Fundamental Studies on the Enzymatic Liquefaction and Rheology of Cellulosic Biomass Via Magnetic Resonance Imaging Velocimetry PDF Download
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Author: Maria Jose Cardona
Publisher:
ISBN: 9781339542188
Category :
Languages : en
Pages :
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Book Description
Worldwide need for alternatives to fossil fuels has driven significant research effort toward the development and scale-up of sustainable forms of energy. Second-generation biofuels, obtained from the breakdown of lignocellulosic biomass (e.g., agricultural residues), present a promising alternative. In biofuel production, the enzymatic hydrolysis of cellulose to glucose is currently one of the most expensive steps in the biochemical breakdown of lignocellulosic biomass. Economic considerations for large-scale implementation of this process demand operation at high solids loadings of biomass (>15\% (w/w)) due to potential for higher product concentrations and reduction of water usage throughout the biorefining process. In the high-solids regime, however, biomass slurries form a high viscosity, non-Newtonian slurry that introduces processing challenges, especially during the initial stages of hydrolysis (liquefaction), due to the low availability of water in the bulk phase. Furthermore, a concomitant reduction in glucose yields with increase in solids loadings has been observed, a phenomenon that is not well understood, but if overcome could hold the key to achieving desirable yields during hydrolysis. In order to better understand liquefaction, a magnetic resonance imaging (MRI) rheometer was used to perform in-line, in situ, real-time, and noninvasive studies on biomass slurries undergoing enzymatic hydrolysis. Batch and fed-batch experiments were done on lignocellulosic and cellulosic substrates with both purified and mixtures of enzymes, under various reaction conditions. The mechanism of liquefaction was found to be decoupled from the mechanism of saccharification. In addition, end product inhibition was found to have an impact on both saccharification and liquefaction during the initial stage of hydrolysis, which has an impact on scale-up of hydrolysis processes. Lastly, to address and overcome high-solids limitations, a fed-batch liquefaction process based on using real-time slurry yield stress as a process control variable was designed and tested with a delignified cellulosic substrate. The timing of enzyme addition relative to biomass addition influenced process efficiency, and the upper limit of solids loading was ultimately limited by end product inhibition. The impact of these findings on process kinetic modeling and scale-up are also discussed.
Author: Maria Jose Cardona
Publisher:
ISBN: 9781339542188
Category :
Languages : en
Pages :
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Book Description
Worldwide need for alternatives to fossil fuels has driven significant research effort toward the development and scale-up of sustainable forms of energy. Second-generation biofuels, obtained from the breakdown of lignocellulosic biomass (e.g., agricultural residues), present a promising alternative. In biofuel production, the enzymatic hydrolysis of cellulose to glucose is currently one of the most expensive steps in the biochemical breakdown of lignocellulosic biomass. Economic considerations for large-scale implementation of this process demand operation at high solids loadings of biomass (>15\% (w/w)) due to potential for higher product concentrations and reduction of water usage throughout the biorefining process. In the high-solids regime, however, biomass slurries form a high viscosity, non-Newtonian slurry that introduces processing challenges, especially during the initial stages of hydrolysis (liquefaction), due to the low availability of water in the bulk phase. Furthermore, a concomitant reduction in glucose yields with increase in solids loadings has been observed, a phenomenon that is not well understood, but if overcome could hold the key to achieving desirable yields during hydrolysis. In order to better understand liquefaction, a magnetic resonance imaging (MRI) rheometer was used to perform in-line, in situ, real-time, and noninvasive studies on biomass slurries undergoing enzymatic hydrolysis. Batch and fed-batch experiments were done on lignocellulosic and cellulosic substrates with both purified and mixtures of enzymes, under various reaction conditions. The mechanism of liquefaction was found to be decoupled from the mechanism of saccharification. In addition, end product inhibition was found to have an impact on both saccharification and liquefaction during the initial stage of hydrolysis, which has an impact on scale-up of hydrolysis processes. Lastly, to address and overcome high-solids limitations, a fed-batch liquefaction process based on using real-time slurry yield stress as a process control variable was designed and tested with a delignified cellulosic substrate. The timing of enzyme addition relative to biomass addition influenced process efficiency, and the upper limit of solids loading was ultimately limited by end product inhibition. The impact of these findings on process kinetic modeling and scale-up are also discussed.
Author: David Michael Lavenson
Publisher:
ISBN: 9781267657190
Category :
Languages : en
Pages :
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Book Description
Enzymatic conversion of lignocellulosic substrates is an important step in the biorefining process for the production of fuels and chemicals. Industrial implementation of cellulosic ethanol processes has been hindered by the lack of an economic and efficient way of digesting the cellulosic biomass feedstock. In order to reduce unit operations costs in the areas of mixing, handling, pumping, and separations, mass solids contents of the feed biomass must exceed approximately 20%. Above approximately 10% solids concentrations, cellulosic suspensions behave as non-Newtonian slurries while most of the moisture is retained within the substrate walls, making mixing and homogenization challenging. The underlying transport phenomena that govern these suspensions are complex and not completely understood. In this work, mass transfer and rheological behavior of high solids cellulose substrates are investigated. These studies use magnetic resonance imaging (MRI) to measure: 1. diffusion and adsorption in cellulosic fiber beds using labeled paramagnetic tracers; 2. velocity flow profiles of suspensions in tube flow to obtain pertinent rheological parameters; and 3. effects of mixing on the rates of liquefaction and saccharification in highly concentrated cellulose suspensions. MRI is a non-invasive technique which has been used for flow-imaging, diffusion, and adsorption studies. It is highly advantageous for the opaque biomass system which cannot be examined using light microscopy or other optical methods. Other techniques are used to probe the effects of fiber properties on diffusion-adsorption, liquefaction, and saccharification. Diffusion coefficients for MnCl2 and Gd-BSA are reported for various cellulosic suspensions, including delignified cellulose and dilute-acid pretreated lignocellulosic biomass. Diffusion is found to be highly dependent on the rate of adsorption in the fiber beds. The adsorption behavior of BSA on various cellulosic substrates, both lignocellulosic and delignified, is also investigated. Biomass suspension yield stress values are measured using MRI, and the resolution and uncertainty of the MRI technique are compared quantitatively with literature data collected from conventional rheometers. The MRI technique compares well with conventional techniques and offers improvements in sampling size, sampling error, measurement time, and uncertainty. Lastly, rates of liquefaction and extent of saccharification are measured for high solids content fiber suspensions undergoing enzymatic hydrolysis. A significant difference in the rates of liquefaction and saccharification is attributed to initial homogenization of enzyme, indicating the benefits of mixing enzyme and substrate on the centimeter scale. Application of these results to future work and industrial implications is also discussed.
Author: Youngsoo Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 334
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Book Description
Author: Li Zhu
Publisher:
ISBN:
Category : Biomass energy
Languages : en
Pages :
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Book Description
Lignocellulose is a promising and valuable alternative energy source. Native lignocellulosic biomass has limited accessibility to cellulase enzyme due to structural features; therefore, pretreatment is an essential prerequisite to make biomass accessible and reactive by altering its structural features. The effects of substrate concentration, addition of cellobiase, enzyme loading, and structural features on biomass digestibility were explored. The addition of supplemental cellobiase to the enzyme complex greatly increased the initial rate and ultimate extent of biomass hydrolysis by converting the strong inhibitor, cellobiose, to glucose. A low substrate concentration (10 g/L) was employed to prevent end-product inhibition by cellobiose and glucose. The rate and extent of biomass hydrolysis significantly depend on enzyme loading and structural features resulting from pretreatment, thus the hydrolysis and pretreatment processes are intimately coupled because of structural features. Model lignocelluloses with various structural features were hydrolyzed with a variety of cellulase loadings for 1, 6, and 72 h. Glucan, xylan, and total sugar conversions at 1, 6, and 72 h were linearly proportional to the logarithm of cellulase loadings from approximately 10% to 90% conversion, indicating that the simplified HCH-1 model is valid for predicting lignocellulose digestibility. Carbohydrate conversions at a given time versus the natural logarithm of cellulase loadings were plotted to obtain the slopes and intercepts which were correlated to structural features (lignin content, acetyl content, cellulose crystallinity, and carbohydrate content) by both parametric and nonparametric regression models. The predictive ability of the models was evaluated by a variety of biomass (corn stover, bagasse, and rice straw) treated with lime, dilute acid, ammonia fiber explosion (AFEX), and aqueous ammonia. The measured slopes, intercepts, and carbohydrate conversions at 1, 6, and 72 h were compared to the values predicted by the parametric and nonparametric models. The smaller mean square error (MSE) in the parametric models indicates more satisfactorily predictive ability than the nonparametric models. The agreement between the measured and predicted values shows that lignin content, acetyl content, and cellulose crystallinity are key factors that determine biomass digestibility, and that biomass digestibility can be predicted over a wide range of cellulase loadings using the simplified HCH-1 model.
Author: Massachusetts Institute of Technology. Department of Nutrition and Food Science
Publisher:
ISBN:
Category :
Languages : en
Pages : 156
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 99
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Author: Nardrapee Karuna
Publisher:
ISBN: 9781369616132
Category :
Languages : en
Pages :
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Book Description
Lignocellulosic biomass is the most promising feedstock for renewable biofuel production. However, the inaccessibility of cellulose to cellulases limits saccharification rates of lignocellulosic biomass. To overcome this limitation, the bioconversion of lignocellulosic biomass typically employs thermochemical pretreatment to improve biomass digestibility. Yet, the mechanisms of how pretreatment improves the cellulose saccharification reaction are still unresolved. I hypothesized that quantification of the change in “the accessibility of cellulose to cellulase” due to pretreatment can be used as an indicator to aid in predicting the impact of the pretreatment on downstream enzymatic saccharification rates of the biomass. Increasing the adsorption of cellulases to biomass alone, however, will not necessarily lead to higher saccharification rates if the enzymes are not productively bound. Cellulases bound productively to insoluble cellulose hydrolyze glycosidic bonds, while those that are non-productively bound do not. I had developed a direct method to measure productive and non-productive binding of the cellobiohydrolase Cel7A from Trichoderma reesei (TrCel7A) on cellulose as a means to quantify the accessibility of cellulose to cellulases. Since productive cellulase binding to cellulose results in hydrolysis and can be quantified by measuring hydrolysis rates. Of the five cellulosic substrates from different sources and processing histories examined in this study, swollen filter paper and bacterial cellulose had higher productive binding capacities of ~ 6 [mu]mol/g while filter paper, microcrystalline cellulose, and algal cellulose had lower productive binding capacities of ~ 3 [mu]mol/g. There was no difference in the affinity of TrCel7A to the productive binding sites on the cellulosic substrates. The productive binding capacity of the cellulosic substrates, however, did not correlate with extent time saccharification yields. I further applied the method to quantify the initial productive binding capacity of cellulose in biomass to cellulases. Productive binding capacities of five different types of biomass: untreated rice straw, washed-alkaline pretreated rice straw, acidified-alkaline pretreated rice straw, untreated tomato pomace, and ionic-liquid pretreated tomato pomace, were demonstrated. Pretreatment improved the digestibility of the biomass and increased the productive binding capacities. The were no significant differences in the productive binding capacities of alkaline pretreatment on rice straw due to different post-pretreatment processes. However, washing-process after alkaline pretreatment increased the affinity of TrCel7A to biomass than untreated rice straw and acidified pretreated rice straw by 2-fold. Though, the differences of the affinity of TrCel7A of untreated and ionic-liquid pretreated tomato pomace were not observed. In addition, there was a positive correlation between productive binding capacity and a long term saccharification extent. It implied that the initial productive binding capacity in biomass was a rate-limiting factor of enzymatic hydrolysis of cellulose in biomass. Thus, higher initial productive binding capacity suggested higher yield of extent of hydrolysis could be achieved.The assessment of productive binding capacity of cellulose to cellulase by using cellulase as a direct probe revealed “a biochemical accessibility,” or the number of binding sites, of cellulosic biomass to cellulases. To investigate “a physical accessibility” of cellulosic biomass to cellulase enzyme, two-dimensional proton nuclear magnetic resonance (2D - 1H NMR) relaxometry: T[subscript 1]-T[subscript 2] correlation was applied as a tool by using water as a probe. The water in samples – glass frit filters, filter paper, swollen cellulose, untreated and SO2-steam pretreated spruce, untreated and alkaline pretreated rice straw and untreated and ionic-liquid pretreated tomato pomace – were determined. Moreover, the accessibility of biomass to cellulase by using bovine serum albumin (BSA) as a cellulase proxy to avoid a change of samples due to hydrolysis reaction were observed. The accessible area for BSA tend to have higher osmotic pressure that drawn neighboring water in to the area, including water from BSA inaccessible area. As a result, increasing mobility of water in the BSA accessible areas and disappearing of some compartments were observed, when comparing with sample in pure water. In addition, water in hydrolyzed biomass were investigated. This was an indirect investigation of the accessibility of cellulose to cellulase because the changes of a compartment after hydrolysis were a result from hydrolysis reaction. Although there was still inconclusive of the correlation among the saccharification extent, initial productive binding capacity of cellulose and the exiting of water in biomass, a potential to use the initial productive binding capacity of cellulose and water in biomass as indicators in predicting saccharification extent of biomass was further discussed.
Author: Wayne B. Severn
Publisher:
ISBN:
Category : Biomass chemicals
Languages : en
Pages : 254
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Book Description
Author: Philippe Coussot
Publisher: John Wiley & Sons
ISBN: 0471720569
Category : Technology & Engineering
Languages : en
Pages : 311
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Book Description
A comprehensive examination of rheometry theory and its practical applications This publication enables readers to understand and characterize the flow properties of complex fluids and, with this knowledge, develop a wide range of industrial and consumer products. The author fills a gap in the current literature by presenting a comprehensive description of the rheological behavior of pastes, suspensions, and granular materials and by offering readers the rheometrical techniques needed to effectively characterize these materials. With his extensive experience in both academic and industrial research, the author is able to take the field to a new level in: * General schematic classification of the behavior of pastes,suspensions, and granular materials * Systematic review, analysis, and quantification of experimental problems with complex fluids * Insight into the flow behavior of complex fluids gained through the most recent discoveries and research techniques * Comprehensive rheometrical analysis of data obtained from research across a broad range of industries In addition to gaining a thorough understanding of the theory underlining rheometry, readers discover its many practical applications. Throughout the publication, specific examples are provided that illustrate how theory is applied, including examples involving food, civil engineering, cosmetics, pharmaceuticals, paper coatings, paint and ink, ceramics, sewage sludges, granular materials, and natural materials. In summary, this publication provides a comprehensive review of the behavior of pastes, suspensions, and granular materials as well as detailed analysis of rheometrical techniques. Everything needed to determine the behavior and movement of complex fluids is provided. It is, therefore, a recommended resource for rheologists, engineers, and researchers, as well as students who deal with complex fluids in product formulation, quality and process control, and process plant design.
Author: J.F. Sadoc
Publisher: Springer Science & Business Media
ISBN: 9401591571
Category : Technology & Engineering
Languages : en
Pages : 611
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Book Description
A general and introductory survey of foams, emulsions and cellular materials. Foams and emulsions are illustrations of some fundamental concepts in statistical thermodynamics, rheology, elasticity and the physics and chemistry of divided media and interfaces. They also give rise to some of the most beautiful geometrical shapes and tilings, ordered or disordered. The chapters are grouped into sections having fairly loose boundaries. Each chapter is intelligible alone, but cross referencing means that the few concepts that may not be familiar to the reader can be found in other chapters in the book. Audience: Research students, researchers and teachers in physics, physical chemistry, materials science, mechanical engineering and geometry.
