Research Results

High-performance plastics of polysaccharide ester derivatives

Bioplastics made from natural polysaccharidesFY2021

Iwata Tadahisa (Professor, Graduate School of Agricultural and Life Sciences, The University of Tokyo)
Development of advanced low-carbon technology, ALCA
Special Priority Research Area, "white biotechnology"
"High-performance polysaccharide-based bioplastics produced by innovative synthetic method and their application", Research Director (2015-2019)

Innovative synthesis method adds new features

Professor Iwata Tadahisa et al. of the University of Tokyo have developed an innovative high performance bioplastics from various polysaccharides obtained from natural biomass or by enzymatic polymerization. The polysaccharides include cellulose(β-1,4-glucan), derived from wood cell-wall, paramylon (β-1,3-glucan), photochemically produced by euglena, glucomannan, obtained from konjac potatoes, curdlan (β-1,3-glucan) and pullulan, produced by microorganisms, and β-1,3-glucan obtained by enzymatic polymerization.

They have synthesized various ester derivatives of these polysaccharides by precise chemical modification and eco-friendly and non-toxic enzymatic modification. The obtained bio-plastics exhibited novel unexpected properties that cannot be found in common petroleum-plastics, derived from their unique chemical structure of the original polysaccharide backbone.

The polysaccharide-based bio-plastics exhibited excellent mechanical strength, thermal stability, dimensional stability, durability, and unique optical properties, and these properties were precisely tunable by control of chemical structures of the ester groups and original polysaccharides. One of the successful examples for industrial application is the bio-plastics with “Urushi-black”, which is well-known as the color of Japanese high-quality lacquerware. The Urushi-black bio-plastics has luxury dark black in color and excellent mechanical strength and scratch-resistant property as well.

They are now focusing on creating novel polysaccharide-based bio-plastics with well-controlled appropriate properties for targeted purposes, and establishing their library for structure-property control. Their study will give promising solution for replacement of petroleum with biomass in current industries including plastics, medicine, foods, or other engineering.


Fig.1 Natural polysaccharides and enzymatically synthesized polysaccharide

Environmentally-friendly bio-based plastics

Global warming, depletion of petroleum, and environmental damages such as microplastics caused by petroleum-based polymers has been becoming a serious problem in last few decades. Bio-based plastics have been attracting much attention as an alternative to replace petroleum with renewable resources and to develop sustainable society. Bio-based plastics include two types of plastics. The first is biomass plastics which are made from natural resources such as plants and the second is biodegradable plastics which are decomposed by enzymes in the natural environment. Their study has been focusing on eco-friendly polysaccharide-based plastics, because polysaccharides are naturally abundant and biodegradable.

In terms of synthetic method, toxic metal catalysts has been used for synthesizing petroleum-based plastics, and harmful organic solvents have been used for extracting or synthesizing bio-based monomers in industry. In Prof. Iwata’s group, they have also been developing the consistent eco-friendly methods for enzymatic polymerization in aqueous solution, enzymatic esterification of polysaccharides, and enzymatic degradation, in order to reduce environmental impact of the bio-plastic production.

Their study is aiming for creation of novel high-performance and high-value-added plastics from polysaccharides, which exhibit unique properties or functions derived from the original chemical structure of polysaccharides, and which should be produced in eco-friendly ways.

Fig. 2

Fig. 2 Enzyme-catalyzed polymerization and non-solvent bulk polymerization

Good design-Good performance

Polysaccharides have high potential as raw materials for bioplastics, however, they have not been used so far because of difficulty of extraction, non-uniform structure, or impurities. In their study, various polysaccharide ester derivatives with different long or short side-chains was synthesized and they exhibited excellent heat resistant or impact resistant properties, or unique optical properties-depending on, their unique chemical structures of original polysaccharides or detailed combination of ester groups.

In general, when molding polysaccharide bioplastics such as cellulose acetate, petroleum-based plasticizers are added to improve processability, and large amounts of organic solvents are used for derivatization. In this project, the bioplasticss they developed had excellent processability and could be molded without any additives. In addition, they succeeded in reduction of organic solvent used in synthetic process and established low-energy bulk synthetic method.

For practical use of bio-plastics, both excellent-performance and excellent design are necessary. In this study, they have developed "Urushi-black” bio-based plastic , which has the color of Japanese traditional high-quality lacquerware. The Urushi-black bio-plastics is made of cellulose ester derivative, and has luxury dark black in color and excellent mechanical strength and scratch-resistant property as well. In order to maintain both aesthetic appearance and mechanical properties of the product, they developed novel method for blending additives to express its luxury black color, namely, low brightness, high glossiness, and other optical properties.

Fig. 3

Fig. 3 Cellulosic bioplastic with the beauty of lacquerware

High performance, environmental friendliness, and low cost

Various bio-plastic materials including films, fibers and molded products have already been produced besides “Urushi-black”, in this project, and their mechanical properties and molecular structures have been investigated as well. They are now aiming to further develop various bio-plastics from various unique polysaccharide with unknown and unexpecte properties including thermal, mechanical, optical, biological properties. They are also aiming to develop novel sustainable synthetic methods such as enzymatic polymerization for production of unique artificial polysaccharide backbone or non-solvent synthetic method for reduction of environmental impact.

The low-cost production of the bio-plastics are important concern in their study. They are now developing novel synthetic process to produce the polysaccharide-based plastics at low cost comparable with petroleum-based plastics for future application.