Arundo donax cane as a precursor for activated carbons preparation by phosphoric acid activation

Canes from Arundo donax, a herbaceous rapid-growing plant, were used as precursor for activated carbon preparation by phosphoric acid activation under a self-generated atmosphere. The influence of the carbonization temperature in the range 400-550 degrees C and of the weight ratio phosphoric acid to precursor (R = 1.5-2.5) on the developed porous structure of the resulting carbons was studied for 1 h of carbonization time. Surface properties of the activated carbons were dependent on a combined effect of the conditions employed. Carbons developed either with R = 1.5 over the range 400-500 degrees C, or with R = 2 at 500 degrees C exhibited surface areas of around 1100 m2/g, the latter conditions promoting a larger pore volume and enhanced mesoporous character. For both ratios, temperature above 500 degrees C led to reduction in porosity development. A similar effect was found for the highest ratio (R = 2.5) and 500 degrees C. The influence of carrying out the carbonization either for times shorter than 1 h or under flowing N2 was also examined at selected conditions (R = 2, 500 degrees C). Shorter times induced increase in the surface area (approximately 1300 m2/g), yielding carbons with smaller mean pore radius. Activated carbons obtained under flowing N2 possessed predominant microporous structures and larger ash contents than the samples derived in the self-generated atmosphere.     

Activated carbon from Eucalyptus camaldulensis Dehn bark using phosphoric acid activation

The powdered activated carbon prepared by phosphoric acid activation was significantly affected by the carbonization temperature and the weight ratio between raw material and phosphoric acid. With an activation time of 1h and an impregnation ratio of 1:1, the activated carbons with better adsorption capacity were obtained at 500 degrees C. A reduction in the adsorption capacity of the carbon product at higher acid content than this was observed, possibly due to the collapse of the micropore structure. The properties of the resulting activated carbon were: bulk density 0.251gcm(-3), ash content 4.88%, yield 26.2%, iodine adsorption 1043mgg(-1), methylene blue adsorption number 427mgg(-1), and BET surface area 1239m(2)g(-1).     

Preparation and characterization of activated carbon from palm shell by chemical activation with K2CO3

Palm shell was used to prepare activated carbon using potassium carbonate (K2CO3) as activating agent. The influence of carbonization temperatures (600-1000 degrees C) and impregnation ratios (0.5-2.0) of the prepared activated carbon on the pore development and yield were investigated. Results showed that in all cases, increasing the carbonization temperature and impregnation ratio, the yield decreased, while the adsorption of CO2 increased, progressively. Specific surface area of activated carbon was maximum about 1170 m2/g at 800 degrees C with activation duration of 2 h and at an impregnation ratio of 1.0.     

High surface area activated carbon prepared from cassava peel by chemical activation

Cassava is one of the most important commodities in Indonesia, an agricultural country. Cassava is one of the primary foods in our country and usually used for traditional food, cake, etc. Cassava peel is an agricultural waste from the food and starch processing industries. In this study, this solid waste was used as the precursor for activated carbon preparation. The preparation process consisted of potassium hydroxide impregnation at different impregnation ratio followed by carbonization at 450-750 degrees C for 1-3 h. The results revealed that activation time gives no significant effect on the pore structure of activated carbon produced, however, the pore characteristic of carbon changes significantly with impregnation ratio and carbonization temperature. The maximum surface area and pore volume were obtained at impregnation ratio 5:2 and carbonization temperature 750 degrees C.     

Reversible immobilization of invertase on Sepabeads coated with polyethyleneimine: optimization of the biocatalyst's stability

Invertase from S. cerevisiae has been immobilized by ionic adsorption on Sepabeads fully coated with PEI. The enzyme was strongly adsorbed on the support (no desorption of the invertase was found under conditions in which all of the enzyme was released from conventional anionic exchanger supports (e.g., DEAE-agarose)). Nevertheless, the enzyme could still be desorbed after its inactivation, and new fresh enzyme could be adsorbed on the supports without detrimental effects on enzyme loading. This is a multimeric enzyme, its minimal oligomerization active state being the dimer, but under certain conditions of pH and concentration it may give larger multimers. Very interestingly, results suggested that the adsorption of the enzyme on this large and flexible polymeric bed was able to freeze some of the different oligomeric structures of the enzyme. Thus, we have found that the enzyme immobilized at certain pH values (pH 8.5) and high enzyme concentration, in which the main enzyme structure is the tetramer, was more stable than immobilized preparations produced in conditions under which oligomerization was not favorable (dimers at low enzyme concentration) or it was too high (e.g., hexamers-octamers at low pH value). The optimal enzyme preparation remained fully active after a 15-day incubation at 50 degrees C and pH 4.5 (conditions of standard industrial use) and presented an optimal temperature approximately 5 degrees C higher than that of soluble enzyme.     

Physicochemical properties of carbons prepared from pecan shell by phosphoric acid activation

Activated carbons were prepared from pecan shell by phosphoric acid activation. The pore structure and acidic surface groups of these carbons were characterized by nitrogen adsorption, Boehm titration and transmittance Fourier infrared spectroscopy (FTIR) techniques. The characterization results demonstrated that the development of pore structure was apparent at temperatures 250 degrees C, and reached 1130m(2)/g and 0.34cm(3)/g, respectively, at 500 degrees C. Impregnation ratio and soaking time at activation temperature also affected the pore development and pore size distribution of final carbon products. At an impregnation ratio of 1.5, activated carbon with BET surface area and micropore volume as high as 861m(2)/g and 0.289cm(3)/g was obtained at 400 degrees C. Microporous activated carbons were obtained in this study. Low impregnation ratio (less than 1.5) and activation temperature (less than 300 degrees C) are favorable to the formation of acidic surface functional groups, which consist of temperature-sensitive (unstable at high temperature) and temperature-insensitive (stable at high temperature) two parts. The disappearance of temperature-sensitive groups was significant at temperature 300 degrees C; while the temperature-insensitive groups are stable even at 500 degrees C. FTIR results showed that the temperature-insensitive part was mostly phosphorus-containing groups as well as some carbonyl-containing groups, while carbonyl-containing groups were the main contributor of temperature-sensitive part.     

Development of mesoporosity during phosphoric acid activation of wood in steam atmosphere

Oak and birch were used as precursors to produce the activated carbons (ACs) with well-developed mesoporosity by phosphoric acid-promoted activation in a steam atmosphere. The effect of experimental variables such as the amount of activating agent, the soaking time and the type of wood on the development of porous structure upon heating at 480 degrees C was investigated. The materials were characterized by N2 adsorption at 77K, mercury porosimetry and elemental analysis. It was demonstrated that increasing impregnation ratio favors the development of micropores and small mesopores of 2-5nm, whereas the soaking time promotes the creation of large mesopores, between 10 and 50nm. Compared to birch, the oak activation using phosphoric acid in the same conditions gives ACs with lower mesopore volume and higher contribution of small mesopores that reflects the differences between both precursors in their biopolymer composition. The presence of steam in the H3PO4 activation process compared to nitrogen facilitates the development of mesoporosity to much higher extent for the birch than that of oak. The ACs prepared in this work show the BET surface area ranging from 800 to 2250m2g(-1), the total pore volume of 0.35-2.04cm3g(-1) with mesopore fraction between 0.06 and 0.68.     

Production of activated carbon from coconut shell: optimization using response surface methodology

The production of activated carbon from coconut shell treated with phosphoric acid (H3PO4) was optimized using the response surface methodology (RSM). Fifteen combinations of the three variables namely; impregnation ratio (1, 1.5, and 2); activation time (10, 20, and 30 min); and activation temperature (400, 450, and 500 degrees C) were optimized based on the responses evaluated (yield, bulk density, average pore diameter, small pore diameter, and number of pores in a unit area). Pore diameters were directly measured from scanning electron microscope (SEM) images. Individual second-order response surface models were developed and contour plots were generated for the optimization analysis. The optimum range identified for impregnation ratio was from 1.345 to 2, while for the activation time was from 14.9 to 23.9 min. For the activation temperature it was from 394 to 416 degrees C. The optimum points are 1.725, 19.5 min, and 416 degrees C, respectively. The models were able to predict well the values of the responses when the optimum variable parameters were validated as proven by the generally acceptable values of the residual percentages. Direct characterization of the pores using the SEM was found to be a good technique to actually see the pores and get actual measurements. Additionally, RSM has also proven to be a good tool in optimization analysis to get not only optimum production condition points but ranges, which are crucial for the flexibility of the production process, as well.     

Fractionation of Eucalyptus grandis chips by dilute acid-catalysed steam explosion

Steam explosion of Eucalyptus grandis has been carried out under various pretreatment conditions (200-210 degrees C, 2-5 min) after impregnation of the wood chips with 0.087 and 0.175% (w/w) H2SO4. This study, arranged as a 2(3) factorial design, indicated that pretreatment temperature is the most critical variable affecting the yield of steam-treated fractions. Pretreatment of 0.175% (w/w) H2SO4-impregnated chips at 210 degrees C for 2 min was the best condition for hemicellulose recovery (mostly as xylose) in the water soluble fraction, reaching almost 70% of the corresponding xylose theoretical yield. By contrast, lower pretreatment temperatures of 200 degrees C were enough to yield steam-treated substrates from which a 90% cellulose conversion was obtained in 48 h, using low enzyme loadings of a Celluclast 1.5 1 plus Novozym 188 mixture (Novo Nordisk). Release of water-soluble chromophores was monitored by UV spectroscopy and their concentration increased with pretreatment severity. The yield of alkali-soluble lignin increased at higher levels of acid impregnation and pretreatment temperatures. Thermoanalysis of these lignin fractions indicated a pattern of lignin fragmentation towards greater pretreatment severities but lignin condensation prevailed at the most drastic pretreatment conditions.     

Hemolytic plate assay for quantification of active human complement component C3 using methylamine-treated plasma as complement source

A hemolytic plate assay specific for active human complement component C3 is described. The method is well suited for tracing active C3 during preparative purification or for screening of plasma samples. The assay is based on activation of the alternative pathway of complement by unmodified rabbit erythrocytes. Plasma treated with methylamine supplies the essential complement components other than C3. The lytic reaction is complete in 5 h at 37 degrees C and is unchanged by incubation overnight. The dose-response curve, i.e., lysis diameter versus logarithm of C3 concentration, is linear within 0.1-10 times normal plasma concentrations of C3. The standard deviation is below 10%. The hemolytic agarose plates are easy and inexpensive to prepare, and they can be stored at 4 degrees C for 2 weeks before use. This paper describes the optimal conditions of the assay and proves its specificity. Its use in C3 preparation and plasma screening for C3 is discussed.     

Activation and injury of Clostridium perfringens spores by alcohols

The activation properties of Clostridium perfringens NCTC 8679 spores were demonstrated by increases in CFU after heating in water or aqueous alcohols. The temperature range for maximum activation, which was 70 to 80 degrees C in water, was lowered by the addition of alcohols. The response at a given temperature was dependent on the time of exposure and the alcohol concentration. The monohydric alcohols and some, but not all, of the polyhydric alcohols could activate spores at 37 degrees C. The concentration of a monohydric alcohol that produced optimal spore activation was inversely related to its lipophilic character. Spore injury, which was manifested as a dependence on lysozyme for germination and colony formation, occurred under some conditions of alcohol treatment that exceeded those for optimal spore activation. Treatment with aqueous solutions of monohydric alcohols effectively activated C. perfringens spores and suggests a hydrophobic site for spore activation.     

Complement-induced histamine release from human basophils. II. Mechanism of the histamine release reaction.

The activation of human serum complement by incubation with zymosan generates C5a which releases histamine from autologous basophils. The characteristics of the C5a-induced histamine release were investigated. It is similar to IgE-mediated reactions in requiring Ca++ and in being inhibited by EDTA. However, it has marked differences from IgE-mediated reactions. C5a, at all concentrations, released histamine completely in less than 2 min. The C5a reaction has a narrow pH optimum that antigen-induced release and occurs well at 17 degrees to 37 degreesC but not at 0 degreesC. The optimal reaction temperature is 25 degrees to 30 degrees C. Unlike the antigen-induced release, no two-stage activation with C5a for the release of histamine could be demonstrated. There was additive release between C5a- IgE-mediated reactions. Leukocytes could be desensitized to the C5a-mediated reaction by 1) incubating the cells at 37 degrees C for 45 min, 2) pretreating the leukocytes with activated serum in the presence of EDTA, and 3) adding the activated serum to the leukocytes at 0 degrees C before transferring to the optimal reaction temperatures. Cells desensitized to the complement-induced release have normal reactions to IgE-mediated histamine release. In parallel experiments, cells from allergic donors desensitized for IgE-mediated reactions by incubation with antigen under sub-optimal conditions release histamine normally upon the addition of C5a. The results indicate that histamine release by C5a involves a mechanism of basophil activation that is different from the pathway involved in the IgE-induced reaction.     

Activation and injury of Clostridium perfringens spores by alcohols.

The activation properties of Clostridium perfringens NCTC 8679 spores were demonstrated by increases in CFU after heating in water or aqueous alcohols. The temperature range for maximum activation, which was 70 to 80 degrees C in water, was lowered by the addition of alcohols. The response at a given temperature was dependent on the time of exposure and the alcohol concentration. The monohydric alcohols and some, but not all, of the polyhydric alcohols could activate spores at 37 degrees C. The concentration of a monohydric alcohol that produced optimal spore activation was inversely related to its lipophilic character. Spore injury, which was manifested as a dependence on lysozyme for germination and colony formation, occurred under some conditions of alcohol treatment that exceeded those for optimal spore activation. Treatment with aqueous solutions of monohydric alcohols effectively activated C. perfringens spores and suggests a hydrophobic site for spore activation.     

Hydrolysis of sorghum straw using phosphoric acid: evaluation of furfural production

Sorghum straw is a waste that has been studied scarcely. The main application is its use as raw material for xylose production. Xylose is a hemicellulosic sugar mainly used for its bioconversion toward xylitol. An alternative use could be its conversion toward furfural. The objective of this work was to study the furfural production by hydrolysis of sorghum straw with phosphoric acid at 134 degrees C. Several concentrations of H(3)PO(4) in the range 2-6% and reaction time (range 0-300 min) were evaluated. Kinetic parameters of mathematical models for predicting the concentration of xylose, glucose, arabinose, acetic acid and furfural in the hydrolysates were found. Optimal conditions for furfural production by acid hydrolysis were 6% H(3)PO(4) at 134 degrees C for 300 min, which yielded a solution with 13.7 g furfural/L, 4.0 g xylose/L, 2.9 g glucose/L, 1.1g arabinose/L and 1.2g acetic acid/L. The furfural yield of the process was 0.1336 g furfural/g initial dry matter was obtained. The results confirmed that sorghum straw can be used for furfural production when it is hydrolyzed using phosphoric acid.     

Response Surface Models To Describe the Effects of Temperature, pH, and Ethanol Concentration on Growth Kinetics and Fermentation End Products of a Pectinatus sp

Growth curve data which had been fitted by use of the Gompertz and logistic functions have permitted the development of mathematical models to describe the growth of a Pectinatus sp. by several variables, namely, temperature, pH, and ethanol concentration. The activation energy of this microorganism was lower at 26 to 35(deg)C than at 15 to 22(deg)C. On the basis of the Arrhenius law, growth rate, maximum population density, and cell yield models have been developed by introducing the different activation energy (E(infa)) values. According to the model, optimal conditions were 35(deg)C, pH 6.5, and 0% (vol/vol) ethanol for the growth rate. For cell density and cell yield, optimal conditions were 32(deg)C, pH 6.0, and 1% (vol/vol) ethanol. No growth was observed for ethanol concentrations above 8% and pH values below 4.0. Other equations have also been made to describe the major end products fermented during fermentation by a Pectinatus sp. The synthesis of propionate and acetate is maximal at 28(deg)C at pHs of 5.5 and 6.25, respectively. This model completes the model suggested by Membre and Tholozan (J. Appl. Bacteriol. 77:456-460, 1994), which includes only one variable, i.e., the glucose concentration.     

Effect of osmolality and oxygen tension on the survival of mouse sperm frozen to various temperatures in various concentrations of glycerol and raffinose

Cryopreserved mouse sperm are beginning to be used to meet the demand of a reliable cost-effective method for maintaining the rapidly expanding numbers of lines of mutant mice. However, successful and reproducible cryopreservation has proven to be a difficult problem. Furthermore, the underlying factors responsible for success or failure are mostly obscure. Several contributors to these difficulties have been identified. Our laboratory has found that mouse sperm are extremely susceptible to the mechanical stresses associated with pipetting, mixing, and centrifugation, and others have found that they are severely limited in their tolerance to osmotic volume changes. We have hypothesized two other contributors to the difficulties. One is that the concentrations of glycerol used in published protocols are substantially lower than those found to be optimal for most mammalian cells. The other hypothesis relates to the fact that mouse sperm membranes are especially susceptible to damage from oxygen-derived free radicals. That damage may reduce their ability to survive freezing. If so, survival ought to increase if the concentration of oxygen is kept low throughout the procedure. To achieve low levels, we have incorporated an Escherichia coli membrane fraction, Oxyrase, into all media. A previous report showed a protective effect. That is confirmed here under a broader range of conditions. The conditions studied have been the individual and interactive effects of the concentrations of glycerol, raffinose, and phosphate-buffered saline (PBS) on motility after freezing at 21 degrees C/min to -70 degrees C. Cryoprotection increased with increasing raffinose concentration, provided that the concentration of PBS was appropriately reduced to hold the total osmolality of nonpermeating solutes to within tolerated limits. Surprisingly, the best results were achieved in the total absence of glycerol. The highest motilities to date (68 +/- 8%) after freezing to -70 degrees C have been achieved using media containing Oxyrase, 0 M glycerol, and 18% raffinose in 14x strength modified PBS. We also determined the motility loss after freezing to intermediate temperatures, i.e., -10 and -30 degrees C. The major motility loss occurred by -10 degrees C, especially in the absence of Oxyrase. These results suggest that a major problem in the freezing of mouse sperm is the physical stress resulting from extracellular ice crystal formation. Oxyrase appears to lessen that damage substantially.     

植酸酶产生菌的选育及固态产酶条件研究

植酸酶催化植酸,并将其盐类水解成肌醇和磷酸,因此植酸酶的使用可以提高植酸磷的吸收利用率,降低饲料成本,同时还可保护生态环境.经分离和亚硝基胍诱变选育,得到一株植酸酶高产菌株绿色木霉LH374,并对该菌株固态发酵产植酸酶的条件和扩大生产进行了研究.结果表明,固态发酵的最佳条件:稻草和米糠的比例为8:2,培养基起始pH为6.5,最适温度为30℃,最适培养时间为96 h,含水量为60%,硫酸铵的流加量为2%.绿色木霉LH37在上述最适条件下生产植酸酶平均可达1 580 U·g^-1.     

The thermal decomposition studies of solid iron bamboo (Dendrocalamus strictus) - potential precursor for eco-materials

Block samples of carbonized solid iron bamboo (Dendrocalamus strictus) - unique genus among bamboos, were prepared by means of slow pyrolysis. They are expected to be promising monolithic supports for various composites. The purpose of this study is to describe the thermal decomposition of rectangular shapes cut from solid stems of Dendrocalamus strictus, raw and pre-charred in a wide range of temperatures: 300, 350, 400, 500 and 600 degrees C. The DTG thermograms of carbonized solid iron bamboo (char), determined at temperatures up to 900 degrees C, exhibited minima even for samples previously pyrolysed at temperatures over 400 degrees C, at which decomposition of plant material have to be completed. For pre-charred samples, the temperature of the DTG peaks increased, while the weight loss registered in the temperature range up to 900 degrees C decreased, with increasing temperature of carbonization. It was found that extension of time of holding at final temperature of carbonization decreased a height of the DTG peaks to full reduction of it after heating along the time of 8h. It was suggested that bamboo tar remaining in vessels after carbonization reacts with the bamboo char creating new compounds that decompose in distinctly higher temperatures.     

Production and comparison of high surface area bamboo derived active carbons

High surface area activated carbons have been produced from the natural biomaterial bamboo, using phosphoric acid as the activating agent. The effects of phosphoric acid impregnation ratio, activation temperature, heating rate on the carbon surface area, porosity and mass yield are presented. Three of these bamboo derived active carbons, surface areas 1337, 1628 and 2123m(2)/g were assessed for their ability to adsorb Acid Red 18 dye from aqueous solution; these results were compared with three conventional adsorbents: activated carbon F400, bone char and peat. Isotherm data were analysed using Langmuir, Freundlich, Redlich-Peterson and Langmuir-Freundlich isotherms. Different isotherms provided the best fit correlations to the adsorption experimental data but the Langmuir-Freundlich equation provided the best overall correlation of data. The adsorption capacities of two of the selected bamboo derived carbons were much greater than the capacities of the other three adsorbents.     

Spontaneous activation of the first component of human complement (C1) by an intramolecular autocatalytic mechanism

For biochemical characterization, the first component of human complement (C1) was reconstituted from physiologic concentrations of purified C1q, 125I C1r, and 131I C1s. Upon incubation at 37 degrees C, C1 spontaneously activated, as evidenced by the characteristic proteolysis of the C1r and C1s polypeptide chains as detected by SDS-PAGE analysis. This spontaneous C1 activation followed first-order kinetics (t 1/2 = 4 min and k = 0.173 min-1) with an activation energy of 19.1 kcal/mol. Spontaneous C1 activation was unaffected by the general protease inhibitor phenylmethylsulfonylfluoride (PMSF) but reversibly blocked by a known inhibitor of C1 activation, nitrophenylguanidinobenzoate (NPGB). Spontaneous C1 activation was measured at C1 concentrations ranging from 9 to 160 nM (i.e., 0.05 to 1.0 times physiologic concentrations). The data indicate that C1 spontaneously activates by an intramolecular autocatalytic mechanism, for first-order kinetics were observed over the entire concentration range with t 1/2 = 4 min at each concentration. However, the percentage of activable C1 decreased with dilution due to C1 dissociation (i.e., C1qr2s2 leads to C1q + C1r2s2). The observed concentration of C1 that spontaneously activated at each dilution equalled the concentration of C1 present as macromolecular C1. When reconstituted C1 was mixed with normal human serum (NHS) and then incubated at 37 degrees C, spontaneous C1 activation was completely inhibited. Pretreating NHS at 56 degrees C for 30 min destroyed its inhibitory activity. In conclusion, C1 spontaneously autoactivates at 37 degrees C by an intramolecular mechanism. This activation is suppressed in NHS.