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Cyanobacterial polysaccharide : a huge tribute from the biological ancestor
Cyanobacteria are the oldest photosynthetic organisms which emitted a large amount of oxygen into the earth atmosphere, to make other creatures live on the ground. It is amazing that cyanobacteria are living still now to produce various metabolites which protect their own cell body. Especially extracellular polysaccharides (EPS) formed jelly matrixes surrounding the cell bodies to protect themselves from various biological and physical stressors for a pretty long time. Then cyanobacterial EPS must haveuseful functions inducing as an environmentally-benign resource for functional materials. However almost all of the cyanobacteria with jelly matrix could not be cultivated and then the materialization of their metabolites were difficult.Here we focused on Aphanothece sacrum which is a traditionally-cultivated cyanobacterium in a southern area in Japan, and which produced a large quantity of EPS to form big jelly matrixes. The novel, giant EPS with a molecular weight over 107 g/mol was extracted from the extracellular matrix of the cyanobacteria. Some unique properties resulting from the high molecular weight were found.Furthermore, we will show various unique polysaccharides derived from other cyanobacteria in the seminar.
Bioplastic wonderland established based on multifunctionality of aromatic biochemicals
The significance of renewable biochemicals is increasing year by year while the seriousness in the earth environment is escalating. Especially biochemicals can contribute to low-carbonation in materials processing and waste reduction in the materials deposition. However, most biochemicals difficultly receive chemical treatments due to their complexity of structures such as multi-functionality and multi-reactivity. If the multi-reactivity was controlled, new functional materials may be developed. For example, sucrose has 8 hydroxyls and 3 ethers but it is highly bioavailable to materialize as a sweetener. If sucrose is produced by petro-chemistry, the production cost will be too high to develop it. In our study, we prepared bio-based plastics based on the multi-functionality and multi-reactivity of biochemicals. Caffeic acid, which has 2 hydroxyls and 1 carboxyl and is bioavailable from coffee beans and other variousbiomaterials, was used as an AB2-type multifunctional monomer to create the branching point in the polymer backbone. Then we produced high-heat resistance and environmentally-degradable plastics composed of the hyperbranching polymers containing caffeic acid branches, and other materials such as photo-functional biopolymers and high-performance bio-adhesives.
1) T.Kaneko, et al. Nature Mater. 5(12), 966-970 (2006).
2) T. Kaneko, Chemical Record, 7(4), 210-219 (2007).
3) K. Yasaki, T. Kaneko et al. J. Polym. Sci. Part A Polym. Chem. 49(5), 1112–1118 (2011).
Ces séminaires sont proposés par le laboratoire PPMD/Sim