Download or read book Fundamental Study of Structural Features Affecting Enzymatic Hydrolysis of Lignocellulosic Biomass written by Li Zhu and published by . This book was released on 2005 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fundamental Factors Affecting Enzymatic Hydrolysis of Lignocellulosic Biomass written by Zhiying Yu and published by . This book was released on 2013 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterization and Saccharification of Ionic Liquid Pretreated Lignocellulosic Biomass written by Indira Priya Samayam and published by . This book was released on 2011 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this dissertation research is to gain a more fundamental understanding of the impact of ionic liquid (IL) pretreatment of lignocellulosic biomass in production of ethanol and other chemicals through a sugar platform and biochemical conversion of polysaccharides to monomeric sugars. Recalcitrance of cellulose hydrolysis is a primary roadblock for efficient enzymatic conversion of lignocellulosic biomass to monomeric sugars that are fermented to ethanol or other products. The structure of lignocellulosic biomass is rendered amenable to enzymatic saccharification upon IL pretreatment. Changes in the structure of cellulose in relation to the biomass digestibility with varying ionic liquid (IL) pretreatment were examined. Conversion of native cellulose I to amorphous cellulose or cellulose II improved the susceptibility of cellulose to enzymatic hydrolysis. The performance of commercial enzyme mixtures were evaluated through saccharification of IL pretreated biomass substrates (poplar and switchgrass) at low biomass slurry concentrations. Poplar and switchgrass hydrolysis with commercial cellulase, Spezyme CP, and Multifect Xylanase showed synergism between the two enzymes. However, switchgrass hydrolysis was less complete than that of poplar, likely due to differences in hemicellulose structural features. Hydrolysis of polysaccharides in lignocellulose at high biomass slurry concentrations is essential in economical fermentation of hydrolyzates to ethanol and other products. Commercial enzyme mixtures were varied for simultaneous or sequential hydrolysis and fermentation of pentose and hexose sugars with Pichia stipitis for IL treated poplar. In sequential hydrolysis of poplar at modest enzyme loadings of 9 mg/g xylan Multifect Xylanase, 1.8 mg/ g xylan SXA (ß-xylosidase) at 50°C in the first step and 10 FPU/g glucan Spezyme CP, and 40 CBU/g glucan Novozyme 188 at 25°C in the second step, the yields of glucose and xylose at 15% (w/v) solid loadings were 61% and 83%, respectively. The incomplete hydrolysis may be due to the accumulation of cellobiose and low activity of enzymes at 25°C. Further increase in Novozyme 188 loadings or hydrolysis may improve hydrolysis yields. A maximum of 66% theoretical ethanol yield based on initial sugar analysis of poplar was expected from these hydrolyzates if all the released sugars were fermented to ethanol. In sequential hydrolysis and fermentation with P. stipitis, 56% theoretical ethanol yields based on the initial sugar composition of poplar respectively was achieved.
Download or read book Biomass Fractionation Technologies for a Lignocellulosic Feedstock Based Biorefinery written by S.I. Mussatto and published by Elsevier. This book was released on 2016-02-18 with total page 676 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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
Download or read book Advances in Bioprocess Technology written by Pogaku Ravindra and published by Springer. This book was released on 2015-08-13 with total page 529 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an extensive overview of the latest research in environmentally benign integrated bioprocess technology. The cutting edge bioprocess technologies highlighted in the book include bioenergy from lignocellulose materials, biomass gasification, ethanol, butanol, biodiesel from agro waste, enzymatic bioprocess technology, food fermentation with starter cultures, and intellectual property rights for bioprocesses. This book further addresses niche technologies in bioprocesses that broadens readers’ understanding of downstream processing for bio products and membrane technology for bioprocesses. The latest developments in biomass and bioenergy technology are reviewed exhaustively, including IPR rights, nanotechnology for bioenergy products, biomass gasification, and biomass combustion. This is an ideal book for scientists, engineers, students, as well as members of industry and policy-makers. This book also: Addresses cutting-edge technologies in bioprocesses Broadens readers’ understanding of metabolic engineering, downstream processing for bioproducts, and membrane technology for bioprocesses Reviews exhaustively the latest developments in biomass and bioenergy technology, including nanotechnology for bioenergy products, biomass gasification, biomass combustion, and more
Download or read book Biomass Recalcitrance written by Michael Himmel and published by Wiley-Blackwell. This book was released on 2008-06-23 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book examines the connection between biomass structure, ultrastructure, and composition, to resistance to enzymatic deconstruction, with the aim of discovering new cost-effective technologies for biorefineries. It contains chapters on topics extending from the highest levels of biorefinery design and biomass life-cycle analysis, to detailed aspects of plant cell wall structure, chemical treatments, enzymatic hydrolysis, and product fermentation options."--Pub. desc.
Download or read book Pretreatment Techniques for Biofuels and Biorefineries written by Zhen Fang and published by Springer Science & Business Media. This book was released on 2013-01-04 with total page 461 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book includes 19 chapters contributed by the world's leading experts on pretreatment methods for biomass. It extensively covers the different types of biomass (e.g. molasses, sugar beet pulp, cheese whey, sugarcane residues, palm waste, vegetable oil, straws, stalks and wood), various pretreatment approaches (e.g. physical, thermal, chemical, physicochemical and biological) and methods that show the subsequent production of biofuels and chemicals such as sugars, ethanol, extracellular polysaccharides, biodiesel, gas and oil. In addition to traditional methods such as steam, hot-water, hydrothermal, diluted-acid, organosolv, ozonolysis, sulfite, milling, fungal and bacterial, microwave, ultrasonic, plasma, torrefaction, pelletization, gasification (including biogas) and liquefaction pretreatments, it also introduces and discusses novel techniques such as nano and solid catalysts, organic electrolyte solutions and ionic liquids. This book offers a review of state-of-the-art research and provides guidance for the future paths of developing pretreatment techniques of biomass for biofuels, especially in the fields of biotechnology, microbiology, chemistry, materials science and engineering. It intends to provide a systematic introduction of pretreatment techniques. It is an accessible reference work for students, researchers, academicians and industrialists in biorefineries. Zhen Fang is a Professor of Bioenergy and the leader and founder of the biomass group at the Xishuangbanna Tropical Botanical Garden of the Chinese Academy of Sciences. He is also an adjunct full Professor of Life Sciences at the University of Science and Technology of China.
Download or read book Lignocellulose written by Kelly L. Pittman and published by . This book was released on 2015 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is focused on new developments in lignocellulose research. In particular, lignocellulosic biomass has been the focus of considerable attention for the production of a wide range of valuable products in biorefineries which aim to utilize renewable starting material instead of fossil based products. The authors focus on the usage of hemicellulose to produce various bio-based products including platform chemicals that have considerable market potential in the coming years. Other chapters in the book review studies which have explored how the lignocellulose morphological structure affects the enzymatic hydrolysis reaction and the corresponding plant cell wall structural changes. Other chapters describe the state-of-the-art of pretreatment processes, fermentation processes, microbial lipid accumulation pathway and methanolysis of the microbial lipids to increase the yields of biodiesel as well as the challenges associated with the use of lignocellulosic biomass (LCB); the ways in which membrane technology has been gaining widespread recognition to substitute the existing separation and purification technologies, specifically, the applications of ionic liquid based membranes; and the quantitative composition of secretome of potent biomass hydrolyzing fungi along with their post translational modifications and also the role of PTMs.
Download or read book Lignocellulosic Biomass to Liquid Biofuels written by Abu Yousuf and published by Academic Press. This book was released on 2019-11-20 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lignocellulosic Biomass to Liquid Biofuels explores the existing technologies and most recent developments for the production of second generation liquid biofuels, providing an introduction to lignocellulosic biomass and the processes for its conversion into biofuels. The book demonstrates biorefinery concepts compared with petro refinery, as well as the challenges of second generation biofuels processing. In addition to current pre-treatment techniques and their technical, environmental and economic implications, chapters included also further examine the particularities of conversion processes for bioethanol, biobutanol and biodiesel through chemical, biochemical and combined approaches. Finally, the book looks into concepts and tools for techno-economic and environmental analysis, which include supply chain assessment, by-products, zero-waste techniques and process evaluation and optimization. Lignocellulosic Biomass to Liquid Biofuels is particularly useful for researchers in the field of liquid biofuels seeking alternative chemical and biochemical pathways or those interested advanced methods to calculate maximum yield for each process and methods to simulate the implications and costs of scaling up. Furthermore, with the introduction provided by this volume, researchers and graduate students entering the field will be able to quickly get up to speed and identify knowledge gaps in existing and upcoming technology the book's comprehensive overview. - Examines the state-of-the-art technology for liquid biofuels production from lignocellulosic biomass - Provides a comprehensive overview of the existing chemical and biochemical processes for second generation biofuel conversion - Presents tools for the techno-economic and environmental analysis of technologies, as well as for the scale-up simulation of conversion processes
Download or read book Thermochemical and Catalytic Conversion Technologies for Future Biorefineries written by Pradeep Verma and published by Springer Nature. This book was released on 2022-09-01 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book will attempt to provide an account of knowledge on biomass available for biomass-based biorefineries. Its focuses on understanding the recalcitrance of biomass and how it limits the overall conversion efficiency. It also gives an insight what are different conventional approaches available for pretreatment and hydrolysis of the biomass. The chapters deals with highlights how enzymes can be a powerhouse and play pioneering roles in biomass valorization. The book will also throw light on how technical aspects of thermochemical conversion strategies such as pyrolysis, gasification, organosolv methods for the generation of value-added materials such as high-quality bio-oil, biochars, and biobased chemicals. These high-value compounds can be put to widespread application in biofuel, biocatalyst, waste bioremediation (heavy metal removal), air purification and effluent treatment applications. The book will provide literature on the limitations of already existing technologies and provide prospects of each technology. This book is of interest to teachers, researchers, bioenergy scientists, capacity builders, and policymakers. Also, the book serves as additional reading material for undergraduate and graduate students of energy studies, chemical engineering, biotechnology, and environmental sciences. National and international energy scientists and policymakers will also find this to be a useful read.
Download or read book Developing a Fundamental Understanding of Biomass Structural Features Responsible for Enzymatic Digestibility written by Jonathan Patrick O'Dwyer and published by . This book was released on 2005 with total page 313 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lignocellulosic biomass is one of the most valuable alternative energy sources because it is renewable, widely available, and environmentally friendly. Unfortunately, enzymatic hydrolysis of biomass has been shown to be a limiting factor in the conversion of biomass to chemicals and fuels. This limitation is due to inherent structural features (i.e., acetyl content, lignin content, crystallinity, surface area, particle size, and pore volume) of biomass. These structural features are barriers that prevent complete hydrolysis; therefore, pretreatment techniques are necessary to render biomass highly digestible. The ability to predict the biomass reactivity based solely on its structural features would be of monumental importance. Unfortunately, no study to date can predict with certainty the digestibility of pretreated biomass. A concerted effort with Auburn University and Michigan State University has been undertaken to study hydrolysis mechanisms on a fundamental level. Predicting enzymatic hydrolysis based solely onstructural features (lignin content, acetyl content, and crystallinity index) would be a major breakthrough in understanding enzymatic digestibility. It was proposed to develop a fundamental understanding of the structural features that affect the enzymatic reactivity of biomass. The effects of acetyl content, crystallinity index (CrI), and lignin content on the digestibility of biomass (i.e., poplar wood, bagasse, corn stover, and rice straw) were explored. In this fundamental study, 147 poplar wood model samples with a broad spectrum of acetyl content, CrI, and lignin were subjected to enzymatic hydrolysis to determine digestibility. Correlations between acetyl, lignin, and CrI and linear hydrolysis profiles were developed with a neural network model in Matlab®. The average difference between experimentally measured and network-predicted data were +̲12%, +̲18%, and +̲27% for 1-, 6-, and 72-h total sugar conversions, respectively. The neural network models that included cellulose crystallinity as an independent variable performed better compared to networks with biomass crystallinity, thereby indicating that cellulose crystallinity is more effective at predicting enzymatic hydrolysis than biomass crystallinity. Additionally, including glucan slope in the 6-h and 72-h xylan slope networks and glucan intercept in the 6-h and 72-h xylan intercept networks improved their predictive ability, thereby suggesting glucan removal affects later-stage xylan digestibility.
Download or read book Cellulose Hydrolysis written by Liang-tseng Fan and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent economic trends, especially the worldwide decline in oil prices, and an altered political climate in the United States have combined to bring about major reductions in research on renewable energy resources. Yet there is no escaping the "facts of life" with regard to these resources. The days of inexpensive fossil energy are clearly numbered, the credibility of nuclear energy has fallen to a new low, and fusion energy stands decades or more from practical realization. Sooner than we may wish ,we will have to turn to renewable raw materials - plant "biomass" and, especially, wood - as significant suppliers of energy for both industry and everyday needs. It is therefore especially important to have a single, comprehensive and current source of information on a key step in any process for the technological exploitation of woody materials, cellulose hydrolysis. Further more, it is essential that any such treatment be unbiased with respect to the two methods - chemical and biochemical - for the breakdown of cellulose to sugars. Researchers on cellulose hydrolysis have frequently been chided by persons from industry, especially those individuals concerned with determining the economic feasibility of various technological alternatives. They tell us that schemes for the utilization of wood and other such resources fly in the face of economic realities.
Download or read book Pretreatment and Enzymatic Hydrolysis of Lignocellulosic Biomass written by Deisy Y. Corredor and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The performance of soybean hulls and forage sorghum as feed stocks for ethanol production was studied. The main goal of this research was to increase fermentable sugars' yield through high-efficiency pretreatment technology. Soybean hulls are a potential feedstock for production of bio-ethanol due to their high carbohydrate content ([approximately equals]50%) of nearly 37% cellulose. Soybean hulls could be the ideal feedstock for fuel ethanol production, because they are abundant and require no special harvesting and additional transportation costs as they are already in the plant. Dilute acid and modified steam-explosion were used as pretreatment technologies to increase fermentable sugars yields. Effects of reaction time, temperature, acid concentration and type of acid on hydrolysis of hemicellulose in soybean hulls and total sugar yields were studied. Optimum pretreatment parameters and enzymatic hydrolysis conditions for converting soybean hulls into fermentable sugars were identified. The combination of acid (H[subscript]2SO[subscript]4, 2% w/v) and steam (140 °C, 30 min) efficiently solubilized the hemicellulose, giving a pentose yield of 96%. Sorghum is a tropical grass grown primarily in semiarid and dry parts of the world, especially in areas too dry for corn. The production of sorghum results in about 30 million tons of byproducts mainly composed of cellulose, hemicellulose, and lignin. Forage sorghum such as brown midrib (BMR) sorghum for ethanol production has generated much interest since this trait is characterized genetically by lower lignin concentrations in the plant compared with conventional types. Three varieties of forage sorghum and one variety of regular sorghum were characterized and evaluated as feedstock for fermentable sugar production. Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and X-Ray diffraction were used to determine changes in structure and chemical composition of forage sorghum before and after pretreatment and enzymatic hydrolysis process. Up to 72% of hexose yield and 94% of pentose yield were obtained using "modified" steam explosion with 2% sulfuric acid at 140°C for 30 min and enzymatic hydrolysis with cellulase (15 FPU/g cellulose) and [Beta]-glucosidase (50 CBU/g cellulose).
Download or read book Lignocellulose Biorefinery Engineering written by Hongzhang Chen and published by Woodhead Publishing. This book was released on 2015-03-03 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: Biomass resources and their refining are key research topics internationally as alternatives to fossil fuel resources and oil refining. This book explores the heterogeneous nature of lignocellulosic biomass, which restricts its use as a raw material, and describes the theoretical basis of the lignocellulose refinery. It puts forward the theory of the integrated biomass refinery system, which produces multiple products, including biofuels, biomaterials, biochemicals, food and feed based on careful fractionation of the raw material. Chapter 1 introduces the significance and development of lignocellulose biorefining. Chapter 2 gives the theoretical basis of lignocellulose biorefinery engineering. Chapters 3 to 6 describe in detail biomass refinery engineering from the perspectives of feedstocks, conversions, products and processes respectively. Models of integrated industrial biomass refinery chains are presented in Chapter 7. Finally, Chapter 8 considers future trends in lignocellulose biorefining. - Explores mechanisms of selective fractionation of biomass based on biomass structural characteristics and product requirements - Addresses biological, physical and chemical conversion technologies, as well as combinations of different methods based on the biomass material characteristics - This thorough exploration of lignocellulose biorefining is written by an expert from a key research institute in this field
Download or read book Sustainable Degradation of Lignocellulosic Biomass written by Anuj Chandel and published by BoD – Books on Demand. This book was released on 2013-05-15 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Fundamental Studies on the Enzymatic Liquefaction and Rheology of Cellulosic Biomass Via Magnetic Resonance Imaging Velocimetry written by Maria Jose Cardona and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book The Impact Of Polysaccharides And Hydration On The Structure Of Cellulose written by Lin Fang and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The polysaccharide cellulose consists of [beta] linked D-glucose units, and is a major component of the cell wall of eukaryotic plants and algae. There are both amorphous and crystalline regions in the microfibrils. Cellulose crystal structure is determined by how chains are packed and interact through intramolecular and intermolecular hydrogen bonds and van der Waals interactions. Higher order microfibril assembly may occur through the process of co- crystallization, physical aggregation and bundling. The structure of native cellulose has important implications in the chemical or enzymatic transformation of cellulosic biomass, and for the development of new cellulose based composite materials.The cellulose chains at the surface of microfibrils are in intimate contact with hemicellulose and other small molecules including water, which will affect the crystallization process, and eventually impact degradability through chemical and enzymatic processes. A better understanding of those subjects has become the main focus of many researchers aiming to produce biofuels and other useful chemicals from lignocellulosic biomass. The development of a model system should permit more systematic exploration of the complex plant cell wall system. Bacterial cellulose (BC) synthesis in Gluconacetobacter can serve as a model system to study the basic principles that govern the biogenesis of cellulose as well as cellulose interaction with other polymers during synthesis. Synthesis of BC is a precisely and specifically regulated multi-step process, involving a large number of enzymes and complexes of catalytic and regulatory proteins. Generally, there are two immediate steps: formation of a glucan chain through the polymerization of glucose units and crystallization of the cellulose chain. The two steps are coupled and consecutive processes, and the rate of polymerization is determined by the rate of crystallization.In addition to cellulose, some other exopolysaccharides (EPS) have been isolated from the culture medium of cellulose-producing bacteria. Understanding the correlation between wateriiiiv soluble EPS and cellulose production is a goal of this study. Gluconacetobacter hansenii (G.hansenii) ATCC 53582 was found to produce different types of water soluble EPS. Those EPS have different levels of association to BC. At least a portion of the EPS can be released from the BC by 0.1M to 4M NaOH solution treatments. Hard to extract EPS (HE-EPS) released by 4M NaOH solutions have been characterized and contain approximately 75% mannose and 25% glucose. To study the effect of the EPS on BC synthesis, purified EPS were added to the medium at the start of cultivation and the BC produced was characterized. Results showed that the presence of HE-EPS in the culture medium interfered with the alignment of the BC crystals, but did not reduce crystal size. This is in contrast to similar studies performed using xyloglucan, xylan, and glucomannan. The width of the average ribbon increased by 60% when HE-EPS levels increased in the medium, which indicated that the HE-EPS could also modulate the bundling of cellulose ribbons. Based on the data, a mechanism for how HE-EPS alters cellulose formation and assembly was proposed. The addition of HE-EPS disturbs the preferential crystal orientation and increases the spacing of cellulose microfibrils without affecting crystallization by associating with ordered cellulose prior to physical aggregation or bundling. Those results may impact the interpretation of previous work, where BC is used as a pure model cellulose material.This study investigates the influence of carbon source on the cellulosic and non-cellulosic EPS produced by four Gluconacetobacter strains. The yields of bacterial cellulose and water- soluble polysaccharides were dependent on both carbon source and Gluconacetobacter strain. The carbon substrate also affected the composition of the free EPS. When galactose served as the exclusive carbon source, G.xylinus ATCC 53524 and ATCC 700178 produced a distinct alkaline stable crystalline product, which influenced the crystallization of cellulose. G. hansenii ATCC 23769 and ATCC 53582, however, did not exhibit any significant change in cellulose crystal properties when galactose was used as the carbon source. Microscopic observation furtherv confirmed significant incorporation of EPS into the cellulose composites. The cellulosic networkproduced from galactose medium showed distinctive morphological and structural features compared to that from glucose medium.Hydrolysis of lignocellulosic biomass is more complicated than that of pure cellulose due to the presence of lignin and hemicellulose. The properties of cellulose such as crystallinity, porosity, particle size, and the content and distribution of lignin and hemicellulose could all contribute to substrate digestibility. Therefore, the aim of this study is to use Gluconacetobacter as a model system to study how the interaction between cellulose and other polymers influence the enzymatic hydrolysis.Three different types of water-soluble polysaccharides produced from plants and G. xylinus were added to the fermentation medium. There are variations in the amounts of polysaccharides incorporated into the active G. xylinus system. Glucomannan demonstrated highest affinity to bacterial cellulose. According to morphological observations, the networks of hemicellulosic polysaccharides and bacterial cellulose appeared to coalesce more prominently compared to that of the bacterial cellulose produced in the presence of bacterial polysaccharides. The cellulase digestion studies were performed on bacterial cellulose with and without added polysaccharides, and an amorphous cellulose standard. The hydrolysis rate of the native bacterial cellulose increased drastically with the incorporation of certain types of mannose rich polysaccharides produced from plants and G. xylinus. Therefore, it seems reasonable to conclude that the altering physical aggregation and bundling of cellulose microfibrils with certain types of polysaccharides could improve the enzymatic hydrolysis efficiency without disrupting the crystal structure of cellulose significantly. This result could have implications for the genetic modification of plants for biofuel feedstocks.vi The change in the state of water in cellulose is important to its structural and mechanicalproperties. The goal of this component of the study is to investigate the hydration and dehydration induced structural changes of native cellulose. Never dried cotton, and never dried BC with and without added matrix polymer xyloglucan, are examined under the influence of dehydration and rehydration. Significant crystal structure changes were observed in the later stage of drying for both cotton and BC. The 1% lateral expansion in glucan chain spacing and 17% decrease of calculated Scherrer dimension were detected for cotton due to the distortion of the structure possibly caused by mechanical stresses associated with drying. No detectable changes on average glucan chain spacings were observed for large BC crystals. However, an average width decrease by 4.4 nm was discovered in the (010) direction, which was more significant than that observed in the (100) and (110) directions. It is hypothesized that co-crystallized elementary fibrils preferentially disassociate along the (010) plane resulting in a significant reduction of crystal width. In the BC-xyloglucan model composite, the presence of xyloglucan does not interfere with the dehydration behavior. Rehydration leads to some structural changes but to a lesser extent than the initial drying. High temperature dehydration induced deformation and crystal size changes are found to be non-reversible due to the removal of the last hydration layer on the cellulose surface.
