Efficient conversion of d-glucose into d-sorbitol over MCM-41 supported Ru catalyst prepared by a formaldehyde reduction process

Ru/MCM-41 catalyst prepared by an impregnation–formaldehyde reduction method showed higher catalytic activity and sorbitol selectivity than other catalysts in the hydrogenation of glucose. SEM and XRD indicated the partial surface properties of Ru/MCM-41. Moreover, Ru dispersion and Ru surface area of Ru/MCM-41 were determined by pulse chemisorption, and the result further proved that Ru/MCM-41 had higher catalytic activity. A catalyst recycling experiment demonstrated that Ru/MCM-41 was a better catalyst and it could be reused three or four times. A speculated mechanism was proposed to illustrate the detailed process of d-glucose hydrogenation to produce sorbitol.     

Combined action of an enzyme and a metal catalyst on the conversion of d-glucose/d-fructose mixtures into d-mannitol

A process involving both a bio- and a chemo-catalyst has been applied for the conversion of d-glucose/d-fructose mixtures into d-mannitol. Good yields (62–66%) were obtained by using d-glucose isomerase immobilised on silica in combination with a copper-on-silica catalyst (water, pH ∼7, 70°, 50 kg/cm² of hydrogen, trace amounts of buffer, Mg(II), borate, and EDTA). Non-enzymic isomerisation and degradation reactions are negligible under these reaction conditions.     

Efficient biological process characterization by definitive-screening designs: the formaldehyde treatment of a therapeutic protein as a case study

As part of the process-characterization campaign of a candidate vaccine product, a recently developed class of three-level designs—definitive-screening designs—was employed to select a quadratic model that describes the effect of six input process parameters, including protein concentration, formaldehyde-to-protein ratio, lysine concentration, reaction duration, pH, and reaction temperature, on a formylation protein-crosslinking reaction. This design requires only 17 experimental runs. The resulting model was then used to simulate 10,000 runs that account for the variability in the inputs expected on manufacturing scale. The extent of protein polymerization was predicted to be within specifications for all simulated runs, demonstrating the robustness of the unit operation for subsequent process validation and future commercial manufacturing.     

Efficient conversion of wheat straw wastes into biohydrogen gas by cow dung compost

Efficient conversion of wheat straw wastes into biohydrogen gas by cow dung compost was reported for the first time. Batch tests were carried out to analyze influences of several environmental factors on biohydrogen production from wheat straw wastes. The performance of biohydrogen production using the raw wheat straw and HCl pretreated wheat straw was then compared in batch fermentation tests. The maximum cumulative hydrogen yield of 68.1 ml H2/g TVS was observed at 126.5 h, the value is about 136-fold as compared with that of raw wheat straw wastes. The maximum hydrogen production rate of 10.14 ml H2/g TVS h was obtained by a modified Gompertz equation. The hydrogen content in the biogas was 52.0% and there was no significant methane observed in this study. In addition, biodegradation characteristics of the substrate were also discussed. The experimental results showed that the pretreatment of the substrate plays a key role in the conversion of the wheat straw wastes into biohydrogen by the composts generating hydrogen.     

Theoretical mechanistic study of the formic acid decomposition assisted by a Ru(II)-phosphine catalyst

There is considerable evidence, which we discuss, indicating that compressibility and available free space in the crystal lattice are among the factors that govern the sensitivity of an explosive compound. Expanding and extending earlier work, we demonstrate, for 25 explosives, that there is an overall general tendency for greater impact sensitivity as the estimated free space per molecule increases. More specific relationships can be discerned by looking at subgroups of the compounds. The nitramine sensitivities, most of which are quite high, increase nearly linearly but only very gradually with free space. The nitroaromatics cover a wide range of sensitivities but all have an approximately similar intermediate level of free space. The remaining types of compounds show a reasonable sensitivity–free space relationship with one outlier: FOX-7 (1,1-diamino-2,2-dinitroethylene).     

Seeded conversion of recombinant prion protein to a disulfide-bonded oligomer by a reduction-oxidation process

The infectious form of prion protein, PrP(Sc), self-propagates by its conversion of the normal, cellular prion protein molecule PrP(C) to another PrP(Sc) molecule. It has not yet been demonstrated that recombinant prion protein can convert prion protein molecules from PrP(C) to PrP(Sc). Here we show that recombinant hamster prion protein is converted to a second form, PrP(RDX), by a redox process in vitro and that this PrP(RDX) form seeds the conversion of other PrP(C) molecules to the PrP(RDX) form. The converted form shows properties of oligomerization and seeded conversion that are characteristic of PrP(Sc). We also find that the oligomerization can be reversed in vitro. X-ray fiber diffraction suggests an amyloid-like structure for the oligomerized prion protein. A domain-swapping model involving intermolecular disulfide bonds can account for the stability and coexistence of two molecular forms of prion protein and the capacity of the second form for self-propagation.     

The sodium cycle in methanogenesis. CO2 reduction to the formaldehyde level in methanogenic bacteria is driven by a primary electrochemical potential of Na+ generated by formaldehyde reduction to CH4

CH4 formation from CO2 and H2 rather than from formaldehyde and H2 in methanogenic bacteria is inhibited by uncouplers, indicating that CO2 reduction to the formaldehyde level is energy-driven. We report here that in Methanosarcina barkeri the driving force is a primary electrochemical sodium potential (delta mu Na+) generated by formaldehyde reduction to CH4. This is concluded from the following findings. 1. CO2 reduction to CH4 was insensitive towards protonophores, when the Na+/H+ antiporter was inhibited; under these conditions delta mu Na+ was 120 mV (inside negative), whereas both delta mu H+ and the cellular ATP content were low. 2. CO2 reduction to CH4, rather than formaldehyde reduction, was sensitive towards Na+ ionophores, which dissipated delta mu Na+. 3. CO2 reduction to CH4, in the presence of protonophores and Na+/H+ antiport inhibitors, was coupled with the extrusion of 1-2 mol Na+/mol CH4, and formaldehyde reduction to CH4 was coupled with the extrusion of 3-4 mol Na+/mol CH4. Thus during CO2 reduction to the formaldehyde level 2-3 mol Na+ were consumed.     

The conversion of cellulose into carboxylic acids by a drastic oxygen-alkali treatment

Cotton cellulose was treated with 1 and 3 m sodium hydroxide at 170–190°C under oxygen pressure of 200 and 400 kPa. About 60–70% of the cellulose was converted into low molecular weight carboxylic acids, which were analysed by capillary gas-liquid chromatography-mass spectrometry. In all 60 acids were identified, of which formic, glycolic, lactic, oxalic, 2,3,4-trideoxyhexaric and 3,4-dideoxyhexaric acids were the main compounds. Several C₇−C₁₀ hydroxy dicarboxylic acids were also detected, but these remained mainly unidentified.     

The efficiency of conversion of metabolisable protein into milk true protein over a range of metabolisable protein intakes

The aim of this work was to test the robustness of the 0.68 estimate of the efficiency of conversion of metabolisable protein into true milk protein (Agriculture and Food Research Council (AFRC), 1993) for protein-limiting diets and to determine whether a different value is appropriate for practical rationing. Seventy-two multiparous cows were blocked on the basis of milk energy output per unit of dry matter intake (DMI), and allocated at random to one of four treatments. Treatments supplied metabolisable energy (ME) at a fixed level to individuals within a block, but varied metabolisable protein (MP) supply from 25% below the estimated requirements, through -12.5% and +12.5% up to 25% above requirements for the average performance of animals within blocks at the start of the study. Cows were offered diets to meet their predicted ME requirements for each 3-week period with measurements performed in the last week of each period. Milk protein output was regressed against the estimated MP available for production for each cow and the efficiency of conversion of MP into milk true protein was calculated, assuming a maintenance requirement according to the MP system. The efficiency of conversion of MP into milk true protein decreased with the increasing supply of MP from 0.77 to 0.50. Using an iterative approach to determine the best fit of the data when supply matched requirement resulted in a range of efficiency values between 0.62 and 0.64 g of true milk protein per g of MP.     

Self-assembly of synthetic zinc chlorins in a silicate micelle prepared by sol-gel process

Zinc methyl 3-devinyl-3-hydroxymethyl-pyropheophorbide-a (1), a good model compound of light-harvesting pigments of green photosynthetic bacteria, formed self-aggregates in the presence of octadecyltriethoxysilane and tetraethoxysilane in an aqueous solution to exhibit visible absorption spectra similar to the natural antenna. Base-catalyzed cross-linked polymerization of the additive Si-ORs (R=ethyl and H) afforded the formation of a siloxane network (Si-O-Si) on the surface of the self-assemblies of 1. The resulting microcapsules were stable to tolerate the deaggregation to monomeric 1 by addition of surfactant Triton X-100 more largely than the corresponding micelles before polymerization.     

Evidence for conversion of N-Tyr-MIF-1 into MIF-1 by a specific brain aminopeptidase

N-Tyr-MIF-1 (Tyr-Pro-Leu-Gly·NH₂), an immunoreactive neuropeptide exhibiting saturable high affinity binding in rat brain was found to be converted into MIF-1 (Pro-Leu-Gly·NH₂) by a specific brain aminopeptidase present in rat brain homogenates or cytosol, but with low activity associated with synaptosomal plasma membranes and microsomes. Conversion occurred at a rate of 16 μmol per g w/wt per h and was unaffected by puromycin but inhibited by bestatin (I₅₀, 5 × 10^?5 M). Aminopeptidases purified from cytosolic fractions of rat brain (arylamidase), mouse brain (Mn²⁺-activated aminopeptidase) or porcine kidney (leucine aminopeptidase) were inactive towards N-Tyr-MIF-1 but degraded MIF-1 with release of Leu-Gly·NH₂ as detected by RP-HPLC procedures. Morphiceptin (Tyr-Pro-Phe-Pro·NH₂), a μ opioid agonist, also acted as a substrate for the N-Tyr-MIF-1 converting enzyme with cleavage of the Tyr-Pro bond. These tetrapeptides, but not MIF-1 or its N-blocked analogs, were degraded in vitro by a metalloendopeptidase purified from kidney membranes. Since dipeptide products were not detected for crude extracts, a significant role for brain metalloendopeptidase on turnover can be excluded. Thus the results point to the presence of a specific (X-Pro-degrading) aminopeptidase in brain cytosol as an enzyme responsible for converting N-Tyr-MIF-1 and inactivating morphiceptin.     

Direct one-pot conversion of acylated carbohydrates into their alkylated derivatives under heterogeneous reaction conditions using solid NaOH and a phase transfer catalyst

A convenient one-pot protocol for the direct conversion of acyl-protected carbohydrates into their alkylated counterparts has been developed by using alkyl halides in the presence of solid sodium hydroxide and a phase transfer catalyst. These economically convenient, mild, two-phase reaction conditions allow the preparation of a variety of monosaccharide intermediates for use in the synthesis of complex oligosaccharides.     

Efficient photoinactivation of methicillin-resistant Staphylococcus aureus by a novel porphyrin incorporated into a poly-cationic liposome

Antimicrobial photodynamic therapy is emerging as a promising therapeutic modality for bacterial infections. Our studies aim at identifying strategies for optimizing the antibacterial activity of porphyrin-type photosensitisers. The photoinactivation properties of a novel, positively charged meso-substituted porphyrin, namely 5-[4-(1-dodecanoylpyridinium)]-10,15,20-triphenyl-porphyrin were tested against a typically antibiotic-resistant pathogen, such as methicillin-resistant Staphylococcus aureus. This porphyrin is characterized by an unusually large quantum yield (0.95) for the generation of the hyper-reactive oxygen species, singlet oxygen. In spite of this, it exhibits a relatively low photosensitising activity against bacteria when dissolved in a homogeneous aqueous solution or incorporated into neutral lipid vesicles. On the contrary, a dramatic potentiation of the photocydal effect takes place when polycationic agents such as liposomes of N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride are used as carriers. The cationic carrier primarily acts as a disorganizing agent for the native three-dimensional architecture of the bacterial wall, thereby enhancing its permeability to the photosensitiser. Consequently, the drug can deeply penetrate into the plasma membrane, and rapidly impair selected enzymic activities leading to cell death. Thus, the combination of positively charged drugs and cationic delivery systems appears to represent an innovative modality for achieving an efficient antimicrobial activity and opens new avenues for the development of this phototherapeutic application.     

Genetically engineered Pichia pastoris yeast for conversion of glucose to xylitol by a single-fermentation process

Xylitol is industrially synthesized by chemical reduction of d-xylose, which is more expensive than glucose. Thus, there is a growing interest in the production of xylitol from a readily available and much cheaper substrate, such as glucose. The commonly used yeast Pichia pastoris strain GS115 was shown to produce d-arabitol from glucose, and the derivative strain GS225 was obtained to produce twice amount of d-arabitol than GS115 by adaptive evolution during repetitive growth in hyperosmotic medium. We cloned the d-xylulose-forming d-arabitol dehydrogenase (DalD) gene from Klebsiella pneumoniae and the xylitol dehydrogenase (XDH) gene from Gluconobacter oxydans. Recombinant P. pastoris GS225 strains with the DalD gene only or with both DalD and XDH genes could produce xylitol from glucose in a single-fermentation process. Three-liter jar fermentation results showed that recombinant P. pastoris cells with both DalD and XDH converted glucose to xylitol with the highest yield of 0.078 g xylitol/g glucose and productivity of 0.29 g xylitol/L h. This was the first report to convert xylitol from glucose by the pathway of glucose–d-arabitol–d-xylulose–xylitol in a single process. The recombinant yeast could be used as a yeast cell factory and has the potential to produce xylitol from glucose.     

Efficient catalytic turnover of cytochrome P450(cam) is supported by a T252N mutation

A Thr (or Ser) residue on the I-helix is a highly conserved structural feature of cytochrome P450 enzymes. It is believed to be indispensable as a proton delivery shuttle in the oxygen activation process. Previous work showed that P450_cin (CYP176A1), which contains an Asn instead of the conserved Thr, is fully functional in the catalytic oxidation of cineole [D.B. Hawkes, G.W. Adams, A.L. Burlingame, P.R. Ortiz de Montellano, J.J. De Voss, J. Biol. Chem. 277 (2002) 27725-27732]. To determine whether the substitution of Asn for Thr is specific or general, the conserved Thr252 in P450_cam (CYP101) was mutated to generate the T252N, T252N/V253T, and T252A mutants. Steady-state kinetic analysis of the oxidation of camphor by these mutants indicated that the T252N and T252N/V253T mutants have comparable turnover numbers but higher K_m values relative to the wild-type enzyme. Spectroscopic binding assays indicate that the higher K_m values reflect a decrease in the camphor binding affinity. Non-productive H₂O₂ generation was negligible with the T252N and T252N/V253T mutants, but, as previously observed, was dominant in the T252A mutant. Our results, and a structure model based on the crystal structures of the ferrous dioxygen complexes of P450_cam and its T252A mutant, suggest that Asn252 can stabilize the ferric hydroperoxy intermediate, preventing premature release of H₂O₂ and enabling addition of the second proton to the distal oxygen to generate the catalytic ferryl species.     

High yield conversion of sucrose into ethanol by a flocculentZymomonas sp isolated from sugarcane juice

Summary A flocculentZymomonas sp strain was isolated from fermenting sugarcane juice taking advantage of the motility and ethanol tolerance. The capacity of the new isolate to convert glucose and sucrose into EtOH was investigated. using 200 g/l sucrose feed the isolate showed a sucrose uptake and EtOH yield over 3 times higher than those of the test organismZ. mobilis ATCC 10988.     

Efficient gene transfer into silkworm larval tissues by a combination of sonoporation and lipofection

Sonoporation (ultrasound treatment) provides a new and attractive nonviral way of in vivo gene transfer. To access the applicability of this method to the silkworm, Bombyx mori, we have compared the efficiencies of gene transfer by means of lipofection (using an appropriate agent, PDD111), sonoporation (ditto, FluoroGene), and lipofection followed by sonoporation. By these methods, a luciferase expression plasmid was found to be markedly transferred into the haemocoel of newly ecdysed fifth instar silkworm larvae, and also into other tissues although with lower rates compared with the haemocoel. In terms of luciferase activity, the efficiencies of transgene by lipofection plus sonoporation were approximately 6 (hemocytes), 20 (silk glands), 8 (mid-gut), 38 (fat body), 10 (Malpighian tubules), 33 (ovaries), and 16 (testes) times as high as those by lipofection or sonoporation alone. These results demonstrated that the present method is useful to introduce the exogenous DNA into insect organs in vivo.