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INTRODUCTION
Pectin is a collective term to describe all the polysaccharides that contain D-galacturonic acid residues in their backbones (O’Neill et al., 1990). This group includes the methyl-esterified pectins, the de-esterified pectic acids and pectates (Goycoolea & Cárdenas, 2003). Pectin has been described in 1825 by the French chemist Henri Braconnot who identified this group of polysaccharides in many plant ut mainly focussed his studies on their gelling properties. These polysaccharides were named “pectic acid”, which is the direct translation of the Latin “coagulum” (Guillotin, 2005).
Pectins form a highly complex, heterogeneous group of acidic polysaccharides that have been isolated from the cell-walls of many higher plants and were found to be a major component of the cell-walls of dicotyledonous plants and gymnosperms (Goycoolea & Cárdenas, 2003; Ridley et al., 2001). These polymers are also abundant in the cell-walls of monocots (O’Neill et al., 1990). The pectic polysaccharides are the most abundant class of macromolecules within the primary cell-wall and are also located in the middle lamella, where they function in a number of growth and developmental processes (Mohnen, 1999). The highest concentration of pectin occurs in the middle lamella and cell corners with a gradual decrease from the primary cell-wall to the plasma membrane (Goycoolea & Cárdenas, 2003). Pectin concentration is greatly reduced or absent in the secondary cell-wall, which makes it the only major cell-wall polysaccharide that is restricted to the primary cell-wall (Willats et al., 2001b). These polysaccharides are also present in the junction zone between ells with secondary walls, including xylem and the fibre cells in woody tissue (Mohnen, 2008). These polysaccharides are especially abundant in the cell-walls of growing and dividing plant cells and are usually produced during the initial stages of cell growth (Goycoolea & Cárdenas, 2003; Mohnen, 2008).
Pectins greatly influence general properties of the cell-wall and play an important role in plant development, especially in the regulation of cell expansion and adhesion (Jarvis et al., 2003; Willats et al., 2001a). Many of the functionalities of pectins are related to their molecular mass and distribution, their D-galacturonic acid and neutral monosaccharide content and the distribution of their substituents (Yapo et al., 2007). These polysaccharides are of great importance to the food and cosmetic industries because of their natural gelling and stabilising properties (Gnanasambanda & Proctor, 1999; G llotin, 2005). Pectins are also considered to be important to the pharmaceutical industry, because of the positive effects on human health (Inngjerdingen et al., 2007). These polysaccharides are used in the production of many different speciality products, including edible and degradable films, adhesives, paper substitutes, foams and surface modifiers that are used in medical devices (Mohnen, 2008).
CHAPTER 1: STRUCTURE, BIOSYNTHESIS AND DEGRADATION OF PECTIN: A REVIEW
ABSTRACT
INTRODUCTION
STRUCTURE OF PECTIN
Structure of homogalacturonan
Structure of rhamnogalacturonan-I
Structure of rhamnogalacturonan-II
Structure of xylogalacturonan
INTERACTIONS AND LINKS OF THE PECTIC NETWORK
Macromolecular structure
Other cross-links
FUNCTION AND DISTRIBUTION OF THE PECTIC DOMAINS
Function and distribution of homogalacturonan
Function and distribution of rhamnogalacturonan-I
Function and distribution of rhamnogalacturonan-II
Function and distribution of xylogalacturonan
BIOSYNTHESIS OF PECTIN
Biosynthesis of homogalacturonan
Biosynthesis of xylogalacturonan
Biosynthesis of rhamnogalacturonan-I
Biosynthesis of rhamnogalacturonan-II
ENZYMATIC DEGRADATION OF PECTIN
Degradation of homogalacturonan
Degradation of rhamnogalacturonan-I
Degradation of rhamnogalacturonan-II
Degradation of xylogalacturonan
CONCLUSIONS
APPENDICES
REFERENCES
CHAPTER 2: PECTIC MONOSACCHARIDES AND TOTAL PECTIN CONTENT OF EUCALYPTUS WOOD
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
Sampling and preparation of wood samples
Hydrolysis and sample preparation
Analytical method
Experimental design and statistial analysis
RESULTS AND DISCUSSION
Separation of monosaccharides
Occurrence of pectic monosaccharides in wood
Total pectin content
CONCLUSIONS
APPENDICES
REFERENCES
CHAPTER 3: MONOSACCHARIDE COMPOSITION OF PECTIN FROM EUCALYPTUS WOOD
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
Monosaccharide composition of pectin
Experimental design and statistical analysis
RESULTS AND DISCUSSION
D-Galacturonic acid
L-Rhamnose
L-Arabinose
D-Galactose
CONCLUSIONS
APPENDICES
REFERENCES
CHAPTER 4: MACROMOLECULAR STRUCTURE OF THE PECTIN OF TWO EUCALYPTUS SPECI
INTRODUCTION
MATERIALS AND METHODS
Macromolecular composition of pectin
Experimental design and statistical analysi
RESULTS AND DISCUSSION
Molecular contribution of different domains to pectin
Pectic backbone
Macromolecular composition of rhamnogalacturonan-I
CONCLUSIONS
APPENDICES
REFERENCES
CHAPTER 5: PECTIN FROM EUCALYPTUS MACARTHURII
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
Sampling and preparation of wood samples
Analysis and determination of the content and composition of pectin
Experimental design and statistical analysis
Influence of wood tissue type and tree age class
Influence of tree species
CONCLUSIONS
APPENDICES
REFERENCES
CHAPTER 6: ENZYMATIC REDUCTION OF POLGALACTURONIC ACID IN MECHANICAL PULP
