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The influence of solid/liquid separation techniques on the sugar yield in two-step dilute acid hydrolysis of softwood followed by enzymatic hydrolysis
Sanam Monavari, Mats Galbe, Guido Zacchi
Biotechnology for Biofuels , 2009, DOI: 10.1186/1754-6834-2-6
Abstract: Washing the material between the two acid hydrolysis steps, followed by enzymatic digestion, resulted in recovery of 96% of the mannose and 81% of the glucose (% of the theoretical) in the liquid fraction, regardless of the choice of dewatering method (pressing or vacuum filtration). Not washing the solids between the two acid hydrolysis steps led to elevated acidity of the remaining solids during the second hydrolysis step, which resulted in lower yields of mannose, 85% and 74% of the theoretical, for the pressed and vacuum-filtered slurry, respectively, due to sugar degradation. However, this increase in acidity resulted in a higher glucose yield (94.2%) from pressed slurry than from filtered slurry (77.6%).Pressing the washed material between the two acid hydrolysis steps had no significant negative effect on the sugar yields of the second acid hydrolysis step or on enzymatic hydrolysis. Not washing the material resulted in a harsher second acid hydrolysis step, which caused greater degradation of the sugars during subsequent acid hydrolysis of the solids, particularly in case of the vacuum-filtered solids. However, pressing in combination with not washing the material between the two steps enhanced the sugar yield of the enzymatic digestion step. Hence, it is suggested that the unwashed slurry be pressed to as high a dry matter content as possible between the two acid hydrolysis stages in order to achieve high final sugar yields.Interest in ethanol as an alternative fuel is increasing. Bioethanol is not only an attractive substitute for oil, but it also has positive effects on the environment, such as low net carbon dioxide emission. Unlike fossil fuels, ethanol is a renewable energy source, and can be produced from lignocellulosic biomass. Lignocellulosic materials are an attractive feedstock because they are available in large quantities [1,2]. In Sweden, Canada and parts of the USA softwood (pine and spruce) may become the major renewable source of ethanol pr
Jiebin Tang,Kefu Chen,Jun Xu,Jun Li
BioResources , 2011,
Abstract: Dilute sulfuric acid hydrolysis was performed before the isolation of cellulose from Eulaliopsis binata. And then, the effects of dilute acid hydrolysis on composition and structure of the cellulose was studied in detail. The results indicated that hemicellulose was dissolved mostly and that the lignin-hemicellulose-cellulose interactions were also partially disrupted during the dilute acid hydrolysis. Cellulose in Eulaliopsis binata was identified as the cellulose I allomorph with low crystallinity. What’s more, hydrolysis with dilute acid at high temperature increased the degree of cellulose crystallinity and relatively reduced the proportions of less ordered cellulose allomorphs. This was attributed to a preferential degradation of amorphous cellulose and less ordered crystalline forms during the hydrolysis. The cellulose preparation from Eulaliopsis binata after dilute acid hydrolysis had a higher thermal stability than the cellulose preparation from untreated Eulaliopsis binata.
Co-hydrolysis of hydrothermal and dilute acid pretreated populus slurries to support development of a high-throughput pretreatment system
Michael H Studer, Simone Brethauer, Jaclyn D DeMartini, Heather L McKenzie, Charles E Wyman
Biotechnology for Biofuels , 2011, DOI: 10.1186/1754-6834-4-19
Abstract: For hydrothermal pretreatment at solids concentrations of 0.5 to 2%, high enzyme protein loadings of about 100 mg/g of substrate (glucan plus xylan) in the original poplar wood achieved glucose and xylose yields for co-hydrolysis that were comparable with those for washed solids. In addition, although poplar wood sugar yields from co-hydrolysis at 2% solids concentrations fell short of those from hydrolysis of washed solids after dilute sulfuric acid pretreatment even at high enzyme loadings, pretreatment at 0.5% solids concentrations resulted in similar yields for all but the lowest enzyme loading.Overall, the influence of severity on susceptibility of pretreated substrates to enzymatic hydrolysis was clearly discernable, showing co-hydrolysis to be a viable approach for identifying plant-pretreatment-enzyme combinations with substantial advantages for sugar production.The BioEnergy Science Center (BESC) addresses the challenge of reducing the recalcitrance of biomass, the dominant obstacle to cost-effective production of biofuels, by engineering of plants together with development of advanced biocatalysts to reduce recalcitrance and improve deconstruction [1]. Recent advances in plant genomics have led to large and diverse genome libraries of plant species that can improve our understanding of how individual plant species perform in ethanol-production processes to help guide future development of feedstocks with potentially advantageous characteristics for cellulosic ethanol production. Because reliable methods to characterize recalcitrance of plant cell walls to saccharification do not yet exist, identification of superior biomass species for ethanol production necessitates screening deconstruction of lignocellulosic biomass by pretreatment and subsequent enzymatic hydrolysis. However, final sugar yields depend not only on biomass characteristics but also on their interaction with pretreatment conditions and enzyme formulations. Furthermore, pretreatment is not a
Shuangning Xiu,Yuanhui Zhang,Abolghasem Shahbazi
BioResources , 2009,
Abstract: Separation of solids from liquid swine manure and subsequent thermo-chemical conversion (TCC) of the solids fraction into oil is one way of reducing the waste strength and odor emission. Such processing also provides a potential means of producing renewable energy from animal wastes. Gravity settling and mechanical separation techniques, by means of a centrifuge and belt press, were used to remove the solids from liquid swine manure. The solid fractions from the above separation processes were used as the feedstock for the TCC process for oil production. Experiments were conducted in a batch reactor with a steady temperature 305 oC, and the corresponding pressure was 10.34 Mpa. Gravity settling was demonstrated to be capable of increasing the total solids content of manure from 1% to 9%. Both of the mechanical separation systems were able to produce solids with dry matter around 18% for manure, with 1% to 2% initial total solids. A significant amount of volatile solid (75.7%) was also obtained from the liquid fraction using the belt press process. The oil yields of shallow pit manure solids and deep pit manure solids with belt press separation were 28.72% and 29.8% of the total volatile solids, respectively. There was no visible oil product obtained from the deep pit manure solids with centrifuge separation. It is believed that it is the volatile solid content and the other components in the manure chemical composition which mainly deter-mine the oil production.
Evaluation of Chemically Coagulated Swine Manure Solids as Value-Added Products  [PDF]
Sammy Sadaka, Karl Van Devender
Journal of Sustainable Bioenergy Systems (JSBS) , 2015, DOI: 10.4236/jsbs.2015.54013

The objective of this research was to evaluate the chemically coagulated swine manure solids as biofuel and/or compost feedstock. Three coagulants, namely agricultural lime [CaCO3], hydrated lime [Ca(OH)2], and lime slurry [Ca(OH)2], were added to fresh swine manure to coagulate manure solids. Four levels, i.e., 0.00 (0.0X), 4.89 (0.5X), 9.77 (1.0X), and 19.77 (2.0X) gm Ca⋅liter-1, were tested, in triplicates. Increasing the coagulant concentration increased the total solids, ash content, and pH of solid manure samples, whereas it decreased their volatile solids, chemical oxygen demand, and heating value. At the coagulant level of 2.0X rate, heating values of samples coagulated by agricultural lime, hydrated lime, and lime slurry were 2.64, 4.48, and 4.54 MJ⋅kg-1, respectively. The heating value of raw manure solids was as high as 13.49 MJ⋅kg-1. Increasing the coagulant concentration increased the O/C atomic ratio for all the studied coagulants. Accordingly, the high coagulant concentrations might reduce the acceptability of the feedstock as a biofuel that can be co-combusted with other feed stocks. The C/N ratio and the pH values of the solid separated swine manure increased by increasing agricultural lime and hydrated lime concentrations. The former might increase satisfactoriness for composting these solids, whereas the latter might hinder their use in the composting process. The maximum coagulant concentrations that allowed pyrolyzing the final product, based on the net energy values, were 48.80 (2.0X), 18.06 (1.0X), and 18.06 (1.0X) gm⋅liter-1 for agricultural lime, hydrated lime, and lime slurry, respectively. The maximum acceptable coagulant concentrations that allowed composting the final product, based on the pH values, were 48.80 (2.0X), 0.00 (0.0X), and 9.03 (0.5X) gm⋅liter-1 for the same three coagulants.

Farid Talebnia,Mohammad Pour Bafrani,Magnus Lundin,Mohammad Taherzadeh
BioResources , 2008,
Abstract: The effect of time, acid concentration, temperature and solid concentration on dilute-acid hydrolysis of orange peels was investigated. A central composite rotatable experimental design (CCRD) was applied to study the individual effects of these hydrolysis factors and also their interdependence effects. The enzymatic hydrolysis of the peels by cellulase, β-glucosidase, and pectinase enzyme resulted in 72% dissolution of the peels, including 18.7% galacturonic acid and 53.3% of a total of glucose, fructose, galactose, and arabinose. Dilute-acid hydrolysis up to 210°C was not able to hydrolyze pectin to galacturonic acid. However, the sugar polymers were hydrolyzed at relatively low temperature. The optimum results were obtained at 116°C, 0.5% sulfuric acid concentration, 6% solid fraction, and 12.9 min retention time. Under these conditions, the total sugars obtained at 41.8 g/g dry peels and 2.6% of total hexose sugars were further degraded to hydroxymethylfurfural (HMF). No furfural was detected through these experiments from decomposition of pentoses.
Study of Enzymatic Hydrolysis of Dilute Acid Pretreated Coconut Husk  [cached]
Rudy Agustriyanto,Akbarningrum Fatmawati,Yusnita Liasari
Bulletin of Chemical Reaction Engineering & Catalysis , 2012, DOI: 10.9767/bcrec.7.2.4046.137-141
Abstract: Coconut husk is classified as complex lignocellulosic material that contains cellulose, hemicellulose, lignin, and some other extractive compounds. Cellulose from coconut husk can be used as fermentation substrate after enzymatic hydrolysis. In contrary, lignin content from the coconut husk will act as an inhibitor in this hydrolysis process. Therefore, a pretreatment process is needed to enhance the hydrolysis of cellulose. The objective of this research is to investigate the production of the glucose through dilute acid pretreatment and to obtain its optimum operating conditions. In this study, the pretreatment was done using dilute sulfuric acid in an autoclave reactor. The pretreatment condition were varied at 80 C, 100 C, 120 C and 0.9%, 1.2%, 1.5% for temperature and acid concentration respectively. The acid pretreated coconut husk was then hydrolyzed using commercial cellulase (celluclast) and β-glucosidase (Novozyme 188). The hydrolysis time was 72 hours and the operating conditions were varied at several temperature and pH. From the experimental results it can be concluded that the delignification temperature variation has greater influence than the acid concentration. The optimum operating condition was obtained at pH 4 and 50 C which was pretreated at 100 C using 1.5% acid concentration. Copyright 2012 by BCREC UNDIP. All rights reserved. (Selected Paper from International Conference on Chemical and Material Engineering (ICCME) 2012) Received: 28th September 2012, Revised: 2nd October 2012, Accepted: 4th October 2012 [How to Cite: R. Agustriyanto, A. Fatmawati, Y. Liasari. (2012). Study of Enzymatic Hydrolysis of Dilute Acid Pretreated Coconut Husk. Bulletin of Chemical Reaction Engineering & Catalysis, 7(2): 137-141. doi:10.9767/bcrec.7.2.4046.137-141] [How to Link / DOI: http://dx.doi.org/10.9767/bcrec.7.2.4046.137-141 ] | View in
Yield-determining factors in high-solids enzymatic hydrolysis of lignocellulose
Jan B Kristensen, Claus Felby, Henning J?rgensen
Biotechnology for Biofuels , 2009, DOI: 10.1186/1754-6834-2-11
Abstract: The decreasing conversion at increasing solids concentrations was found to be a generic or intrinsic effect, describing a linear correlation from 5 to 30% initial total solids content (w/w). Insufficient mixing has previously been shown not to be involved in the effect. Hydrolysis experiments with filter paper showed that neither lignin content nor hemicellulose-derived inhibitors appear to be responsible for the decrease in yields. Product inhibition by glucose and in particular cellobiose (and ethanol in simultaneous saccharification and fermentation) at the increased concentrations at high solids loading plays a role but could not completely account for the decreasing conversion. Adsorption of cellulases was found to decrease at increasing solids concentrations. There was a strong correlation between the decreasing adsorption and conversion, indicating that the inhibition of cellulase adsorption to cellulose is causing the decrease in yield.Inhibition of enzyme adsorption by hydrolysis products appear to be the main cause of the decreasing yields at increasing substrate concentrations in the enzymatic decomposition of cellulosic biomass. In order to facilitate high conversions at high solids concentrations, understanding of the mechanisms involved in high-solids product inhibition and adsorption inhibition must be improved.Climate changes and shortage of fossil fuels have sparked a growing demand for liquid biofuels which in turn has increased the amount of research into the production of lignocellulose-derived bioethanol [1,2]. However, being an insoluble and highly heterogeneous substrate, lignocellulosic materials pose several challenges in conversion to fermentable sugars. In addition to understanding complex enzyme system kinetics, these biomass-related challenges include recalcitrance to hydrolysis [3] and mixing difficulties [4]. Water content in the hydrolysis slurry is directly correlated to rheology, that is, viscosity and shear rate during mixing [5],
Hamzeh Hoseinpour,Keikhosro Karimi,Hamid Zilouei,Mohammad J. Taherzadeh
BioResources , 2010,
Abstract: Mixtures of starch and lignocelluloses are available in many industrial, agricultural, and municipal wastes and residuals. In this work, dilute sulfuric acid was used for simultaneous pretreatment of lignocellulose and hydrolysis of starch, to obtain a maximum amount of fermentable sugar after enzymatic hydrolysis with cellulase and β-glucosidase. The acid treatment was carried out at 70-150°C with 0-1% (v/v) acid concentration and 5-15% (w/v) solids concentration for 0-40 minutes. Under the optimum conditions, obtained at 130°C, 1% acid, and 7.5% solids loading for 30 min, the starch was almost completely converted to glucose. However, the acid treatment was not successful for efficient hydrolysis of pure cellulose. A mixture of pine softwood and potato as representatives of lignocellulosic and starch components, respectively, were treated at the optimum conditions for acid hydrolysis of starch. The dilute-acid treatment resulted in 1.2, 60.5, and 23.6% hydrolysis of glucan, xylan, and mannan of pine wood and 67% of potato starch to fermentable sugars. After the acid treatment, the solid residue of the mixture was subjected to enzymatic hydrolysis. The enzymatic hydrolysis under the optimum conditions resulted in conversion of 76% of the glucan in the treated softwood. Therefore, using acid treatment of the mixture is a promising process for pretreatment of wood in addition to the hydrolysis of starch.
Enzymatic lignocellulose hydrolysis: Improved cellulase productivity by insoluble solids recycling  [cached]
Weiss Noah,B?rjesson Johan,Pedersen Lars Saaby,Meyer Anne S
Biotechnology for Biofuels , 2013, DOI: 10.1186/1754-6834-6-5
Abstract: Background It is necessary to develop efficient methods to produce renewable fuels from lignocellulosic biomass. One of the main challenges to the industrialization of lignocellulose conversion processes is the large amount of cellulase enzymes used for the hydrolysis of cellulose. One method for decreasing the amount of enzyme used is to recycle the enzymes. In this study, the recycle of enzymes associated with the insoluble solid fraction after the enzymatic hydrolysis of cellulose was investigated for pretreated corn stover under a variety of recycling conditions. Results It was found that a significant amount of cellulase activity could be recovered by recycling the insoluble biomass fraction, and the enzyme dosage could be decreased by 30% to achieve the same glucose yields under the most favorable conditions. Enzyme productivity (g glucose produced/g enzyme applied) increased between 30 and 50% by the recycling, depending on the reaction conditions. While increasing the amount of solids recycled increased process performance, the methods applicability was limited by its positive correlation with increasing total solids concentrations, reaction volumes, and lignin content of the insoluble residue. However, increasing amounts of lignin rich residue during the recycle did not negatively impact glucose yields. Conclusions To take advantage of this effect, the amount of solids recycled should be maximized, based on a given processes ability to deal with higher solids concentrations and volumes. Recycling of enzymes by recycling the insoluble solids fraction was thus shown to be an effective method to decrease enzyme usage, and research should be continued for its industrial application.
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