Sequential Pretreatment Research Articles

Development of a steam or microwave-assisted sequential salt-alkali pretreatment for lignocellulosic waste: Effect on delignification and enzymatic hydrolysis

This study compares two different sequential pretreatments for sugarcane leaf waste (SLW): steam salt-alkali (SSA) and microwave salt-alkali (MSA). The two pretreatment types were modelled, optimized and validated with R2>0.97. Reducing sugar yields of 1.21g/g were obtained with optimized SSA pretreatment using 1.73M ZnCl2, 1.36M NaOH and 9.69% solid loading, and 1.17g/g with optimized MSA pretreatment using 1.67M ZnCl2, 1.52M NaOH at 400W for 10min. A lower pretreatment time (10min) was required for the MSA model (83% lower). The structure of pretreated SLW was assessed using scanning electron microscopy (SEM) and Fourier Transform Infrared analysis (FTIR). The optimized SSA and MSA models showed lignin removal of 80.5 and 73% respectively. The MSA pretreatment was further examined on sorghum leaves and Napier grass and showed yield improvements of 1.9- and 2.8-fold compared to recent reports. The developed pretreatment methods demonstrated high efficiency at enhancing enzymatic hydrolysis on various lignocellulosic substrates.

Microbial Lipid Production from Enzymatic Hydrolysate of Pecan Nutshell Pretreated by Combined Pretreatment.

Biodiesel is a fuel composed of monoalkyl esters of long-chain fatty acids derived from renewable biomass sources. In this study, biomass waste pecan nutshell (PS) was attempted to be converted into microbial oil. For effective utilization of PS, sequential pretreatment with ethylene glycol-H2SO4-water (78:2:20, wt:wt:wt) at 130°C for 30min and aqueous ammonia (25wt%) at 50°C for 24h was used to enhance its enzymatic saccharification. Significant linear correlation was obtained about delignification-saccharification (R 2=0.9507). SEM and FTIR results indicated that combination pretreatment could effectively remove lignin and xylan in PS for promoting its enzymatic saccharification. After 72h, the reducing sugars from the hydrolysis of 50g/L pretreated PS by combination pretreatment could be obtained at 73.6% yield. Using the recovered PS hydrolysates containing 20g/L glucose as carbon source, microbial lipids produced from the PS hydrolysates by Rhodococcus opacus ACCC41043. Four fatty acids including palmitic acid (C16:0; 23.1%), palmitoleic acid (C16:1; 22.4%), stearic acid (C18:0; 15.3%), and oleic acid (C18:1; 23.9%) were distributed in total fatty acids. In conclusion, this strategy has potential application in the future.

Two-step sequential pretreatment for the enhanced enzymatic hydrolysis of coffee spent waste

In the present study, eight different pretreatments of varying nature (physical, chemical and physico-chemical) followed by a sequential, combinatorial pretreatment strategy was applied to spent coffee waste to attain maximum sugar yield. Pretreated samples were analysed for total reducing sugar, individual sugars and generation of inhibitory compounds such as furfural and hydroxymethyl furfural (HMF) which can hinder microbial growth and enzyme activity. Native spent coffee waste was high in hemicellulose content. Galactose was found to be the predominant sugar in spent coffee waste. Results showed that sequential pretreatment yielded 350.12mg of reducing sugar/g of substrate, which was 1.7-fold higher than in native spent coffee waste (203.4mg/g of substrate). Furthermore, extensive delignification was achieved using sequential pretreatment strategy. XRD, FTIR, and DSC profiles of the pretreated substrates were studied to analyse the various changes incurred in sequentially pretreated spent coffee waste as opposed to native spent coffee waste.

Effects of Acid/Alkali and Cellulase Enriched Mixed Enzyme Treatments on Properties of Jute-Cotton Union Furnishing Fabric

The effects of chemical pre-treatments using dilute acids [HCl, CH3COOH, HCOOH, (CH2COOH)2C(OH)COOH] and alkali (NaOH) on raw jute and jute-cotton(75:25) union fabric and the effects of specified mixed enzyme system (different proportion of mixture of cellulase, xylanase and pectinase) pretreatment on conventional 2% H2O2 bleached jute-cotton union fabric have been comparatively evaluated. Among different organic/ mineral acid pretreatments 1% HCl treatment shows higher surface brightening action than that obtained by formic acid, acetic acid and citric acid pre-treatment. All these acid pretreatment do not show desirable softening action but show varying degree of surface leaching action associated with measurable changes in K/S value, whiteness, yellowness and brightness indices. However, 10-18 % NaOH pretreatment of raw jute-cotton union fabric show appreciable softening action but is associated with higher mass loss, appreciable reduction in tenacity and surface darkening. While, 5% dilute NaOH pretreatment show somewhat less softening action, but exhibit lower mass loss, lower surface darkening and lower reduction in tenacity which may be practically useful in imparting desirable softness in jute-cotton union fabric. Treatment with specified cellulase enriched mixed enzyme system (175 unit/ml of cellulase, 96 unit/ml of xylanase and 136 unit/ml of pectinase) on either 1 or 5% NaOH pretreated or conventional 2%H2O2 bleached jute-cotton union fabric renders a moderate degree of softening action and surface smoothening with overall good balance in important textile related properties. However, higher degree of softening action may be achieved, if the said mixed enzyme treatment is carried out after both sequential pretreatments i.e. 5% NaOH pretreatment followed by conventional H2O2 bleaching at the cost of higher weight loss and reduction in tenacity. Studies on Dyeability of such chemically treated jute-cotton union fabric reveals that NaOH pretreatment show an increasing trend for acid dye uptake and reactive dye uptake, while all the dilute acid pretreatments show an increasing trend of basic dye uptake in general.

The Detoxification of Heavy Metals in the Phosphate Tailing-contaminated Soil through Sequential Microbial Pretreatment and Electrokinetic Remediation

ABSTRACTIn this paper, the heavy metals (HMs) in the phosphate tailing-contaminated soil were detoxified using the microbial pretreatment in combination with electrokinetic remediation (EKR).. This study provides compelling evidence that the sequential usage of the bioleaching and electrokinetics is superior to the individual method for the detoxification of Pb, Cu, Zn, Cd, and As from the contaminated soil. In the sequential system, the detoxification efficiency of Zn was the highest and that of As was the lowest. Except the element As, the detoxification efficiencies of HMs in the sequential system were generally higher than that using the single biological treatment and EKR technique. Bioleaching, generation of the passivation, and migration direction of the ions are concluded as the factors attributable to the final results; and, the initial increase in the inoculation doping of Thiobacillus ferrooxidans considered has no obvious impact on improving the final detoxification efficiency rates.

Characterization of the Micromorphology and Topochemistry of Poplar Wood during Mild Ionic Liquid Pretreatment for Improving Enzymatic Saccharification.

Ionic liquids (ILs) as designer solvents have been applied in biomass pretreatment to increase cellulose accessibility and therefore improve the enzymatic hydrolysis. We investigated the characterization of the micromorphology and the topochemistry of poplar wood during 1-ethyl-3-methylimidazolium acetate pretreatment with mild conditions (90 °C for 20 and 40 min) by multiple microscopic techniques (FE-SEM, CLSM, and CRM). Chemical composition analysis, XRD, cellulase adsorption isotherm, and enzymatic hydrolysis were also performed to monitor the variation of substrate properties. Our results indicated that the biomass conversion was greatly enhanced (from 20.57% to 73.64%) due to the cell wall deconstruction and lignin dissolution (29.83% lignin was removed after incubation for 40 min), rather than the decrystallization or crystallinity transformation of substrates. The mild ILs pretreatment, with less energy input, can not only enhance enzymatic hydrolysis, but also provide a potential approach as the first step in improving the sequential pretreatment effectiveness in integrated methods. This study provides new insights on understanding the ILs pretreatment with low temperature and short duration, which is critical for developing individual and/or combined pretreatment technologies with reduced energy consumption.

Alkaline deacetylation as a strategy to improve sugars recovery and ethanol production from rice straw hemicellulose and cellulose

A mild alkaline pretreatment (deacetylation) prior to the dilute acid pretreatment was evaluated as a strategy to improve the sugars recovery and ethanol production from both hemicellulose and cellulose fractions of rice straw. This pretreatment was carried out using different conditions of temperature (50–70°C) and NaOH loading (20–80mg NaOH/g biomass), which were combined according to a 22 central composite design. In this step the removal of acetyl groups as well as the impact of this step on biomass composition were evaluated. In order to assess the impact of the deacetylation on hemicellulosic hydrolysate composition, the influence of the reaction time (30–90min) and sulfuric acid concentration (0.5–1.5% w/v) was also studied, using the alkaline-pretreated solid (deacetylated) and rice straw in natura. The best sequential pretreatment conditions were scaled-up to 50-L reactor, being obtained a cellulose-rich pretreated solid (cellulignin) and a hemicellulosic hydrolysate, which was concentrated to 70g/L xylose to be used as fermentation medium. A significant improvement on ethanol production from xylose by Scheffersomyces stipitis NRRL Y-7124 was observed when the biomass was submitted to deacetylation (about 4-fold). The enzymatic conversion of cellulose was also improved (from 73 to 89%) when the deacetylated cellulignin was used, resulting in an enhancement of the ethanol production (from 12.7 to 20.4g/L) during the simultaneous saccharification and fermentation with Kluyveromyces marxianus NRRL Y-6860. In brief, biomass deacetylation prior to dilute acid pretreatment was an efficient strategy for rice straw processing, substantially improving the ethanol production from both pentose and hexose sugars.

Combining Coagulation/MIEX with Biological Activated Carbon Treatment to Control Organic Fouling in the Microfiltration of Secondary Effluent.

Coagulation, magnetic ion exchange resin (MIEX) and biological activated carbon (BAC) were examined at lab scale as standalone, and sequential pre-treatments for controlling the organic fouling of a microfiltration membrane by biologically treated secondary effluent (BTSE) using a multi-cycle approach. MIEX gave slightly greater enhancement in flux than coagulation due to greater removal of high molecular weight (MW) humic substances, although it was unable to remove high MW biopolymers. BAC treatment was considerably more effective for improving the flux than coagulation or MIEX. This was due to the biodegradation of biopolymers and/or their adsorption by the biofilm, and adsorption of humic substances by the activated carbon, as indicated by size exclusion chromatography. Coagulation or MIEX followed by BAC treatment further reduced the problematic foulants and significantly improved the flux performance. The unified membrane fouling index showed that the reduction of membrane fouling by standalone BAC treatment was 42%. This improved to 65%, 70%, and 93% for alum, ferric chloride and MIEX pre-treatment, respectively, when followed by BAC treatment. This study showed the potential of sequential MIEX and BAC pre-treatment for controlling organic fouling and thus enhancing the performance of microfiltration in the reclamation of BTSE.

Sequential extrusion-ozone pretreatment for the production of bioethanol by Pichia stipitis from wheat straw

Sequential extrusion-ozone pretreatment for the production of bioethanol by Pichia stipitis from wheat straw

Mixed Lignocellulosic Biomass Degradation and Utilization for Bacterial Cellulase Production

Feedstock supply challenges provide impetus into the exploration of lignocellulosic mixtures in bioprocessing. Such mixtures have not been fully explored for bacterial cellulase production. Four bacterial species were evaluated for ability to utilize a mixture of oil palm and rice residues (MS) for cellulase production. Bacillus aerius, Bacillus anthracis, Cellvibrio japonicus and Klebsiella pneumoniae with ability to utilize MS for growth were investigated. A two-step sequential strategy was employed in selecting the candidate for cellulase production and degradation of MS. B. aerius displayed better cellulolytic ability than the others during plate screening on carboxymethyl cellulose-enriched medium. However, C. japonicus produced the highest activities of endoglucanase and total cellulase during targeted screening on MS. Analyses revealed that sequential pretreatment with NaOH and moist heat increased the accessibility and disrupted the surface morphology of MS for subsequent bacterial utilisation. C. japonicus achieved significant degradation of MS with 52.33 % substrate dry weight loss after 7 days as compared to B. aerius which degraded 21.33 % of MS in the same period. Substrate was hydrolyzed via the amorphous region. The low residual concentration of reducing sugars in the medium suggested that C. japonicus converted the liberated sugars into other products.

Enhancing enzymolysis and fermentation efficiency of sugarcane bagasse by synergistic pretreatment of Fenton reaction and sodium hydroxide extraction

A study on the synergistic pretreatment of sugarcane bagasse (SCB) using Fenton reaction and NaOH extraction was conducted. The optimized process conditions for Fenton pretreatment were 10% (w/w) of H2O2, 20mM of Fe2+, pH 2.5, pretreatment time 6h, and pretreatment temperature 55°C. Sequential pretreatments were performed in combination with NaOH extraction (NaOH 1% (w/w), 80°C, 5% of solid loading, 1h). Among all the pretreatments, Fenton pretreatment followed by NaOH extraction had the highest efficiency of 64.7% and 108.3% for enzymolysis and simultaneous saccharification fermentation (SSF) with an ethanol concentration of 17.44g/L. The analyses by the scanning electron microscopy, X-ray diffraction and confocal laser scanning microscopy revealed that Fenton pretreatment disrupts the structure of SCB to facilitate the degradation of lignin by NaOH. The overall data suggest that this combinatorial strategy is a promising process for SCB pretreatment.

Development of a novel sequential pretreatment strategy for the production of bioethanol from sugarcane trash

A novel sequential pretreatment strategy using biodiesel industry generated waste glycerol assisted transition metal and alkali pretreatment of sugarcane trash were developed for the production of bioethanol. Various process parameters affecting pretreatment as well as hydrolysis were optimized by adopting a Taguchi design. This novel method was found to be superior when compared to conventional pretreatment strategies like acid and alkali in removing hemicelluloses and lignin and the hydrolyzate is devoid of major fermentation inhibitors like organic acids and furfurals. Physico-chemical changes of the native and the pretreated biomass were evaluated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analysis. Under optimized hydrolysis conditions 0.796g of reducing sugar (pentoses and hexoses) per g of dry biomass after saccharification was produced. Fermentation of the non-detoxified hydrolyzate using Saccharomyces cerevisiae produced 31.928g of bioethanol per g of dry biomass with an efficiency of 78.89%.

Impact of Sequential Ammonia Fiber Expansion (AFEX) Pretreatment and Pelletization on the Moisture Sorption Properties of Corn Stover

Combining ammonia fiber expansion (AFEX™) pretreatment with a depot processing facility is a promising option for delivering high-value densified biomass to the emerging bioenergy industry. However, because the pretreatment process results in a high moisture material unsuitable for pelleting or storage (40% wet basis), the biomass must be immediately dried. If AFEX pretreatment results in a material that is difficult to dry, the economics of this already costly operation would be at risk. This work tests the nature of moisture sorption isotherms and thin-layer drying behavior of corn (Zea mays L.) stover at 20°C to 60°C before and after sequential AFEX pretreatment and pelletization to determine whether any negative impacts to material drying or storage may result from the AFEX process. The equilibrium moisture content to equilibrium relative humidity relationship for each of the materials was determined using dynamic vapor sorption isotherms and modeled with modified Chung-Pfost, modified Halsey, and modified Henderson temperature-dependent models as well as the Double Log Polynomial (DLP), Peleg, and Guggenheim Anderson de Boer (GAB) temperature-independent models. Drying kinetics were quantified under thin-layer laboratory testing and modeled using the Modified Page's equation. Water activity isotherms for non-pelleted biomass were best modeled with the Peleg temperature-independent equation while isotherms for the pelleted biomass were best modeled with the Double Log Polynomial equation. Thin-layer drying results were accurately modeled with the Modified Page's equation. The results of this work indicate that AFEX pretreatment results in drying properties more favorable than or equal to that of raw corn stover, and pellets of superior physical stability in storage.

Abstract T P5: Sequential and Post-procedure ASPECTS Predict Clinical Outcome in Mechanical Thrombectomy of Acute Anterior Circulation Ischemic Stroke

Purpose: Final ASPECTS has been shown to predict patient outcomes after endovascular therapy in stroke. The goal of this study was to compare sequential ASPECTS imaging pre-treatment and post-treatment in predicting outcome. Methods: The PICS Study is a prospective registry of clinical and imaging data in proximal artery occlusion patients treated with the Penumbra System. In multivariate analysis, variables assessed for relationship to 90 day mRS included age, gender, time to reperfusion, occlusion location, ASPECTS, and NIHSS. ASPECTS scores were assessed by a central core laboratory, blinded except for stroke side. Results: In this study, 141 patients with mean age 67.9 ± 15.6 and median admission NIHSS score 16.0 (IQR 12.0-21.0) met study criteria. Univariate predictors of 90 day mRS included age, baseline NIHSS, 7 day/discharge NIHSS as well as post-treatment ASPECTS. After adjusting for age and baseline NIHSS, post procedure ASPECTS showed a stronger relationship with good outcome (p<0.0001) than pre-treatment ASPECTS (p=0.0520). Change in ASPECTS was also a significant predictor of 90 day mRS (p=0.0046) in the multivariate analysis. Conclusion: Sequential and post procedure ASPECTS are better predictors of clinical outcome following endovascular therapy than pre-ASPECTS. Final infarct volume quantified using ASPECTS serves as a surrogate biomarker for long-term functional outcome.

Sequential pretreatment strategies under mild conditions for efficient enzymatic hydrolysis of wheat straw.

This work studies the sequential execution of dilute sulfuric acid (DAP) (0.1-0.75 %, v/v) and dilute sodium hydroxide (AKP) (0.25-3 %, w/v) [i.e., DAP followed by AKP (DAP+AKP) and vice versa (AKP+DAP)] at low temperatures (<121 °C) and short reaction times (5-60 min) for maximizing sugar recovery in the enzymatic hydrolysis of wheat straw with low enzyme dosage. The pretreatment effectiveness was measured by the sum of the severity factors of both pretreatments and the saccharification yield achieved in the subsequent stage of enzymatic hydrolysis. Degradation compounds were quantified and mass balance calculations were carried out for each pretreatment sequence to verify the correct account of the input biomass and output products. Results show that sequential pretreatments (AKP+DAP and DAP+AKP) had a positive effect in enzyme accessibility thus improving monosaccharide yields compared to single DAP and AKP pretreatments. DAP+AKP achieved a high xylose yield (ca. 0.867 of theoretical) at the DAP stage, while no xylose monosaccharides were detected in the subsequent AKP. After enzyme saccharification of double-pretreated solids, the total monosaccharide yield was 0.786 (of theoretical). For AKP+DAP sequence, lower results were obtained (total monosaccharide yield 0.783 of theoretical). Sequential pretreatments total yields increased by 21 % compared to single pretreatments. AKP removed more than half of the lignin from the wheat straw in all cases. Acid and alkali concentrations played a relevant role in all pretreatment sequences, while reaction time and temperature were less important with an almost-linear effect on the total monosaccharide yields.

Sequential Extrusion-Ozone Pretreatment of Switchgrass and Big Bluestem

Pretreatment is one of the biggest challenges in utilizing lignocellulosic feedstocks to meet the mandatory requirements for biofuels around the world. Earlier researchers evaluated extrusion and ozone pretreatment separately and found that sugar recovery can be improved significantly from 15-20 to 40-75% for different feedstocks. To further improve sugar recoveries, extrusion-ozone sequential pretreatment was explored. Accordingly, optimal extruded switchgrass (176 °C, 155rpm, 20% moisture, and 8mm) and big bluestem (180 °C, 155rpm, 20% moisture, and 8mm) at 25-75% moisture content were exposed to an ozone flow rate of 37-365mg/h for 2.5 to 10min. Pretreated samples were then subjected to enzymatic hydrolysis to determine sugar recovery. Statistical analyses confirmed significant effects of the independent variables and their interactions on sugar recoveries for both feedstocks. Maximum glucose, xylose, and total sugar recovery of 66.4, 82.3, and 70.4%, respectively, were obtained when a low-moisture (25%) extruded switchgrass was ozonated for 2.5min at a flow rate of 37mg/h. Respectively, this represents increases of 3.42, 5.01, and 3.42 times that of the control. When big bluestem at 25% moisture was extruded and then ozonated for 2.5min at a flow rate of 365mg/h, resulting glucose, xylose, and total sugar recoveries of 90.8, 92.2, and 87.5%, respectively, were obtained. These represent increases of 4.5, 2.7, and 3.9 times than that of the control. It is also noteworthy that furfural and hydroxymethyl furfural were not detected in any of the pretreatments, and only low levels (0.14-0.18g/l) of acetic acid were measured. The results show that sequential pretreatment using extrusion and ozone is an efficient way to improve sugar recovery from herbaceous biomass feedstocks.

Sequential extrusion-microwave pretreatment of switchgrass and big bluestem

Developing an effective and economical biomass pretreatment method is a significant roadblock to meeting the ever growing demand for transportation fuels. Earlier studies with different feedstocks revealed that in the absence of chemicals, neither extrusion nor microwave could be standalone pretreatments. However, there is potential that the advantages of these individual methods can be harnessed in a sequential pretreatment process. Accordingly, switchgrass and big bluestem were extruded and then subject to microwave pretreatment, under optimal conditions that had been separately determined in prior studies. Pretreated biomass was then subject to enzymatic hydrolysis to understand the effectiveness of the sequential pretreatment on sugar recovery and generation of fermentation inhibitors. Statistical analysis confirmed that moisture content, microwave power level, and exposure time (and their interactions) had significant influence on sugar recovery. Sequential pretreatment of switchgrass (25% moisture, 450W and 2.5min) resulted in a maximum glucose, xylose, and total sugar recovery of 52.6%, 75.5%, and 59.2%, respectively. This was higher by 1.27 and 2.71, 1.21 and 4.60, and 1.25 and 2.87 times compared to extrusion alone and the unpretreated control, respectively. The same sequential pretreatment conditions achieved maximum glucose, xylose, and total sugar recovery of 83.2%, 92.1%, and 68.1%, respectively, for big bluestem. This was 1.14 and 4.1, 1.18 and 2.7, and 1.20 and 3.0 times higher than extrusion alone and the unpretreated control, respectively. This sequential pretreatment process did not aggravate acetic acid formation over levels observed with the individual pretreatments. Furthermore, furfural, HMF, and formic acid were not detected in any of the treatments. Although the sequential pretreatment process enhanced sugar recovery without increasing the levels of potential fermentation inhibitors, the increased energy input for the microwave treatment may not be economical.

Separation and purification of carbon nanotubes using froth flotation with three sequential pretreatment steps of catalyst oxidation, catalyst removal, and silica dissolution

ABSTRACTCarbon nanotubes (CNTs) with a carbon content of 3% were synthesized via the disproportionation of CO over a CoMo/SiO2 catalyst. The proposed purification technique consisted of four sequential steps: oxidative treatment, acid leaching, silica dissolution, and froth flotation. The as‐synthesized CNTs were oxidized at 250 °C before being treated with a 5‐m HCl solution at 80 °C and a sonication time of 6 h, resulting in a catalyst removal of 90% and an increase in carbon content to 4%. For the silica dissolution, the CNTs were treated with a 0.5‐m NaOH solution at 70 °C and a sonication time of 12 h, leading to a silica removal of 70% and an increase in carbon content to 35%. The froth flotation technique was employed to separate the CNTs from the remaining silica using two types of surfactants: linear ethoxylated alcohol with an average degree of polymerization of 7 and a linear alkyl chain of 12–14 carbon number (Surfonic L24‐7) and sodium dodecyl benzene sulfonate (SDBS). The separation performance was maximized at a Surfonic L24‐7‐to‐SDBS molar ratio of 1 : 12 with a total surfactant concentration of 230 mg/L, yielding a carbon content of 76%. © 2013 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

A novel bioluminescent bacterial biosensor for measurement of Ara-CTP and cytarabine potentiation by fludarabine in seven leukaemic cell lines

This study evaluates an in vitro biosensor assay capable of detecting the intracellular levels of the tri-phosphorylated form of cytarabine (Ara-CTP) within one working day. The biosensor predicted the response of seven leukaemic cell lines with varying known sensitivities to cytarabine alone and in combination with fludarabine. High-performance liquid chromatography (HPLC), 3-day assessment of cellular viable mass, and flow cytometric assessment of apoptosis were used to validate biosensor performance. A correlation between the biosensor results and Ara-CTP quantitation by HPLC was confirmed (R=0.972). The biosensor was also capable of detecting enhanced accumulation of Ara-CTP following sequential pre-treatment of leukaemic cells with cytarabine±fludarabine.

Sequential Acid-Base Pretreatment of Sugarcane Bagasse: A Facile Method for the Sugars Recovery After Enzymatic Hydrolysis

Sequential Acid-Base Pretreatment of Sugarcane Bagasse: A Facile Method for the Sugars Recovery After Enzymatic Hydrolysis