Selective dehydration of bio-ethanol to ethylene catalyzed by lanthanum-phosphorous-modified HZSM-5: influence of the fusel

Bio-ethanol dehydration to ethylene is an attractive alternative to oil-based ethylene. The influence of fusel, main byproducts in the fermentation process of bio-ethanol production, on the bio-ethanol dehydration should not be ignored. We studied the catalytic dehydration of bio-ethanol to ethylene over parent and modified HZSM-5 at 250°C, with weight hourly space velocity (WHSV) equal to 2.0/h. The influences of a series of fusel, such as isopropanol, isobutanol and isopentanol, on the ethanol dehydration over the catalysts were investigated. The 0.5%La-2%PHZSM-5 catalyst exhibited higher ethanol conversion (100%), ethylene selectivity (99%), and especially enhanced stability (more than 70 h) than the parent and other modified HZSM-5. We demonstrated that the introduction of lanthanum and phosphorous to HZSM-5 could weaken the negative influence of fusel on the formation of ethylene. The physicochemical properties of the catalysts were characterized by ammonia temperature-programmed desorption (NH(3)-TPD), nitrogen adsorption and thermogravimetry (TG)/differential thermogravimetry (DTG)/differential thermal analysis (DTA) (TG/DTG/DTA) techniques. The results indicated that the introduction of lanthanum and phosphorous to HZSM-5 could inhibit the formation of coking during the ethanol dehydration to ethylene in the presence of fusel. The development of an efficient catalyst is one of the key technologies for the industrialization of bio-ethylene.     

Evaluation of the biological stability of waste during landfill stabilization by thermogravimetric analysis and Fourier transform infrared spectroscopy

This study seeks to assess the biological stability of landfilled municipal solid waste (MSW) based on the changes in organic matter, as revealed by thermogravimetric analysis and Fourier transform infrared (FTIR) spectroscopy. Derivate thermogravimetry profiles (DTG) showed a reduction in peak intensity at 200-350 °C (DTG2), while an increase in peak intensity and a shift towards higher temperature at 400-600 °C (DTG3). The decrease in the peak intensity of the aliphatic methylene at 2920 and 2850 cm(-1), and the increase of aromatic substances and polysaccharide at 1640 cm(-1) in the FTIR spectra also confirm the changes. Well-fitted correlations of the peak intensity ratio (2920/1640) and peak area ratio (DTG2/DTG3) to C/N ratio were also established, confirming that the 2920/1640 and the DTG2/DTG3 ratios can be considered as reliable parameters for tracking the biological stability of MSW during landfill stabilization.     

Inactivation of Escherichia coli O157:H7 on radish seeds by sequential treatments with chlorine dioxide, drying, and dry heat without loss of seed viability

We developed and validated a treatment to inactivate Escherichia coli O157:H7 on radish seeds without decreasing seed viability. Treatments with aqueous ClO(2) followed by drying and dry-heat treatments were evaluated for efficacy to inactivate the pathogen. Conditions to dry radish seeds after treatment with water (control) or ClO(2) were established. When treated seeds with high water activity (a(w)) (>0.99) were stored at 45°C and 23% relative humidity (RH), the a(w) decreased to <0.30 within 24 h. Drying high-a(w) seeds before exposing them to dry-heat treatment (≥60°C) was essential to preserve seed viability. The germination rate of radish seeds which had been immersed in water for 5 min, dried at 45°C and 23% RH for 24 h, and heated at 70°C for 48 h or at 80°C for 24 h was not significantly decreased (P ≤ 0.05) compared to that of untreated radish seeds. Sequential treatments with ClO(2) (500 μg/ml, 5 min), drying (45°C, 23% RH, 24 h), and dry heating (70°C, 23% RH, 48 h) eliminated E. coli O157:H7 (5.9 log CFU/g) on radish seeds and, consequently, sprouts produced from them without decreasing the germination rate. These sequential treatments are recommended for application to radish seeds intended for sprout production.     

Biosorption of lead by cotton shells powder: Characterization and equilibrium modeling study

Lead (Pb) is a toxic heavy metal causing serious health risks to humans and animals. In the present study, cotton (Gossypium hirsutum L.) shells powder was used as adsorbent for the treatment of synthetic Pb-contaminated water. The batch scale biosorption capacity of cotton shells powder was evaluated to study the effects of Pb concentrations, adsorbent doses and contact time at constant pH (6) and temperature (25?°C). Results revealed that sorption of Pb increased (q?=?0.09–9.60?mg/g) with increasing Pb concentration (1–15?mg/L) and contact time (15–90?min) while decreasing adsorbent dose (1–0.1?g/100?mL). The maximum Pb removal (90%) was achieved at Pb concentration (1?mg/L), contact time (90?min) and adsorbent dose (1?g/100?mL). Freundlich isotherm model proved best fit for Pb sorption (R²?=?0.99). The cotton shells powder has microporous structure confirmed by SEM, and has BET surface area (45 m²/g) and pore size (2.3 µm). These surface moieties along with various functional groups (C-H, C-O, C=O, O-H, S=O) confirmed by FTIR analysis might involve in Pb removal by complexation and ion exchange mechanisms. The cotton shells powder biomass could be considered as promising adsorbent for the removal of Pb from contaminated water.     

Application of Thermostable Xylanase of Bacillus pumilus in Textile Processing

Desizing of cotton and micropoly fabrics was done using thermostable xylanase from Bacillus pumilus ASH. Micropoly fabric showed better desizing than cotton under same conditions. Violet scale readings from the TEGEWA test after enzymatic desizing for 90 min at pH 7.0 and at 60°C showed the readings falling in the range of 4–5, indicating good desizing efficiency. During bioscouring the weight loss values and liberation of reducing sugars were highest when EDTA was used along with xylanase. The weight loss value of 1.5% was observed for dry cotton fabric after 1 h in case of agitated system at pH 7.0 and at an optimal enzyme dosage of 5 IU/g. The weight loss values and the liberation of reducing sugars were higher in case of cotton fabrics. Wetting time of fabrics was lowered significantly after 60 min of bioscouring using xylanase. Increase in temperature or concentration of surfactant led to further reduction in the wetting time. The whiteness values of fabrics after bioscouring were 0.9% higher than the chemically scoured fabrics indicating good efficacy of xylanase during the scouring process.     

大黄酸和大黄素的热分析及其动力学研究

本文采用热重法(TG)和差热分析法(DTA)测定了大黄酸和大黄素的DTA,TG-DTG曲线。两者的DTA曲线中皆有两个较为明显的吸热峰,第一个在熔化过程中出现,第二个发生在热分解过程中并伴随有明显的失重现象。TG曲线均有一个失重平台,失重率在90%以上。用TG-DTG法对两者在非等温条件下进行热分解动力学研究,把从TG-DTG曲线中取得的数据和31个不同的方程采用Achar微分法和Madhusudanan-Krishnan-Ni-nan(MKN)积分法对其进行非等温分解动力学研究,得到动力学参数活化能(E和指前因子A)和分解动力学机理及方程。得出结论:大黄酸和大黄素的动力学方程为dα/dt=Aexp(-E/RT)3/2(1-α)4/3[1/(1-α)1/3-1]-1和dα/dt=Aexp(-E/RT)3/2(1-α)2/3[1/(1-α)1/3]-1,其分解等合3D抗理。二者的活化能E(kJ/mol)分别为117.6和86.79,lnA/s-1分别是36.72和27.44。     

Quantification of CPT13 in rat plasma using LC-MS/MS for a pharmacokinetic study

A new, simple, sensitive and specific reversed-phase high performance liquid chromatographic (HPLC) method using tandem mass spectrometry detection was initially developed and validated for the analysis of 10-(2-pyrazolyl-ethoxy)-(20S)-camptothecin (CPT13) in rat plasma. Pretreatment of the sample obtained from plasma involved a single protein precipitation step with using acetonitrile containing 0.1% formic acid. An aliquot of 20 μl was injected into a C-18 column. The chromatographic separation was achieved using the mobile phase consisting of acetonitrile:water (35:65) at a flow rate of 1.0 mL/min. The total run time for each sample was 10 min, and camptothecin (CPT, IS) and CPT13 were well separated with retention times of 5.1 min and 5.6 min, respectively. Detection was performed using a triple quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode via an electrospray ionization (ESI) source. The calibration curve was linear (r2 = 0.9998) over the concentration range of 1-1000 ng/mL, with a LLOQ of 1 ng/mL for CPT13. The inter- and intra-day precision (%R.S.D.) were <2.58% and 6.28%, respectively, and the accuracies (%) were within the range of 97.34-110.67%. CPT13 in rat plasma was stable when stored at -20 °C or 4 °C for three freeze-thaw cycles, The method was employed for the first time during pharmacokinetic studies of CPT13 in rats following a single intravenous dose (0.1 mg/kg) and three different oral doses (50 mg/kg, 30 mg/kg, and 10 mg/kg). This fully validated method was successfully applied to a pharmacokinetic study of CPT13 in rats.     

Thermal analysis for differentiating between oleaginous and non-oleaginous microorganisms

The potential of thermal analysis for differentiating between oleaginous and non-oleaginous microorganisms was investigated using thermogravimetry (TG) and differential thermal analysis (DTA). The model oleaginous microorganisms used in the present study were the fungi, Mortierella alpina IFO32281 and Mortierella alliacea YN-15, the unicellular alga, Aurantiochytrium sp. CB 15-5, and the yeast, Rhodosporidium toruloides DMKU3-TK 16. Escherichia coli JM109, Rhodococcus opacus B-4, and Saccharomyces cerevisiae were used as the control non-oleaginous microorganisms. In simultaneous TG and DTA, the furnace temperature was linearly increased from 30 to 280 °C, decreased to 30 °C, linearly increased from 30 to 360 °C, and then isothermally held at 360 °C for 30 min. This two-step linear temperature program was effective in resolving overlapping exothermic peaks in the DTA curves in the temperature range from 280 to 360 °C. Heat evolved from a microbial sample was estimated from the area under the exothermic peak between 280 and 360 °C using indium as a standard material. There was a linear relationship between the exothermic heat and total lipid content of the tested microorganisms. Exothermic heat per dry sample mass (kJ/g) in the temperature range from 280 to 360 °C is a promising measure for differentiating between oleaginous and non-oleaginous microorganisms.     

Preparation of cationic cotton with two-bath pad-bake process and its application in salt-free dyeing

Cationic cotton was prepared by a designed two-bath pad-bake process with 3-chloro-2-hydroxypropyltrimethylammonium chloride as cationizing reagent to realize recycle utilization of the reagent and continuous processing of cationization. Experiments showed that 8.0% (o.w.bath) of the reagent, 1:1 of molar ratio of sodium hydroxide to the reagent, 60 °C and 6 min of baking temperature and time were selected for cationization and the obtained cationic cotton was suitable for application in salt-free reactive dyeing. The structures of both the untreated and cationic fibers were investigated by X-ray diffraction and scanning electronic microscopy. Higher dye utilization and color yields could be realized on the cationic cotton than that on the untreated one in the conventional dyeing. Levelness dyeing and good fastness properties of the dyes on the cationic fabrics were obtained. Besides, colorimetric properties and mechanical strength of the dyed fabrics were both evaluated to show applicability of this preparation process of cationic cotton.     

Synthesis of partly debranched starch-g-poly(2-acryloyloxyethyl trimethyl ammonium chloride) catalyzed by horseradish peroxidase and the effect on adhesion to polyester/cotton yarn

We performed a dual-modification of starch via debranching and graft copolymerization to improve its adhesion to fibers. We synthesized the partly debranched starch-g-poly(2-acryloyloxyethyl trimethyl ammonium chloride) (PDS-g-PATAC) using horseradish peroxidase in the presence of hydrogen peroxide and acetylacetone. PDSs of different molecular structures were prepared by debranching waxy cornstarch for different periods of time. With increasing debranching time, the degree of hydrolysis of PDS increased from 0.85 % (10 min) to 1.13 % (30 min), while the degree of branching decreased from 8.37 % to 7.99 %. Fourier transform infrared analysis confirmed that ATAC units had been successfully grafted onto the starch (debranched or not debranched). The degree of substitution (DS) and grafting ratio (GR) of the PDS-g-PATACs were characterized by ¹H nuclear magnetic resonance. The DS and GR of grafted starches positively related with debranching time. Thermogravimetry-differential thermogravimetry analysis showed that grafted starch had lower thermal stability than ungrafted starch. The adhesion of PDS-g-PATAC to polyester/cotton yarns was evaluated. The PATAC chains grafted onto the starch enhanced the adhesion of starch to polyester/cotton yarn. The grafted starch produced from the copolymerization of PDS (after debranching for 10 min), exhibited the strongest adhesion to polyester/cotton yarn with a resulting tensile strength of 98.20 N.     

石楠和蜡梅茎结冰动力学过程的差热扫描分析

在（0.66 ±0.2）℃/min（0℃~-20℃）的降温速度下,采用高分辨率差热分析法分别对石楠（Photinia serrulata Lindl.）和蜡梅（Chimonanthus praecox（L.）Link）活体幼茎和经过10 min高温煮沸的幼茎在结冰过程中的热力学行为进行分析,并根据茎的形态解剖结构对他们的结冰特征进行研究。结果显示：石楠和蜡梅的活体幼茎在结冰过程中的差热扫描曲线均出现3个放热峰;而经过高温杀死后的茎仅出现1个单放热峰。分析结果表明,2种植物活体幼茎的3个放热峰可能与其木质部、质外体、韧皮部、形成层的结冰、脱水以及髓组织的结冰、脱水过程有关。进一步采用生理盐水浸湿的滤纸进行模拟实验,结果发现差热扫描曲线出现与高温杀死的茎类似的放热峰。实验结果表明,采用高分辨率差热分析法可以探测植物组织结冰过程中的放热强度、结冰温度及其与结冰动力学过程相关的大量细节,适用于植物的结冰动力学分析。     

The effect of temperature and pH on the motility and viability of ostrich sperm

As the chemical environment of semen diluents can have a profound effect on sperm quality, we examined the effect of temperature and pH on the motility and viability of sperm in the ostrich. Semen was collected from four males, each male being replicated three times. Ejaculates were diluted and incubated for 10 min at 20°C and 40°C in four different buffers, temperature adjusted at pH 6, 7, 8 and 9 respectively. Average path velocity (VAP), curvilinear velocity (VCL), straight-line velocity (VSL), linearity (LIN), beat cross frequency (BCF) and amplitude of lateral displacement (ALH) were then recorded for each sample using CASA. The viability of sperm was assessed using nigrosin-eosin staining. Sperm incubated at 40°C had higher motility parameters, except for ALH. At 40°C, VAP, VSL and LIN increased with pH while VCL, BCF and ALH were higher for lower pHs. The viability of sperm was not affected by temperature but decreased at pH values>7. A pH in the neutral range appeared to yield higher quality sperm after in vitro storage at 20°C. However, the effect of different pH levels and temperatures on sperm longevity needs to be investigated further to develop viable ostrich specific diluents.     

New development for combined bioscouring and bleaching of cotton-based fabrics

A thorough investigation into conditions appropriate for effecting combined eco-friendly bioscouring and/or bleaching of cotton-based fabrics was undertaken. Fabrics used include cotton, grey mercerized cotton, cotton/polyester blend 50/50 and cotton/polyester blend 35/65. The four cotton-based fabric were subjected to bioscouring by single use of alkaline pectinase enzymes or by using binary mixtures of alkaline pectinase and cellulase enzymes under a variety of conditions. Results of bioscouring show that, the bioscoured substrates exhibit fabrics performances which are comparable with these of the conventional alkali scouring. It has been also found that, incorporation of ethylenediaminetetraacetic acid (EDTA) in the bioscouring with mixture from alkaline pectinase and cellulase improves the performance of the bioscoured fabrics. Addition of β-cyclodextrin to the bioscouring solution using alkaline pectinase in admixtures with cellulase acts in favor of technical properties and performance of the bioscoured fabrics. Concurrent bioscouring and bleaching by in situ formed peracetic acid using tetraacetylethylenediamine (TAED) and H₂O₂ was also investigated. The results reveal unequivocally that the environmentally sound technology brought about by current development is by far the best. The new development involves a single-stage process for full purification/preparation of cotton textiles. The new development at its optimal comprises treatment of the fabric with an aqueous formulation consisting of alkaline pectinase enzyme (2 g/L), TAED (15 g/L), H₂O₂ (5 g/L), nonionic wetting agent (0.5 g/L) and sodium silicate (2 g/L). The treatment is carried out at 60 °C for 60 min. Beside the advantages of the new development with respect to major technical fabric properties, it is eco-friendly and reproducible. This advocates the new development for mill trials.     

Kinetic studies on the adsorption of Cd2+, Cu2+ and Zn2+ ions from aqueous solutions by cassava (Manihot sculenta Cranz) tuber bark waste

The kinetics of Cd2+, Cu2+ and Zn2+ adsorption onto pure and thioglycolic acid treated cassava tuber bark wastes (CTBW) were investigated using a batch sorption technique at 30 degrees C. Kinetic data suggested that the adsorption process was exothermic, the rate limiting sorption step was physisorption and adsorption rates could be best described by a pseudo-second order model. Rate coefficients were determined to range between 1.39x10(-2)min(-1) and 5.94x10(-2)min(-1), 1.46x10(-3)min(-1) and 5.76x10(-3)min(-1) and 0.69x10(-3)min(-1) and 5.8x10(-3)min(-1) for Cd2+, Cu2+ and Zn2+, respectively. The results from these studies indicated that the sorption process is fast and stable. The adsorption equilibria were evaluated using the Langmuir equation and the monolayer sorption capacity was found to range between 5.88-26.3mg/g, 33.3-90.9 mg/g and 22.2-83.3mg/g for Cd2+, Cu2+ and Zn2+, respectively. Negative values of DeltaG(ads)(0) indicated that the adsorption process was spontaneous and exothermic in nature.     

Moist-heat resistance, spore aging, and superdormancy in Clostridium difficile

Clostridium difficile spores can survive extended heating at 71°C (160°F), a minimum temperature commonly recommended for adequate cooking of meats. To determine the extent to which higher temperatures would be more effective at killing C. difficile, we quantified (D values) the effect of moist heat at 85°C (145°F, for 0 to 30 min) on C. difficile spores and compared it to the effects at 71 and 63°C. Fresh (1-week-old) and aged (≥20-week-old) C. difficile spores from food and food animals were tested in multiple experiments. Heating at 85°C markedly reduced spore recovery in all experiments (5 to 6 log(10) within 15 min of heating; P < 0.001), regardless of spore age. In ground beef, the inhibitory effect of 85°C was also reproducible (P < 0.001), but heating at 96°C reduced 6 log(10) within 1 to 2 min. Mechanistically, optical density and enumeration experiments indicated that 85°C inhibits cell division but not germination, but the inhibitory effect was reversible in some spores. Heating at 63°C reduced counts for fresh spores (1 log(10), 30 min; P < 0.04) but increased counts of 20-week-old spores by 30% (15 min; P < 0.02), indicating that sublethal heat treatment reactivates superdormant spores. Superdormancy is an increasingly recognized characteristic in Bacillus spp., and it is likely to occur in C. difficile as spores age. The potential for reactivation of (super)dormant spores with sublethal temperatures may be a food safety concern, but it also has potential diagnostic value. Ensuring that food is heated to >85°C would be a simple and important intervention to reduce the risk of inadvertent ingestion of C. difficile spores.     

Antibacterial cotton fabrics treated with core-shell nanoparticles

Multifinishing treatment of cotton fabrics was carried out using core-shell nanoparticles that consists of silver nanoparticles (Ag(0)) as core and chitosan-O-methoxy polyethylene glycol (CTS-O-MPEG) as shell. The synthesized (Ag(0)-CTS-O-MPEG) core-shell nanoparticle was applied to cotton fabrics using the conventional pad-dry-cure method. The finished fabrics were examined for their morphological features and surface characteristics by making use of scanning electron microscope (SEM-EDX), which reveals the well dispersion of (Ag(0)-CTS-O-MPEG) core-shell nanoparticles on cotton fabrics. Factors affecting the treatment such as core shell nanoparticles, citric acid (CA) concentration as well as curing temperature were studied. The treated fabrics, at optimum condition of 1% core shell nanoparticles, 5% citric acid, drying at 80°C, curing at 160°C for 2 min, showed excellent antibacterial activity against Gram-negative Escherichia coli (E. coli) and Gram-positive bacteria Staphylococcus aureus (S. aureus), even after 20 washing cycles in addition to an enhancement in crease recovery angles (CRA) along with a slight improvement in tensile strength (TS).     

Characterization of primary thermal degradation features of lignocellulosic biomass after removal of inorganic metals by diverse solvents

Poplar wood powders were treated with distilled water, tap water, HCl and HF, respectively, to remove inorganics from the biomass and to investigate effect of demineralization processes on pyrolysis behavior of the biomass. TG and DTG revealed that maximum degradation temperatures rose slightly from 362°C for control to 372°C, 366°C and 368°C after demineralization with distilled water, HCl and HF, respectively. Maximum degradation rates also increased from 0.96%/°C for control to 1.15%/°C for HF-biomass, 1.23%/°C for DI-H(2)O-biomass, and 1.55%/°C for HCl-biomass. Analytical pyrolysis-GC/MS of demineralized biomasses produced approximately 45 pyrolysis compounds. Total amount of low molecular weight compounds, such as acetic acid, acetol, and 3-hydroxypropanal, was significantly lowered in the demineralized biomasses. But levoglucosan increased 2-10-folds in the demineralized biomasses. One of the features regarding lignin derivatives was the reduction of the amount of C6-type phenols, such as phenol, guaiacol, and syringol after demineralization.     

Optimization of production and reaction conditions of polygalacturonase from Byssochlamys fulva

In the present study, the optimization of production and reaction conditions of polygalacturonase produced by a fungus Byssochlamys fulva MTCC 505 was achieved. The production of polygalacturonase with a considerable activity of 1.28 IU/ml was found when the culture was shaken at 30°C for 5 days in 100 ml of medium containing (w/v) 10 g/l pectin, 2 g/l NaNO?, 1 g/l KH?PO?, 0.5 g/l KCl, 0.5 g/l MgSO?. 7H?O, 0.001 g/l FeSO?. 7H?O, 0.001 g/l CaCl?. The best carbon and nitrogen source for this enzyme were pectin (1%) and Ca(NO?)? (0.1%), respectively. The enzyme gave maximum activity at incubation time of 72 h, temperature of 30°C and pH 4.5. During the optimization of reaction conditions, the enzyme showed maximum activity in sodium citrate buffer (50 mM) of pH 5.5 at 50°C reaction temperature for 15 minutes of incubation. The enzyme showed greater affinity for polygalacturonic acid as substrate (0.5%). Km and Vmax values were 0.15 mg/ml and 4.58 μmol/ml/min. The effect of various phenolics, thiols, protein inhibitors and metal ions on the enzyme activity was investigated. The enzyme was quite stable at 4°C and 30°C. At 40°C the half life of the enzyme was 6 h and at 60°C it was 2 h.     

Quantification of damage at different stages of cryopreservation of endangered North American bison (Bison bison) semen and the effects of extender and freeze rate on post-thaw sperm quality

Semen cryopreservation is an important technique for the banking of animal germplasm from endangered species and exploitation of genetically superior sires through artificial insemination. Being a member of bovidae family, bison semen has poor freezing ability as compared to dairy and beef bulls' semen. This study was designed to quantify the damage to bison sperm at different stages of cryopreservation, and to determine the effects of extender (commercial Triladyl(?) vs. custom made tris-citric acid [TCA]) and freeze rate (-10, -25 and -40°C/min) on post-thaw quality of bison semen. Semen was collected from five bison bulls (three woods and two plains) via electroejaculation. In Experiment 1, semen was diluted in Triladyl? extender and frozen with freeze rate -10°C/min. Sperm motility characteristics were recorded in fresh, diluted, cooled (4°C) and freeze-thawed semen using computer-assisted sperm analyzer (CASA). In Experiment 2, semen was diluted in Triladyl? or TCA extender, and frozen with three different freeze rates, i.e. -10, -25 or -40°C/min. Thawing was performed at 37°C for 60s. Post-thaw sperm motility characteristics were assessed using CASA, and sperm structural characteristics (plasma membrane, mitochondrial membrane potential and acrosomes) were evaluated using flow cytometer, at 0 and 3h while incubating semen at 37°C. In Experiment 1, total and progressive motilities did not differ among pre-freeze stages of cryopreservation (P>0.05). However, sperm total and progressive motilities declined (P<0.001) in freeze-thawed semen by 35% and 42%, respectively, compared to after cooling (pre-freeze) semen. In Experiment 2, Triladyl?, as compared to TCA, yielded greater (P<0.05) post-thaw sperm total motility (41% compared to 36%) and progressive motility (34% compared to 29%) at 0h, respectively. The percent change in post-thaw sperm total and progressive motilities, VAP, VCL, VSL, IPM-high ΔΨm and IPM-IACR during 3h incubation at 37°C, was less (P<0.05) in TCA than in Triladyl?. There was an effect of freeze rate on post-thaw sperm average path velocity at 0h, and total motility, progressive motility, VCL, IPM and IPM-IACR at 3h were the greatest (P<0.05) when bison semen was frozen at -40°C/min. Likewise, the percent change in post-thaw sperm total and progressive motilities, during 3h incubation at 37°C, was less (P<0.05) in bison semen frozen at -40°C/min. All post-thaw bison sperm characteristics decreased (P<0.05) from 0h to 3h, during incubation at 37°C. In conclusion, the maximum damage to bison sperm occurred during freeze-thaw processes. Post-thaw total and progressive motilities of bison sperm were greater in Triladyl? at 0h whereas sperm survival was greater in TCA extender during 3h post-thaw incubation. Bison sperm had greater survival (P<0.05) when frozen at -40°C/min freeze rate.     

Highly thermostable xylanase purified from Rhizomucor miehei NRL 3169

A thermostable xylanase was purified and characterized from the thermophilic fungus Rhizomucor miehei (Cooney & Emerson) Schipper. The enzyme was purified to homogeneity by ammonium sulfate precipitation, sephadex G-100 gel filtration and diethylaminoethyl cellulose anion exchange chromatography with a 29.1-fold. The enzyme was highly active within a range of pH from 5.0 to 6.5. The optimum temperature of the purified enzyme was 75°C. The enzyme showed high thermal stability at 70°C and 75°C and the half-life of the xylanase at 90°C was 30 min. Km and Vmax values at 50°C of the purified enzyme were 0.055 mg/ml and 113.5 μmol min?1 mg?1 respectively. The enzyme was activated by Ca2+, Cu2+, K+ and Na+. On the other hand, Ag2+, Hg2+, Ba2+, and Zn2+ inhibited the enzyme. The molecular weight of the xylanase was estimated to be 27 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The present study is among the first works to examine and describe a secreted highly thermostable endoxylanase from the Rhizomucor miehei fungus. This enzyme displays a number of biochemical properties that make it a potentially strong candidate for industrial and commercial application in pulp bleaching.