Biopolymers - Food and Industrial Bioproducts and Bioprocessing - page 260

11 Biopolymers

O˘uz Türünç and Michael A. R. Meier

11.1 INTRODUCTION

It has been many years since human beings began using plant and animal products for
purposes other than nutrition, for example as paints or clothing. Since that time, the methods
and knowledge-base used to produce these products from such resources has steadily
developed. Eventually, the discovery of fossil oil and its consequent exploitation, including
the improved knowledge about petroleum chemistry and chemical engineering, resulted in
a “plastic revolution”, which first seemed to be very cheap, easily formed, and a long-lasting
technology. However, due to the recent awareness of not only the green house effect but also
accumulation of plastic waste in almost every part of the world, as well as environmentally
unsound production technologies, mankind has started to search for sustainable, environ-
mentally friendly feedstocks and technologies to improve the ecological impact of the
chemical industry. The fact that fossil oil is a limited feedstock only further clarifies the
need to develop more sustainable alternatives. Today, carbohydrate- and plant oil-based
polymers and synthesis technologies are being extensively researched and even commercial-
ized to some extent. This chapter summarizes current knowledge and applications of some
carbohydrate- and plant oil-based biopolymers derived from natural resources and discusses
possible future applications/products as well as properties of these materials.

11.2 CARBOHYDRATE-BASED POLYMERS

11.2.1 Polymers from starch
Starch is a highly abundant polysaccharide and is produced by plants to store energy. It is a
semi-crystalline polymer composed of amylose and amylopectin. Amylose is an almost
linear polymer consisting of

4) linked glucose molecules, whereas amylopectin has a
similar (1-4)-linked polymer backbone with an additional 5% (approximately)

α (1 →

6)
linkages with branches typically occurring every 24 to 30 glucose units (Figure 11.1) (Voet
et al ., 2006). The relative amounts of amylose and amylopectin depend on the plant source
and affect the final properties of the material. Corn starch granules for instance contain
approximately 70% amylopectin and 30% amylose (Avella et al ., 2005). Starch is one of the

α (1 →