Effect Of Different Pretreatment Methods Research Articles

The Effect of Different Pretreatment Methods and Operational Conditions on the Biohydrogen Production Potential of Aged Anaerobic Culture

In this study, the preconditioning of anaerobic culture by aging was carried out followed by testing various pretreatments (heat shock and alkali) to improve H2 production. It has turned out that aging could enhance the hydrogen generation meanwhile heat- and alkali curing led to comparable H2 formation activity with a slight advantage of the former one. Subsequently, the heat treated microflora was applied under different pHs and Gas to Liquid phase ratios and according to the statistical analysis both were significant factors since they affected not only the hydrogen productivity but also the developing H2 partial pressures in the system. Furthermore, an indirect relationship between hydrogen productivity and hydrogen partial pressure was found, which means that higher H2 turnouts were associated with lower H2 partial pressure conditions. The PCR-DGGE analysis of the microbial community after heat- and alkali pretreatments showed the dominancy of Clostridium species. Keywords: Biohydrogen, culture aging, pretreatment, experimental design, partial pressure, microbial monitoring.

The effect of different pretreatment methods of PMMA-based crowns on the long-term tensile bond strength to dentin abutments

The objective of the study was to test the effect of different pretreatments on tensile bond strength (TBS) of adhesively bonded CAD/CAM-generated polymethyl methacrylate (PMMA) crowns to dentin. Two hundred human molars were prepared and divided into 20 groups (n = 10/group). PMMA crowns were pretreated thusly: Monobond Plus/Heliobond (MH), Visio.link (VL), Ambarino P60 (AM), VP connect (VP), and nontreated as control groups (CG). Two resin cements were used for cementation of crowns: Clearfil SA Cement (CSA) and Variolink II (VAR). TBS was measured initially (24 h water storage, 37 °C) and after aging (5,000 thermal cycles, 5/55 °C). TBS was analyzed using one-way ANOVA with Scheffé post hoc, unpaired Student t, Mann-Whitney U, Kruskal-Wallis H, and chi-squared tests. Within CSA, pretreatment with MH and VL showed higher initial TBS compared with AM-treated groups. All other groups showed no statistical differences. For MH, VL, AM, and VP in combination with CSA, a negative impact of aging was observed (p < 0.001), whereas in all VAR groups, no impact was measured. Pretreatment with MH (p = 0.001) and VP (p = 0.008) presented higher initial TBS for CSA than for VAR. After aging, MH (p = 0.025) and VL (p = 0.034) cemented with VAR showed higher results than CSA. All tested groups showed very low TBS values. Pretreatments with MH, VL, and VP have minimally improved the tensile strength after aging. Although the tensile strength results were low, crowns adhesively cemented with pretreatments with MH, VL, and VP showed, after aging, a higher tensile strength than nontreated groups.

Experimental Study on the Effect of Different Pretreatment Methods on Rubber Concrete Work Performance and Compressive Strength

In untreated, clean water, NaOH solution to clean, CCl4solution to clean the rubber particles of different pretreatments as the main influencing factors, by 51 rubber concrete block pilot study reached different pretreatment methods on different rubber particle size and dosage of rubber concrete workability and compressive strength were investigated. The results show that: water, NaOH solution, CCl4pretreatment solution, such as a rubber concrete workability and compressive strength were improved, and the rubber particles larger pretreatment on rubber compressive strength of concrete work to improve performance and more obvious.

Effect of Different Pretreatment Methods on the Measurement of the Entrapment Efficiency of Liposomes and Countermeasures in Free Drug Analysis

Further investigation into the methods for the analysis of the entrapment efficiency of liposomes has been prompted by the urgent need to improve traditional methods which offer more risk to liposome leakage. The aim of this study was to investigate the suitability of hollow fiber centrifugal ultrafiltration (HF-CF-UF) coupled with HPLC as an alternative method for the routine determination of the entrapment efficiency of liposomes and to compare it with previously developed nonequilibrium procedures based on size-exclusion chromatography (SEC). By comparison, evaluation of the entrapped fraction with SEC resulted in 3 or 4 % lower entrapment values. More importantly, the free drug concentrations were three- to sixfold higher than with HF-CF-UF. In addition, we investigated the reasons for the different values obtained with SEC and a dynamic equilibrium theory was put forward based on this. In addition, we have developed and characterized an equilibrium method of separating free and liposomal drugs for liposomal formulations based on HF-CF-UF. The method was validated over the concentration range of 7.9–235 μg mL−1 for indomethacin and 0.258–8.24 μg mL−1 for vitamin A. Inter- and intra-day precision (RSD %) were ≤1.2 % for indomethacin and ≤1.8 % for vitamin A, respectively. The recoveries of both free drug and total drug were higher than 96.0 % with RSD ≤1.3 % (n = 5). Taken together, our improved method differs from those previously reported with regard to higher recovery, small sample volume, less laborious, and most importantly without damaging or disturbing liposomes. Validation results suggested that our method was sufficiently accurate and sensitive to be used to evaluate the entrapment efficiency of a liposome formulation without complicated pretreatment.

The Effect of Different Pretreatment Methods on the Membrane Fouling in the Process of Reverse Osmosis Seawater Desalination

One new pretreatment method was developed for solving the formed fouling on the equipments in the process of reverse osmosis seawater desalination, and the effect of different pretreatment methods on the membrane fouling was investigated. The experiment results showed that the flux attenuation rate of reverse osmosis membrane used in hardness-removed seawater was slower than the one of direct ultrafiltration seawater, and the salt reject rate and conductivity of output water from reverse osmosis membrane were not obviously affected by these two different pretreatment methods respectively. By according to the characterization of SEM, EDX and IR, the rapid attenuation of membrane flux was caused by the piled inorganic crystals on the membrane surface in direct ultra-filtration process, and the hardness-removed pretreatment process can effectively decrease the membrane fouling.

Altering protein conformation to improve fermentative hydrogen production from protein wastewater

One important reason for low hydrogen production from protein wastewater is due to the native folded conformation of protein. In this study the enhancement of bio-hydrogen production from protein wastewater by altering protein conformation via pretreatment was reported. Firstly, the effect of different pretreatment methods (acid, alkali, heat, and ultraviolet) on hydrogen production from synthetic protein wastewater was compared. The hydrogen production from the ultraviolet pretreated wastewater was 111.3 mL/g-protein, which was 3.79-, 3.73-, 3.54-, and 1.36-fold of that from the unpretreated (blank), acid, alkali, and heat pretreated wastewater, respectively. Then, the reasons for ultraviolet pretreatment showing significantly higher hydrogen production than other pretreatments were investigated. It was found that all pretreatments did not cause the cleavage of peptide bond, but the ultraviolet one caused much greater damage of hydrogen bonding networks and unfolding of protein. Thus, during anaerobic fermentation much higher protease activity and protein utilization were observed, which resulted in the bio-hydrogen production being remarkably improved. Further studies indicated that the photo-oxidization of aromatic residues in protein was not the reason for ultraviolet pretreatment remarkably improving bio-hydrogen production. Finally, the application of ultraviolet pretreatment to enhance hydrogen production from real protein wastewater was testified.

Chestnut Shell as Unexploited Source of Fermentable Sugars: Effect of Different Pretreatment Methods on Enzymatic Saccharification

Chestnut shell (CS) is an agronomic residue mainly used for extraction of antioxidants or as adsorbent of metal ions. It also contains some polysaccharide that has not been considered as potential source of fermentable sugars for biofuel production until now. In this study, the effect of different pretreatment methods on CS was evaluated in order to obtain the greatest conversion of cellulose and xylan into fermentable sugars. Hot acid impregnation, steam explosion (acid-catalysed or not), and aqueous ammonia soaking (AAS) were selected as pretreatments. The pretreated biomass was subjected to saccharification with two enzyme cocktails prepared from commercial preparations, and evaluation of the best pretreatment and enzyme cocktail was based on the yield of fermentable sugars produced. As AAS provided the best result after preliminary experiments, enhancement of sugar production was attempted by changing the concentrations of ammonium hydroxide, enzymes, and CS. The optimal pretreatment condition was 10 % ammonium hydroxide, 70 °C, 22 h with CS at 5 % solid loading. After saccharification of the pretreated CS for 72 h at 50 °C and pH 5.0 with a cocktail containing cellulase (Accellerase 1500), beta-glucosidase (Accellerase BG), and xylanase (Accellerase XY), glucose and xylose yields were 67.8 and 92.7 %, respectively.

Microbial community structure of anaerobic sludge for hydrogen production under different acid pretreatment conditions

The effect of different pretreatment methods on anaerobic H2 production from a sucrose-rich synthetic wastewater was investigated in this work. The substrate utilization, formation of aqueous products, H2 production and microbial diversity in anaerobic sludge all markedly depended on these pretreatment methods. The highest H2 production according to the values for the maximum H2 production rate of 27.57 ml h−1, specific H2 production rate of 2.962 ml g-VSS h−1, and H2 yield of 1.617 mol H2 mol glucose−1 was observed in the H2 production by the sludge pretreated with butyrate (pH = 2). Correspondingly, the main microbial communities were Clostridium sp. HPB-16, Clostridium sp. HPB-46, Clostridium sp. HPB-2, Clostridium sp. HPB-4, Oxalobacteraceae bacterium QD1, uncultured bacterium clone HPR93, uncultured Olsenella sp. clone J27, and uncultured bacterium clone SR_FBR_E5. This result demonstrates that acid pretreatment such as butyrate could be also as an effective method to enrich H2-producing bacteria from anaerobic sludge for large-scale biological H2 production.

A short review of improvement in flotation of low rank/oxidized coals by pretreatments

Low rank/oxidized coals are difficult to float with oily collectors. The presence of polar hydroxyl, carbonyl, phenol groups and some peroxide type oxygenated moieties on the surface of low rank/oxidized coals is the main factor which decreases the coal hydrophobicity. Pretreatments may be used to enhance the flotation of low rank/oxidized coals due to improved hydrophobicity. The primary methods of pretreatments are grinding, premixing/preconditioning, ultrasound, thermal, microwave and direct contact mixing of the reagents with dry coal before wetting. Among these pretreatment methods, grinding, premixing/preconditioning may be considered to remove the oxide layer on the oxidized coal surface, which is also reflected by ultrasound treatment. Thermal and microwave treatments are attributed to the removal of pore water, hydration water and some hydroxy functional groups in low rank/oxidized coals. Direct contact procedure makes the oxidized coal avoid the prevention for the collectors absorbing on the coal surface. The prevention usually comes from hydration shell on wet coal surface while the coal is wetted by water. This review is to highlight the effect of different pretreatment methods on the flotation of low rank/oxidized coals.

Bioconversion of Agricultural Waste to Ethanol by SSF Using Recombinant Cellulase fromClostridium thermocellum

The effect of different pretreatment methods, temperature, and enzyme concentration on ethanol production from 8 lignocellulosic agrowaste by simultaneous saccharification and fermentation (SSF) using recombinant cellulase and Saccharomyces cerevisiae were studied. Recombinant cellulase was isolated from E. coli BL21 cells transformed with CtLic26A-Cel5-CBM11 full-length gene from Clostridium thermocellum and produced in both batch and fed-batch processes. The maximum cell OD and specific activity in batch mode were 1.6 and 1.91 U/mg, respectively, whereas in the fed-batch mode, maximum cell OD and specific activity were 3.8 and 3.5 U/mg, respectively, displaying a 2-fold increase. Eight substrates, Syzygium cumini (jamun), Azadirachta indica (neem), Saracens indica (asoka), bambusa dendrocalmus (bamboo), Populas nigra (poplar), Achnatherum hymenoides (wild grass), Eucalyptus marginata (eucalyptus), and Mangifera indica (mango), were subjected to SSF. Of three pretreatments, acid, alkali, and steam explosion, acid pretreatment Syzygium cumini (Jamun) at 30°C gave maximum ethanol yield of 1.42 g/L.

Effect of different pretreatment methods on germination of Albizia julibrissin seeds

The seeds of Albizia julibrissin are dormant because of their hard seed coat and they need pretreatment in order to germinate. In this research the effect of a) dry heating, at 30°C to 100°C for 10 to 60 min, b) chemical scarification with concentrated H2SO4 for 15, 30, 60, 90 or 120 min, c) mechanical scarification for 5 sec, d) seed soaking in warm water (30°C to 100°C for one to six hours) and e) seed soaking in tap water for one to six days, on seed germination were examined. The most successful treatment was chemical scarification in concentrated H2SO4 for 2 hours (germination percentage 99%). Soaking in 40 or 50°C warm water also resulted in high germination percentages (86 and 91%). The germination obtained after soaking in tap water for two days was also satisfactory (73%). All the above treatments also increased the germination rate as the overall germination was completed in less than six weeks.

Comparative study of the effect of different pretreatment methods on biogas yield from water Hyacinth (Eichhornia Crassipes)

A comparative study of the effect of different pre-treatment methods on the biogas yield from Water Hyacinth (WH) was carried out. The WH charged into metallic prototype digesters of 121 L capacity were pre-treated as: dried and chopped alone (WH-A), dried and treated with KOH (WH-T), dried and combined with cow dung (WH-C), while the fresh water Hyacinth (WH-F) served as control. They were all subjected to anaerobic digestion to produce biogas for a 32 day retention period within a mesophilic temperature range of 25 to 36°C. The results of the study showed highest cumulative biogas yield from the WH-C with yield of 356.3 L/Total mass of slurry (TMS) while the WH-T had the shortest onset of gas flammability of 6 days. The mean biogas yield of the fresh Water Hyacinth (WH-F) was 8.48 ± 3.77 L/TMS. When the water Hyacinth was dried and chopped alone (WH-A), dried and treated with KOH (50% w/v) (WH-T) and dried and combined with cow dung (WH-C), the mean biogas yield increased to 9.75 ± 3.40 L/TMS, 9.51 ± 5.01 L/TMS and 11.88 ± L/TMS respectively. Flammable biogas was produced by the WH-F from the 10th day of the digestion period whereas the WH-A, WH-T and WH-C commenced flammable gas production from the 9th, 6th and 11th day respectively. Gas analysis from WH-F shows Methane (65.0%), CO2 (34.94%). WH- A contained Methane (60.0%), CO2 (39.94%). WH-T contained Methane (71.0%), CO2 (28.94%), while WH-C had Methane (64.0%) CO2 (35.94%). The other gases were found in the same levels and in trace amounts in all the systems. The overall results showed that treating water Hyacinth with chemical did not have a significant improvement on the biogas yield. It also indicated that water Hyacinth is a very good biogas producer and the yield can be improved by drying and combining it with Cow dung. Key words: Water hyacinth, biogas production, pre-treatment, biogas yield, flammable biogas production, biodigester.

Use of Carbon Mesh Anodes and the Effect of Different Pretreatment Methods on Power Production in Microbial Fuel Cells

Flat electrodes are useful in microbial fuel cells (MFCs) as close electrode spacing improves power generation. Carbon cloth and carbon paper materials typically used in hydrogen fuel cells, however, are prohibitively expensive for use in MFCs. An inexpensive carbon mesh material was examined here as a substantially less expensive alternative to these materials for the anode in an MFC. Pretreatment of the carbon mesh was needed to ensure adequate MFC performance. Heating the carbon mesh in a muffle furnace (450 degrees C for 30 min) resulted in a maximum power density of 922 mW/m2 (46 W/m3) with this heat-treated anode, which was 3% more power than that produced using a mesh anode cleaned with acetone (893 mW/ m2; 45 W/m3). This power density with heating was only 7% less than that achieved with carbon cloth treated by a high temperature ammonia gas process (988 mW/m2; 49 W/m3). When the carbon mesh was treated by the ammonia gas process, power increased to 1015 mW/m2(51 W/m3). Analysis of the cleaned or heated surfaces showed these processes decreased atomic O/C ratio, indicating removal of contaminants that interfered with charge transfer. Ammonia gas treatment also increased the atomic N/C ratio, suggesting that this process produced nitrogen related functional groups that facilitated electron transfer. These results show that low cost heat-treated carbon mesh materials can be used as the anode in an MFC, providing good performance and even exceeding performance of carbon cloth anodes.

Effect of Different Pretreatment Methods on Dentin Bond Strength of a One-step Self-etch Adhesive

The aim of this in vitro study was to evaluate the shear bond strength of a one-step self-etch adhesive to dentin pretreated with phosphoric acid, air abrasion, or laser. Fifty-six extracted non-carious human mandibular molars were mounted and the occlusal surfaces ground with a mechanical grinder to obtain flat occlusal dentin surfaces. The teeth were randomly divided into four groups of 14 teeth according to the different dentin surface pretreatment methods: Group I--acid, Group II--laser, Group III--air abrasion, Group IV (control)--no surface treatment. After applying a one-step self-etch adhesive system, Futura Bond NR, cylinders of Z250 composite resin were bonded to the dentin surfaces by transparent gelatin capsules (2.5 mm diameter; 3 mm high) and then polymerized. All specimens were stored in distilled water at 37 masculineC for 24 hours. Shear bond testing was carried out using an Universal testing machine with a crosshead speed of 0.5 mm/sec. Data were analyzed using the Kruskal Wallis and Mann-Whitney tests at a significance level of 0.05. The bond strength of air abrasion (Group III) and the control group (Group IV) were statistically higher than both the acid (Group I) and laser (Group II) pretreatments (p < 0.05). No statistically significant differences were found in shear bond strength between surfaces treated with air abrasion and the control group (p > 0.05). Surfaces pretreated with laser (Group II) resulted in the lowest bond strength which was not statistically different from those pretreated with acid (Group I) (p > 0.05). Surfaces pretreated with acid and laser adversely affected the bond strength of a one-step self-etch adhesive, Futura Bond NR, while pretreatment with air abrasion had no effect on bond strength. The pretreatment of dentin surfaces prior to self-etch adhesive seems to be unnecessary and defeats the original purpose of these systems.

Effect of Ultrasonic Waves on the Saccharification Processes of Lignocellulose

AbstractThe pretreatment and saccharification process of lignocellulose were subjected to ultrasonic waves to enhance the saccharification rate. The morphology, structure and crystal performance of the original and treated lignocellulose samples were characterized by SEM and FTIR. Moreover, the effect of different pretreatment methods on the structure of the raw materials and the influence of ultrasonic waves on the saccharification rate, were studied. SEM photographs show that the surface conformation of the granulated raw material is not changed, because the energy of the ultrasonic vibration is too low to cause changes to its structure. A FTIR spectrum shows that the ultrasonically assisted alkali pretreatment effectively destroys the intermolecular hydrogen bonding of lignocellulose and decreases its crystallinity. The catalytic efficiency of cellulase was increased by 70 % under ultrasonic treatment. Therefore, the ultrasonically assisted alkali pretreatment can improves the degradation rate of lignin and the saccharification rate of zymohydrolysis. The mechanism of the effect of ultrasonic waves on the enzymatic catalysis process is also discussed in detail.

Effect of Pretreatments on Drying Characteristics of Okra

This study was conducted to evaluate the effect of different pretreatment methods (blanching, microwave, and pulsed electric field [PEF]) on drying and rehydration behavior of okra. Drying rates were significantly (P < 0.05) influenced by the different pretreatments. The control samples had the lowest coefficient of diffusivity while samples pretreated with PEF at maximum energy input (4 kV/cm, 500 nF) had the highest coefficient. A simple exponential model used for describing the drying behavior of okra gave moisture diffusivity values ranging between 4.56 × 10−10 and 8.05 × 10−10 m2/s and the coefficient of determination values were between 0.94 and 0.98. Rehydration capacities of the control and pretreated samples were significantly different.

Effect of Different Pretreatment Methods on the Bioconversion of Rice Bran into Ethanol

The efficiency of acid, enzyme and microbial pretreatment of rice bran was compared based on the content of cellulose, hemicellulose, reducing sugars and xylose in the substrate. An isolate of Aspergillus niger or a strain of Trichoderma viride (MTCC 800) was employed for microbial pretreatment of rice bran in solid state. Acid pretreatment resulted in the highest amount of reducing sugars followed by enzyme and microbial pretreatment. A. niger showed a higher rate of hydrolysis than T. viride. The rice bran hydrolysate obtained from the different methods was subsequently fermented to ethanol either by Zymomonas mobilis (NCIM 806) or by Pichia stipitis (NCIM 3497). P stipitis fermentation resulted in higher ethanol (37% higher) and biomass production (76~83% higher) than those of Z. mobilis. Maximum ethanol production resulted at 12 h in Zymomonas fermentation, while in Pichia fermentation, it was observed at 60 h. Microbial pretreatment of rice bran by A. niger followed by fermentation employing P. stipitis was more efficient but slower than the other microbial pretreatment and fermentation.

Pyrolysis of sewage sludge: nitrogenated compounds and pretreatment effects

Pyrolysis at high temperature (850 °C) of different sewage sludge has been studied in a horizontal laboratory reactor. Volatile and semivolatile organic compounds from pyrolysis of seven different samples have been identified and quantified. Results show that yields of several compounds are similar to those obtained from other wastes in similar conditions. Nitrogenated aromatic compounds have been identified as characteristic compounds in sewage sludge pyrolysis due to their nitrogenous constitution. The origin and formation of these compounds are discussed. The effect of different pre-treatment methods of sewage sludge in the composition of pyrolysis gases has also been discussed.