade A herein. This new clonal subgroup includes environmental as well as clinical isolates. The results highlight the fish aquaculture environment, and possibly man-made ecological niches as a whole, as a source for the emergence of new pathogenic strains.