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: Anuj Chandel
Publisher: BoD – Books on Demand
ISBN: 9535111191
Category : Technology & Engineering
Languages : en
Pages : 288
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Book Description
This book provides important aspects of sustainable degradation of lignocellulosic biomass which has a pivotal role for the economic production of several value-added products and biofuels with safe environment. Different pretreatment techniques and enzymatic hydrolysis process along with the characterization of cell wall components have been discussed broadly. The following features of this book attribute its distinctiveness: This book comprehensively covers the improvement in methodologies for the biomass pretreatment, hemicellulose and cellulose breakdown into fermentable sugars, the analytical methods for biomass characterization, and bioconversion of cellulosics into biofuels. In addition, mechanistic analysis of biomass pretreatment and enzymatic hydrolysis have been discussed in details, highlighting key factors influencing these processes at industrial scale.
Author: Deepak K. Tuli
Publisher: Elsevier
ISBN: 0128218967
Category : Technology & Engineering
Languages : en
Pages : 416
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Book Description
Current Status and Future Scope of Microbial Cellulases not only explores the present and future of cellulase production, it also compares solid state fermentation (SSF) and submerged fermentation (SMF) for cellulase production. Chapters explore bioprocess engineering, metabolic engineering and genetic engineering approaches for enhanced cellulase production, including the application of cellulase for biofuel production. This important resource presents current technical status and the future direction of advances in cellulase production, including application of cellulases in different sectors. - Covers the present industrial scenarios and future prospect of cellulase production - Describes the molecular structure of cellulase - Explores genetic engineering, metabolic engineering and other approaches for improved cellulase production - Includes different applications of cellulases, including their application in the bioenergy sector
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: Vincenza Faraco
Publisher: Springer Science & Business Media
ISBN: 3642378617
Category : Science
Languages : en
Pages : 207
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Book Description
Bioethanol has been recognized as a potential alternative to petroleum-derived transportation fuels. Even if cellulosic biomass is less expensive than corn and sugarcane, the higher costs for its conversion make the near-term price of cellulosic ethanol higher than that of corn ethanol and even more than that of sugarcane ethanol. Conventional process for bioethanol production from lignocellulose includes a chemical/physical pre-treatment of lignocellulose for lignin removal, mostly based on auto hydrolysis and acid hydrolysis, followed by saccharification of the free accessible cellulose portions of the biomass. The highest yields of fermentable sugars from cellulose portion are achieved by means of enzymatic hydrolysis, currently carried out using a mix of cellulases from the fungus Trichoderma reesei. Reduction of (hemi)cellulases production costs is strongly required to increase competitiveness of second generation bioethanol production. The final step is the fermentation of sugars obtained from saccharification, typically performed by the yeast Saccharomyces cerevisiae. The current process is optimized for 6-carbon sugars fermentation, since most of yeasts cannot ferment 5-carbon sugars. Thus, research is aimed at exploring new engineered yeasts abilities to co-ferment 5- and 6-carbon sugars. Among the main routes to advance cellulosic ethanol, consolidate bio-processing, namely direct conversion of biomass into ethanol by a genetically modified microbes, holds tremendous potential to reduce ethanol production costs. Finally, the use of all the components of lignocellulose to produce a large spectra of biobased products is another challenge for further improving competitiveness of second generation bioethanol production, developing a biorefinery.
Author: G.T. Tsao
Publisher: Springer
ISBN: 3540491945
Category : Science
Languages : en
Pages : 297
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Book Description
This volume describes recent advances in the bioconversion of lignocellulosics. It starts with two articles on genetics and properties of cellulases and their re- tion kinetics and mechanisms. The cost of cellulases has been a hindrance to large scale use of enzymatic hydrolysis. Two articles on cellulase production by submerged fermentation and by solid state fementation are included to describe the state of the art in this area. Dilute acid hydrolysis of cellulose continues to be of interest as well as potentially useful. The most recent advances in this area is also covered. A great deal of progress has been made in genetic engineering for improved regulation of xylose fermentation by yeasts. An article on genetically engineered Saccharomyces for simulteaneous fermentation of glucose and xylose describes the importance advances made in production of fuel ethanol from lignocellulosic biomass. In recent years, there has been increasing interests in recycling and the reuse of scrap paper as well as environment considerations. A contribution is presented which describes the research perspectives in that area. Finally, recent advances in the use of lignocellulosic biomass for the p- duction of ethanol and organic acids are presented in two articles. Renewable resources are inevitably of great importance in the years to come. There is a never-ending search for better living conditions for human beings. The more resource materials can be recycled, the richer we will be.
Author: S.I. Mussatto
Publisher: Elsevier
ISBN: 0128025611
Category : Technology & Engineering
Languages : en
Pages : 676
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Book Description
Biomass Fractionation Technologies for a Lignocellulosic Feedstock-based Biorefinery reviews the extensive research and tremendous scientific and technological developments that have occurred in the area of biorefinering, including industrial processes and product development using ‘green technologies’, often referred as white biotechnology. As there is a huge need for new design concepts for modern biorefineries as an alternative and amendment to industrial crude oil and gas refineries, this book presents the most important topics related to biomass fractionation, including advances, challenges, and perspectives, all with references to current literature for further study. Presented in 26 chapters by international field specialists, each chapter consists of review text that comprises the most recent advances, challenges, and perspectives for each fractionation technique. The book is an indispensable reference for all professionals, students, and workers involved in biomass biorefinery, assisting them in establishing efficient and economically viable process technologies for biomass fractionation. Provides information on the most advanced and innovative pretreatment processes and technologies for biomass Reviews numerous valuable products from lignocellulose Discusses integration of processes for complete biomass conversion with minimum waste generation Identifies the research gaps in scale-up Presents an indispensable reference for all professionals, students, and workers involved in biomass biorefinery, assisting them in establishing efficient and economically viable process technologies for biomass fractionation
Author: Anuj Kumar Chandel
Publisher: John Wiley & Sons
ISBN: 1119735955
Category : Science
Languages : en
Pages : 436
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Book Description
Lignocellulose Bioconversion Through White Biotechnology Comprehensive resource summarizing the recent technological advancements in white biotechnology and biomass conversion into fuels, chemicals, food, and more Lignocellulose Bioconversion Through White Biotechnology presents cutting-edge information on lignocellulose biomass conversion, detailing how white biotechnology can develop sustainable biomass pretreatment methods, effective plant cell wall degrading enzymes to yield high quality cellulosic sugars, and the eventual conversion of these sugars into fuels, chemicals, and other materials. To provide comprehensive coverage of the subject, the work offers in-depth critical analysis into both techno-economic and life cycle analysis of lignocellulose-based products. Each of the 16 chapters, written by a well-qualified and established researchers, academics, or engineers, presents key information on a specific facet of lignocellulose-based products. Topics covered include: Lignocellulose feedstock availability, types of feedstock, and potential crops that are of high interest to the industry Lignocellulose bioconversion, including both foundational technical aspects and new modern developments Plant cell wall degrading enzymes, including cellulase improvement and production challenges/solutions when scaling up Improvements and challenges when considering fermenting microorganisms for cellulosic sugars utilization Scaling up of lignocellulose conversion, including insight into current challenges and future practices Techno-economic aspects of lignocellulose feedstock conversion, green consumerism and industrialization aspects of renewable fuels/chemicals Students, academics, researchers, bio-business analysts, and policy-makers working on sustainable fuels, chemicals, materials, and renewable fuels can use Lignocellulose Bioconversion Through White Biotechnology to gain invaluable expert insight into the subject, its current state of the art, and potential exciting future avenues to explore.
Author: Manish Srivastava
Publisher: Springer
ISBN: 3030147266
Category : Science
Languages : en
Pages : 218
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Book Description
Cellulase is a key enzyme of industrial interest and plays a crucial role in the hydrolysis of cellulose, a prime component of plant cell walls. Cellulase covers a broad area in the global market of industrially important enzymes and it is considered as the third largest industrial enzyme globally. Additionally, cellulase contributes about 20% of the total enzyme market globally because of its massive demand in various industries such as in biofuel production, pulp, paper, textile, food, and beverages, as well as in detergent industries. Among these, the demand of cellulase may become frequently selected in the commercial production of biofuels in the future and thus will further increase demand of cellulase in the biofuel industry. Because biofuel production is still not realized in a cost-effective, practical implementation due to its high cost (the higher cost of biofuels is due to higher production costs of enzymes), there is a need to introduce these types of approaches, which will help to lower the cost of enzyme production for developing overall economic biofuel production.
Author: Wilfred Vermerris
Publisher: Springer Science & Business Media
ISBN: 0387708057
Category : Technology & Engineering
Languages : en
Pages : 464
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Book Description
Ethanol as an alternative fuel is receiving a lot of attention because it addresses concerns related to dwindling oil supplies, energy independence, and climate change. The majority of the ethanol in the US is produced from corn starch. With the US Department of Energy’s target that 30% of the fuel in the US is produced from renewable resources by 2030, the anticipated demand for corn starch will quickly exceed the current production of corn. This, plus the concern that less grain will become available for food and feed purposes, necessitates the use of other feedstocks for the production of ethanol. For the very same reasons, there is increasing research activity and growing interest in many other biomass crops. Genetic Improvement of Bio-Energy Crops focuses on the production of ethanol from lignocellulosic biomass, which includes corn stover, biomass from dedicated annual and perennial energy crops, and trees as well as a number of important biomass crops. The biomass is typically pretreated through thermochemical processing to make it more amenable to hydrolysis with cellulolytic enzymes. The enzymatic hydrolysis yields monomeric sugars that can be fermented to ethanol by micro-organisms. While much emphasis has been placed on the optimization of thermo-chemical pretreatment processes, production of more efficient hydrolytic enzymes, and the development of robust microbial strains, relatively little effort has been dedicated to the improvement of the biomass itself.
