Faculty of Science and Agriculture

The Escherichia coli phytase gene appA encoding enzyme AppA was cloned in a broad host range plasmid pBBR1MCS2 (lac promoter), termed pVA1, and transformed into the Ensifer meliloti 1020. Transformation of pVA1 in Ensifer meliloti {E. m (pVA1)} increased its phosphatase and phytase activity by ∼9-and ∼50-fold, respectively, compared to the transformants containing empty plasmid as control {E. m (pBBR1MCS2)}. The western blot experiments using rabbit anti-AppA antibody showed that AppA is translocated into the periplasm of the host after its expression. Ensifer meliloti harboring AppA protein {E. m (pVA1)} and {E. m (pBBR1MCS2)} could acidify the unbuffered phytate minimal media (pH 8.0) containing Ca-phytate or Na-phytate as sole organic P (Po) source to below pH 5.0 and released P. However, both {E. m (pVA1)} and {E. m (pBBR1MCS2)} neither dropped pH of the medium nor released P when the medium was buffered at pH 8.0 using Tris–Cl, indicating that acidification of medium was important for the enzymatic hydrolysis of phytate. Further experiments proved that maize plants inoculated with {E. m. (pVA1)} showed increase in growth under sterile semi solid agar (SSA) medium containing Na-phytate as sole P source. The present study could be helpful in generating better transgenic bioinoculants harboring phosphate mineralization properties that ultimately promote plant growth.

Human immunodeficiency virus (HIV) infections in sub-Saharan Africa represent about 56% of global infections. Many studies have targeted HIV-1 protease for the development of drugs against AIDS. Re-combinant HIV-1 protease is used to screen new drugs from synthetic compounds or natural substances. Along with the wild type (C-SA) we also over-expressed and characterized two mutant forms from patients that had shown resistance to protease inhibitors. Using recombinant DNA technology, we constructed three recombinant plasmids in pGEX-6P-1 and expressed them containing a sequence encoding wild type HIV protease and two mutants (I36T[T contains 100 amino acids and L38L[N[L contains 101 amino acids). These recombinant proteins were isolated from inclusion bodies by using QFF anion exchange and GST trap columns. In SDSePAGE, we obtained these HIV proteases as single bands of approximately 11.5, 11.6 and 11.7 kDa for the wild type, I36T[Tand L38L[N[L mutants, respectively. The enzyme was recovered efficiently (0.25 mg protein/L of Escherichia coli culture) and had high specific activity of 2.02, 2.20 and 1.33 mmol min À1 mg À1 at an optimal pH of 5 and temperature of 37 C for the wild type, I36T[T and L38L[N[L, respectively. The method employed here provides an easy and rapid purification of the HIV-1(C-SA) protease from the inclusion bodies, with high yield and high specific activities.

An extracellular endoinulinase from Xanthomonas campestris pv. phaseoli KM 24 mutant was purifi ed to homogeneity by gel fi ltration chromatography and showed a specifi c activity of 119 U/mg. The optimum pH and temperature of the purifi ed enzyme were found to
be 6.0 and 50 °C, respectively. The enzyme was stable up to 60 °C, retaining 60 % of residual activity for 30 min, but inactivated rapidly above 60 °C. The enzyme was found to be stable at pH=6–9 when it retained 100 % of its residual activity. The Lineweaver-Burk plot
showed that the apparent Km and vmax values of the inulinase when using inulin as a substrate were 1.15 mg/mL and 0.15 μM/min, respectively, whereas the kcat value was found to be 0.145 min–1. The calculated catalytic effi ciency of the enzyme was found to be 0.126
(mg·min)/mL. The purifi ed inulinase can be used in the production of high fructose syrups.

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Summary Effect of the metabolic load caused by the presence of plasmids on mineral phosphate-solubilizing (MPS) Enterobacter asburiae PSI3, was monitored with four plasmid cloning vectors and one native plasmid, varying in size, nature of the replicon, copy number and antibiotic resistance genes. Except for one plasmid, the presence of all other plasmids in E. asburiae PSI3 resulted in the loss of the MPS phenotype as reflected by the failure to bring about a drop in pH and release soluble P when grown in media containing rock phosphate (RP) as the sole P source. When 100 mM soluble P was supplemented along with RP, the adverse effects of plasmids on MPS phenotype and on growth parameters was reduced for some plasmid bearing derivatives, as monitored in terms of specific growth rates, glucose consumed, gluconic acids yields and P released. When 10 mM of soluble P as the only P source, was added to the medium all transformants showed growth and pH drop comparable with native strain. It may be concluded that different plasmids impose, to varying extents, a metabolic load in the phosphate-solubilizing bacterium E. asburiae PSI3 and results in diminishing its growth and P-solubilizing ability in P deficient conditions.

Herein, we synthesized three nickel(II) dithiophosphonate complexes of the type [Ni{S2P(OR)(4-C6H4OMe)}2] [Me = Methyl; R = H (1), C3H7 (2)] and [Ni{S2P(OR)(4-C6H4OEt}2] [Et = Ethyl; R = (C6H5)2CH (3)], their structures confirmed by single crystal X-ray studies. These complexes were subjected to surfactant/solvent reactions at 300 ºC for one hour as flexible molecular precursors to prepare either nickel sulfide or nickel phosphide particles. The decomposition of complex 2 in TOPO/ODE, TOPO/TOP, HDA/TOP and HDA/ODE yielded hexagonal NiS, Ni2P, Ni5P4 and rhombohedral NiS, respectively. Similarly, the decomposition of complex 1 in TOPO/TOP and HDA/TOP yielded hexagonal Ni2P and Ni5P4 and that of complex 3 in similar solvents led to hexagonal Ni5P4, with TOP as the likely phosphorus provider. Hexagonal NiS was prepared from the solvent-less decomposition of complexes 1 and 2 at 400 ºC. NiS (rhom) had the best specific supercapacitance of 2304 F/g at 2 mV/s scan rate followed by 1672F/g of Ni2P (hex). Similarly, NiS (rhom) and Ni2P (hex) showed the highest power and energy densities of 7.4 kW/kg, 54.16W/kg, 6.3kW/kg and 44.7W/kg, respectively. Ni5P4 (hex) had the lowest recorded overpotential of 350 mV at a current density of 50 mA/cm 2 among the samples tested for the oxygen evolution reaction (OER). NiS (hex) and Ni5P4 (hex) had the lowest overpotentials of 231 and 235 mV to achieve a current density of 50 mA/cm 2 , respectively, in hydrogen evolution reaction(HER) examinations.

Straightforward synthetic routes to the preparation of transition metal phosphides or their chalcogenide analogues are highly desired due to their widespread applications, including catalysis. We report a facile and simple route for the preparation of a pure phase nickel phosphide (Ni 2 P) and phase transformations in the nickel sulfide (NiS) system through a solvent-less synthetic protocol. Decomposition of different sulfur-based complexes (dithiocarbamate, xanthate, and dithiophosphonate) of nickel(II) was investigated in the presence and absence of triphenylphosphine (TPP). The optimization of reaction parameters (nature of precursor, ratio of TPP, temperature, and time) indicated that phosphorus-and sulfur-containing inorganic dithiophosphonate complexes and TPP (1:1 mole ratio) produced pure nickel phosphide, whereas different phases of nickel sulfide were obtained from dithiocarbamate and xanthate precursors in the presence or absence of TPP. A plausible explanation of the sulfide or phosphide phase formation is suggested, and the performance of Ni 2 P was investigated as an electrocatalyst for supercapacitance and overall water-splitting reactions. The performance of Ni 2 P with the surface free of any capping agents is not well explored, as common synthetic methods are solution-based routes; therefore, the electrocatalytic performance was also compared with metal phosphides, prepared by other routes. The highest specific capacitance of 367 F/g was observed at 1 A/g, and the maximum energy and power density of Ni 2 P were calculated to be 17.9 Wh/kg and 6951 W/kg, respectively. The prepared nickel phosphide required overpotentials of 174 and 316 mV along with Tafel slopes of 115 and 95 mV/dec to achieve a current density of 10 mA/cm 2 for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively.

Cost-effective and readily available catalysts applicable for electrochemical conversion technologies are highly desired. Herein, we report the synthesis of dithiophosphonate complexes of the type [Ni{S 2 P(OH) (4-CH 3 OC 6 H 4)} 2 ] (1), [Co{S 2 P(OC 4 H 9)(4-CH 3 OC 6 H 4)} 3 ] (2) and [Fe{S 2 P(OH)(4-CH 3 OC 6 H 4)} 3 ] (3) and employed them to prepare Ni 2 P, Co-Ni 2 P and Fe-Ni 2 P nanoparticles. Ni 2 P was formed by a facile hot injection method by decomposing complex 1 in tri-octylphosphine oxide/tri-n-octylphosphine at 300°C. The prepared Ni 2 P was doped with Co and Fe employing complexes 2 and 3, respectively, under similar experimental conditions. Doping Ni 2 P with Co and Fe demonstrated synergistic improvement of Ni 2 P performance as an electrocatalyst in supercapcitance, hydrogen evololution and oxygen evolution reactions in alkaline medium. Cobalt doping improved the Ni 2 P charge storage capacity with a supercapacitance of 864 F g −1 at 1 A g −1 current density. Fe doped Ni 2 P recorded the lowest overpotential of 259 mV to achieve a current density of 10 mA cm −2 and a Tafel slope of 80 mV dec −1 for OER, better than the undoped Ni 2 P and the benchmark IrO 2. Likewise, Fe-doped Ni 2 P electrode required the lowest overpotential of 68 mV with a Tafel slope of 110 mV dec −1 to attain the same current density for HER. All catalysts showed excellent stability in supercapacitance and overall water splitting reactions, indicating their practical use in energy conversion technologies. † Electronic supplementary information (ESI) available: TGA of complexes, UVvis absorption spectra, SEM, TEM, HRTEM and XPS images of nano-materials and comparison tables. See

Ni, Co and Fe dithiophosphonate complexes were synthesized to prepare pristine Ni2P, Co-Ni2P and Fe-Ni2P nanoparticles. The potential of synthesized materials was tested for supercapacitance and overall water splitting and the materials showed excellent activity.