Preface

When I was invited by InTech Open Access Publisher to edit a book on polysaccharides, I accepted the challenge since to me polysaccharides constitute a wide variety of biological polymers with diverse composition, physical characteristics and biological activity and have been the focus of my research career. These naturally occurring entities have been studied for their chemical and physical properties and more recently for bioactivity. They have been used in the food industry for functions such as thickeners and protective coatings. Industrial uses of polysaccharides in cosmetics, textiles and medicines are based on rheological, emulsifying and stabilizing properties of polysaccharides. Even though carbohydrates have a long history of chemical and physical study, properties of polysaccharides with relation to structure activity/function has not been an area of in depth study. Polysaccharides of bacterial origin however gained interest in the 1980's due to their potential as vaccine formulations. Therefore the detailed chemical structures of capsular polysaccharides, LPS and exopolysaccharides were elucidated leading to discovery of new naturally occurring sugars. The plant derived polysaccharides such as the hemicelluloses and starch and other specific polysaccharides such as inulin, beta glucans, alginates and pectins are very well documented and have been studied over a longer period of time.

Other than the chemical and physical properties of the polysaccharides, the genetic involvements of the biosynthetic processes which imparts specificity to the structure and thereby its action, have also warranted much study leading to a better understanding of the structure activity relationship. Thus the areas of study of polysaccharides cover several disciplines. In compiling this book, the contributions on polysaccharides from diverse sources such as animals, plants and microorganisms were received and sectioned according to their properties and applications.

The first section deals with sources of polysaccharides and their biological properties. A wide range of polysaccharides from bacterial origin to plants and lichens are presented along with their biological applications. The many applications of chitosan, the most abundant polysaccharide of animal origin, in areas from food, medicine, agriculture, pharmacy and other industries is revisited in the first chapter. The second chapter focusses on glucan polysaccharides, abundantly produced by microorganisms, having properties valuable in food uses. Here the yeast cell wall derived glucans and their products with applications in the food and health industries are presented. Biosynthesis of Bacterial polysaccharides occurs through elaborate mechanisms. The biosynthetic mechanisms leading to various structural changes in the O-antigens of bacterial polysaccharides are discussed in chapter 3. Variations in structure of the polysaccharides are shown to affect the biological properties and hence pathogenicity. Chapter 4 considers the genetic control of the biosynthesis of exopolysacchrides of Rhizobium leguminosarum. It is shown that diversity of the exopolysaccharides biosynthesized results from genetic rearrangements of the glycosyl transferase genes and other genes involved in translocation of the repeating units. The next chapter is devoted to the study of virulence and pathogenesis due to the capsular polysaccharides of *Burkholderia pseudomallei* . Several studies have been performed on bacterial polysaccharides as candidates for vaccines and it has been shown that virulence is due to changes in the capsular polysaccharide. Plant polysaccharides may be used for specific applications. However, the extraction of polysaccharides from plant waste products in timber industries with conversion of these polysaccharides into useful byproducts is a novel application. Chapter 6 addresses this showing that biomass obtained from large scale processing of Larch wood can be converted into valuable materials with many biological applications. The biological applications of the fructose rich levan polymer found abundantly in honey is discussed in the next chapter. The section ends with a lesser studied polysaccharide source: Lichens composed of a symbiotic relation between algae and fungi yielding polysaccharides which have been investigated for biological significance indicating antitumour, immunomodulatry and anti-inflammatory activities.

Chemical and physical characterizations are important aspects when dealing with understanding the uses of polysaccharides in relation to their properties. The second section discusses methods required for characterization and estimation of spatial arrangement and results obtained therefrom. The five chapters in this section deal with physical properties, methods of characterization and chemical analysis techniques useful for structure determination of a range of polysaccharides from the animal world (chitosan) to polysaccharides from microbes (diatoms). The structural dynamics of chitosan, its conformation and its interactions with biological materials starts off this section. The importance of conformation and molecular modelling is known with drug design studies. Likewise the structural dynamics of polysaccharides are useful for identifying interactions between polysaccharides and biological entities as well as nanoparticles. The use of Quantum chemical methods to explain the template synthesis of proteoglycans is described in the next chapter. Chapter 11 in this section deals with some methods which are essential for elucidating the structure of a polysaccharide. The focus is on the use of mass spectral analysis for determining structures at very low concentration. Other than the basic techniques for chemical characterization, the application of physico-chemical techniques such as laser light scattering and atomic force microscopy is described in the characterization of diatom polysaccharides. The final chapter on biofilm matrices deals with problems encountered in isolation of the biofilm polysaccharides and reviews the chemical and physical methods available.

The remaining two sections comprise applications of polysaccharides in the food industry and applications in the pharmaceutical industry. Various studies on polysaccharides as carriers of drugs, film formers in food protection applications exhibit the versatility of polysaccharides in many areas beneficial for human health. Section 3 deals with applications of polysaccharides in the food industry. Food consists of many components with proteins, fat and polysaccharides being the macro constituents. The composition and the interaction among the food components are important determinants for stability and organoleptic properties of the food item. The importance of polysaccharide-protein interaction and their relevance in food colloids is presented as a factor in emulsion stability determination in chapter 14. In the next chapter, the advantages of antibacterial and antioxidant activities of chitosan in bioactive coatings used for marine based foods, as well as exploiting the physical properties for gelling action and encapsulation are discussed. A whole gamut of functions of polysaccharides in films and coatings as carriers and protectors of bioactive additives and their role in improving food quality follows in chapter 16. Dietary fibre in food imparts health benefits. The polysaccharides cellulose and hemicelluloses are recognized as dietary fibres. The importance of dietary fibres for availability of nutrients is presented in the next chapter. The section ends with the advantages of starch as a source of energy. Modification of the properties of starch through biotechnological manipulation and production of high amylose starches is reviewed in this chapter.

X Preface

Biosynthesis of Bacterial polysaccharides occurs through elaborate mechanisms. The biosynthetic mechanisms leading to various structural changes in the O-antigens of bacterial polysaccharides are discussed in chapter 3. Variations in structure of the polysaccharides are shown to affect the biological properties and hence pathogenicity. Chapter 4 considers the genetic control of the biosynthesis of exopolysacchrides of Rhizobium leguminosarum. It is shown that diversity of the exopolysaccharides biosynthesized results from genetic rearrangements of the glycosyl transferase genes and other genes involved in translocation of the repeating units. The next chapter is devoted to the study of virulence and pathogenesis due to the capsular polysaccharides of *Burkholderia pseudomallei* . Several studies have been performed on bacterial polysaccharides as candidates for vaccines and it has been shown that virulence is due to changes in the capsular polysaccharide. Plant polysaccharides may be used for specific applications. However, the extraction of polysaccharides from plant waste products in timber industries with conversion of these polysaccharides into useful byproducts is a novel application. Chapter 6 addresses this showing that biomass obtained from large scale processing of Larch wood can be converted into valuable materials with many biological applications. The biological applications of the fructose rich levan polymer found abundantly in honey is discussed in the next chapter. The section ends with a lesser studied polysaccharide source: Lichens composed of a symbiotic relation between algae and fungi yielding polysaccharides which have been investigated for biological significance indicating antitumour,

Chemical and physical characterizations are important aspects when dealing with understanding the uses of polysaccharides in relation to their properties. The second section discusses methods required for characterization and estimation of spatial arrangement and results obtained therefrom. The five chapters in this section deal with physical properties, methods of characterization and chemical analysis techniques useful for structure determination of a range of polysaccharides from the animal world (chitosan) to polysaccharides from microbes (diatoms). The structural dynamics of chitosan, its conformation and its interactions with biological materials starts off this section. The importance of conformation and molecular modelling is known with drug design studies. Likewise the structural dynamics of polysaccharides are useful for identifying interactions between polysaccharides and biological entities as well as nanoparticles. The use of Quantum chemical methods to explain the template synthesis of proteoglycans is described in the next chapter. Chapter 11 in this section deals with some methods which are essential for elucidating the structure of a polysaccharide. The focus is on the use of mass spectral analysis for determining structures at very low concentration. Other than the basic techniques for chemical characterization, the application of physico-chemical techniques such as laser light scattering and atomic force microscopy is described in the characterization of diatom polysaccharides. The final chapter on biofilm matrices deals with problems encountered in isolation of the biofilm polysaccharides and reviews the chemical and

immunomodulatry and anti-inflammatory activities.

physical methods available.

The final section of the book is devoted to pharmaceutical applications involving polysaccharides. The first two chapters deal with the use of polysaccharides as therapeutic agents. The well- known medicinal properties of ginseng with emphasis on the activity of its polysaccharides, followed by the interaction of polysaccharides from red sea weed with virus, starts off this section. The next three chapters are devoted to the use of polysaccharides as carriers of drugs. The first of these, (chapter 21) deals with the use of beta glucans as drug delivery vehicles. Drug delivery vehicles using synthetic polymers as well as natural polymers have been in circulation for some time. With the advances in nanotechnology, nanoparticle use for drug delivery has taken the centre stage. This chapter looks into formation of glucan nanoparticles to enhance the property of the drug delivery vehicle. Chapter 22 on the other hand presents the formation of supramolecular complexes for efficient delivery of poorly water soluble drugs. On a different note, the effect of dietary fibre on availability of drugs with chitosan as the dietary fibre is evaluated in the next chapter. In conclusion, the long standing debate on the use of polysaccharides as vaccines and the future direction of carbohydrates as successful candidates is argued.

As evident from the diversity of the applications of polysaccharides presented in this book, study of carbohydrates brings us to a rare world where the abundance of sources and variety of structures is both mind boggling and intriguing. Carbohydrates have been explored since the beginning of chemical investigations and polysaccharides will continue to exert its sweet essence on researchers dabbling in the

#### XVI Preface

chemistry, physics and biology of this ubiquitous biopolymer. There is still a wealth of knowledge to be explored in the study of polysaccharides.

I wish to acknowledge with thanks, the assistance provided by the publishing team at InTech and their courteous service and prompt responses that made this a pleasant task. To the contributors who provided valuable insight into various aspects of polysaccharides, a big thank you. I wish them success in their future endeavours on polysaccharide research. Last but not least, the support and encouragement provided by my husband and family during this assignment which sustained me throughout the project is valued highly.

#### **Professor Desiree Nedra Karunaratne**

Department of Chemistry, University of Peradeniya, Peradeniya, Sri Lanka **Sources and Biological Properties of Polysaccharides** 
