Preface

Lignin , the second most abundant organic substance on earth, is one of the three structural polymers present in all woody plants. Lignin influences our world in many different ways. If it had not been for lignin, plants would never have moved from the aquatic to the terrestrial environment during evolution. It is lignin that "stiffens" the plant stem to withstand the forces of gravity and wind. Lignin seals the water conducting system against the hydraulic pressure drop produced by the transport of water from the soil to the leaves and needles. Although lignin provides plants with a protective barrier against the attack by microorganisms, it itself plays an important role as it is being recycled in the natural ecology: It serves the soil as a complexing agent for minerals and as a moisture-retention aid.

The chemical pulping of wood, one of the ten largest industrial activities in North America, involves the removal of lignin from wood. Commensurate with the size of the paper industry has been the scientific effort to understand the modification, depolymerization, and solubilization of lignin in wood. Utilization of this by- (or co-) product of the pulp and papermaking process has resulted in lignin being utilized in many diverse products ranging from road dust binder to a polymer component in printed circuit boards. More than one million tons of lignin are now being sold annually worldwide, thus making this by-product an industrial commodity.

Despite this important role of lignin, however, many uncertainties remain in our understanding of lignin's structure, process of formation, analytical recog­nition, and behavior in wood, pulp, and human-made materials. These uncer­tainties continue to be addressed with new scientific methodologies and shifting environmental and ecological concerns. This new research, which combines modern and traditional structural analysis techniques and which makes use of novel experimental protocols emerging from the fields of biotechnology and materials science, are beginning to provide exciting possibilities for recognizing the "true" structure of lignin, and of its behaviors during pulp and paper produc­tion and as a contributing constituent of non-woody materials. Much recent research has focused on opportunities for genetically manipulating wood for­mation in such a manner that lignin becomes easier to remove in environ­mentally-benign pulping operations. The use of lignin as a low-cost material continues to energize research into developing new lignin-based products. The

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multifaceted task of understanding lignin's formation, structure, and its reactions and behaviors during pulping, bleaching, and modification continues to attract the attention of scientists in all disciplines. Because these scientists have diverse scientific, engineering, and business interests, this research creates opportunities for broad discussions on many diverse issues dealing with lignin.

This book was developed from a symposium by the American Chemical Society's Cellulose, Paper, and Textile Division honoring the 1997 Anselme Payen award recipient, Joseph L . McCarthy, held at the 215 t h National A C S Spring meeting in Dallas, Texas. The Symposium provided a forum for organ­izing an integrated discussion of our current knowledge on lignin, and on its historical roots. It brought together international scientists from academia, government, and industry to discuss new insights and commercial developments on lignin. This book is divided into five sections: History and Structure, Biochemistry, Analysis, Modification and Utilization, and Pulping and Bleach­ing. Each section has at least one overview chapter, a comprehensive review written by one or several recognized experts that is followed by chapters dealing with current research findings.

The first section, History and Structure, provides an authoritative per­spective on more than 50 years of scientific and engineering endeavors dealing with lignin structure, response to pulping and bleaching, and modification and utilization. The chapters dealing with biochemistry display the current under­standing of biochemical pathways leading to precursor formation and the en­zymes involved in the production of a cell-binding polymer of considerable nonuniformity. The chapters summarizing analytical advances address both chemical and molecular identities. The section on modification and utilization defines current practice and reviews recent advances in polymeric structure modification and utilization. The wide field of lignin reactions during pulping and bleaching are highlighted in the final part.

It is the hope of the editors that this book wi l l provide practicing scientists with new ideas for studying or utilizing lignin, and also to furnish graduate students with a resource by which they can explore this yet under-understood biopolymer.

Acknowledgments

The editors express their appreciation to the A C S Cellulose, Paper, and Textile Division for sponsoring this symposium. Thanks also are given to the Georgia-Pacific Corporation, Westvaco, Weyerhaeuser, and the academic institutions of the editors for their financial and editorial support. The editors also wish to thank Anne Wilson and Kelly Dennis of the A C S Books Department for their competent and professional support and encouragement. Finally, the editors acknowledge the time and effort, which many of our professional friends

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contributed through the process of reviewing, critiquing, and otherwise im­proving this most recent contribution to the A C S Symposium Series.

WOLFGANG G. G L A S S E R

Department of Wood Science and Forest Products Virginia Polytechnic Institute and State University Blacksburg, VA 24061-0324

R O B E R T A. N O R T H E Y

Paper Science and Engineering Division College of Forest Resources University of Washington Seattle, WA 98195

TOR P. S C H U L T Z

Forest Products Laboratory Forest and Wildlife Research Center Mississippi State University Mississippi State, MS 39762-9820

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