Characterization of a newly isolated Rubrivivax benzoatilyticus PS-5 with self-flocculation property and optimization pathway for 5-aminolevulinic acid production

Six strains of phototrophic purple non-sulfur bacteria were isolated from paddy soil, lake water and pond sediment samples. They showed the ability to produce 5-aminolevulinic acid under anaerobic-light (3,000 lux) condition. A selected strain, designated as PS-5, produced the highest 5-aminolevulinic acid (ALA) concentration (45.10 μM) and productivity (0.94 μ M h-1) in glutamate-malate (GM) medium as well as possessed self-flocculating ability. Based on physiological and 16S rRNA sequence, the isolate PS-5 was identified to be Rubrivivax benzoatilyticus. The optimum concentration of C4 pathway precursors was 7.5 mM glycine and 10 mM succinate with supplementation of 10 mM levulinic acid. This resulted in 4.2 fold increase of 5-aminolevulinic acid production to 190.74 μM and 2.7-fold increase of its productivity to 2.57 μM h-1 compared to the control. In addition, the optimum concentration of C5 pathway precursor was 50 mM glutamate with the maximum 5-aminolevulinic acid production of 84.12 μM and productivity of 1.56 μM h-1. Therefore, R. benzoatilyticus PS-5 could produce 5-aminolevulinic acid using both C4 and C5 pathway precursors and preferred C4 pathway over C5 pathway as it produced more than 2.3 folds higher 5-aminolevulinic acid concentration.Keywords: 5-Aminolevulinic acid, photosynthetic bacteria, self-flocculation, optimization, Rubrivivax benzoatilyticusAfrican Journal of Biotechnology Vol. 12(16), pp. 2069-208

Highly Efficient Catalytic Microengines: Template Electrosynthesis of Polyaniline/Platinum Microtubes

Highly efficient catalytic microtubular engines are synthesized rapidly and inexpensively using an electrochemical growth of bilayer polyaniline/platinum microtubes within the conically shaped pores of a polycarbonate template membrane. These mass-produced microtubular engines are only 8 μm long, are self-propelled at an ultrafast speed (of over 350 body lengths s^(–1)), and can operate in very low levels of the hydrogen peroxide fuel (down to 0.2%). The propulsion characteristics and optimization of these microtubular engines are described, along with their efficient operation in different biological environments which holds great promise for biomedical applications

Efficient bubble propulsion of polymer-based microengines in real-life environments

Template-electrodeposited polymer/Pt microtube engines display efficient propulsion in a wide range of real-life samples ranging from seawater to human serum. Remarkably high speeds are observed in fuel-enhanced raw serum, apple juice, seawater, lake and river water samples. Our results indicate that polymer-based microengines hold considerable promise for diverse practical applications and that real samples exert different effects upon propulsion of different bubble-propelled microtube engines

Hybrid Nanomotor: A Catalytically/Magnetically Powered Adaptive Nanowire Swimmer

A synthetic hybrid nanomotor, which combines chemically powered propulsion and magnetically driven locomotion, is described. The new catalytic–magnetic nanomotor consists of a flexible multisegment Pt-Au-Agflex-Ni nanowire, with the Pt-Au and Au-Agflex-Ni portions responsible for the catalytic and magnetic propulsion modes, respectively. The experimental data and theoretical considerations indicate that the hybrid design only minimally compromises the individual propulsion modes. Rapid and convenient switching from the catalytic to the magnetic mode is illustrated. The resulting catalytic–magnetic adaptive nanomotor can address the fuel depletion and salt limitation common to chemically powered motors by switching to magnetic propulsion. Reversal of the motion direction is also achieved upon applying the magnetic field. Such use of two sources to power a hybrid device offers a broader scope of operation and holds considerable promise for designing adaptive nanovehicles that reconfigure their operation in response to environmental changes or unexpected events

Enhance 1,3-propanediol production from crude glycerol in batch and fed-batch fermentation with two-phase pH-controlled strategy

The batch fermentation of 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae SU6 at different crude glycerol concentration (40-100 g l-1), pH (6.5-7.5) and temperature (31-40\ubaC) combined with two-phase pH-controlled strategy was investigated. Effect of feeding rate (0.10-0.15 L h-1) was studied in fed-batch fermentation. In batch fermentation, the optimal condition was 60 g l-1 crude glycerol, pH control at 6.5 and cultivation temperature at 37\ubaC. The maximum 1,3-PD of 20 g l-1, the yield of 0.34 g 1,3-PD g-1 glycerol consumed and the productivity of 1.25 g l-1 h-1 were achieved at 16 hrs cultivation. The by-products were acetic acid and succinic acid at 2.7 and 1.1 g l-1, respectively. Two-phase pH-controlled strategy gave better results (24.95 g l-1 1,3-PD and 1.78 g l-1 h-1 productivity) than constant pH-controlled strategy (20 g l-1 and 1.25 g l-1 h-1, respectively) at 16 hrs incubation. In fed-batch fermentation, the maximum 1,3-PD of 45.35 g l-1 was achieved at constant feeding rate of 0.1 L h-1. The yield and productivity were 0.44 g g-1 and 1.94 g l-1 h-1, respectively. The fed-batch fermentation with constant feeding at 0.1 L h-1 with two-phase pH-controlled strategy gave 2.2 folds higher 1,3 PD concentration than the batch fermentation with two-phase pH-controlled strategy. This demonstrated the great impact of combination of pH control and feeding strategies in fed-batch fermentation on enhancing 1,3-propanediol production

Examining Biased Assimilation of Brand-related Online Reviews

This paper examines the impact of pre-existing brand attitudes on consumer processing of electronic word-of-mouth (eWOM). This topic is particularly important for brands that simultaneously possess strongly pronounced proponents as well as opponents. Two experimental studies using univalent (study 1, N = 538) and mixed (study 2, N = 262) sets of online reviews find indications for biased assimilation effects of eWOM processing. Consumers perceive positive (negative) arguments in online reviews as more (less) persuasive when having a positive (negative) attitude towards the brand. Perceived persuasiveness in turn influences behavioral intentions and acts as a mediator on the relationship between attitude and behavioral intentions. We examine two moderators of this effect. When priming individuals to focus on other consumers (vs. a self-focus prime), the biased assimilation effect is weaker (study 3a, N = 131). In contrast, we show that biased assimilation becomes stronger under conditions of high (vs. low) cognitive impairment (study 3b, N = 124). Our findings contribute to the literature on the relationship between eWOM and brands and advance our understanding of potential outcomes of brand polarization

Highly Efficient Catalytic Microengines: Template Electrosynthesis of Polyaniline/Platinum Microtubes

Highly efficient catalytic microtubular engines are synthesized rapidly and inexpensively using an electrochemical growth of bilayer polyaniline/platinum microtubes within the conically shaped pores of a polycarbonate template membrane. These mass-produced microtubular engines are only 8 μm long, are self-propelled at an ultrafast speed (of over 350 body lengths s^(–1)), and can operate in very low levels of the hydrogen peroxide fuel (down to 0.2%). The propulsion characteristics and optimization of these microtubular engines are described, along with their efficient operation in different biological environments which holds great promise for biomedical applications

Hybrid Nanomotor: A Catalytically/Magnetically Powered Adaptive Nanowire Swimmer

A synthetic hybrid nanomotor, which combines chemically powered propulsion and magnetically driven locomotion, is described. The new catalytic–magnetic nanomotor consists of a flexible multisegment Pt-Au-Agflex-Ni nanowire, with the Pt-Au and Au-Agflex-Ni portions responsible for the catalytic and magnetic propulsion modes, respectively. The experimental data and theoretical considerations indicate that the hybrid design only minimally compromises the individual propulsion modes. Rapid and convenient switching from the catalytic to the magnetic mode is illustrated. The resulting catalytic–magnetic adaptive nanomotor can address the fuel depletion and salt limitation common to chemically powered motors by switching to magnetic propulsion. Reversal of the motion direction is also achieved upon applying the magnetic field. Such use of two sources to power a hybrid device offers a broader scope of operation and holds considerable promise for designing adaptive nanovehicles that reconfigure their operation in response to environmental changes or unexpected events

Magnetically Powered Flexible Metal Nanowire Motors

Fuel-free magnetically driven propulsion of flexible Au/Ag/Ni nanowires, with a gold ‘head’ and nickel ‘tail’, linked by a partially dissolved and weakened silver bridge, is described. The flexible bridge facilitates the cyclic mechanical deformations under an external rotating magnetic field. Under such a field the nickel segment starts to rotate, facilitating the rotation of the gold segment at a different amplitude, hence breaking the system symmetry and inducing the movement. Forward (‘pushing’) and backward (‘pulling’) magnetically powered locomotion and a precise On/Off motion control are achieved by tailoring the length of the nickel and gold segments and modulating the magnetic field, respectively. Efficient locomotion in urine samples and in high-salt media is illustrated. The new magnetic nanowire swimmers can be prepared in large scale using a simple template electrodeposition protocol and offer considerable promise for diverse practical applications