Challenge of synthetic cellulose

Abstract

This article focuses on why and how the chemical synthesis of cellulose was accomplished. The synthesis of cellulose was an important, challenging problem for half a century in polymer chemistry. For the synthesis, a new method of enzymatic polymerization was developed. A monomer of β‐D‐cellobiosyl fluoride (β‐CF) was designed and subjected to cellulase catalysis, which led to synthetic cellulose for the first time. Cellulase is a hydrolysis enzyme of cellulose; cellulase, inherently catalyzing the bond cleavage of cellulose in vivo, catalyzes the bond formation via the polycondensation of β‐CF in vitro. It is thought that the polymerization and hydrolysis involve a common intermediate (transition state). This view led us to a new concept, a transition‐state analogue substrate, for the design of the monomer. The preparation of cellulase proteins with biotechnology revealed the enzymatic catalytic functions in the hydrolysis and polymerization to cellulose. High‐order molecular structures were in situ formed and observed as fibrils (cellulose I) and spherulites (cellulose II). In situ small‐angle neutron scattering measurements suggested a fractal surface formation of a synthetic cellulose assembly. The principle of cellulose synthesis was extended to the synthesis of other natural polysaccharides, such as xylan and amylose, and unnatural polysaccharides. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 693–710, 2005

Applications of Enzymes in Synthesis and Modification of Polymers

“…Neste caso, as moléculas devem ser desenhadas de acordo com um conceito de "substrato aná-logo ao estado de transição" (do inglês Transition State Analogue), de modo que sua estrutura deve ser similar à estrutura de transição encontrada nas reações enzimáticas presentes in vivo. 107 Esse conceito foi baseado no fato de que glicosil fluoretos e oxazolinas de açúcares são reconhecidos de forma eficiente como substratos por hidrolases. Há relatos na literatura que alguns polissacarídeos análogos à celulose e xilana já foram sintetizados via catálise enzimática a partir de monômeros glicosil fluoretos.…”

“…Há relatos na literatura que alguns polissacarídeos análogos à celulose e xilana já foram sintetizados via catálise enzimática a partir de monômeros glicosil fluoretos. 107 Já a partir do uso de oxazolinas de açúcares como monômeros, tem-se conhecimento da síntese das macromoléculas quitina, hialuronana, condroitina e derivados de aminopolissacarídeos. 108 Esse comportamento de catálise multi-funcional, que tem sido identificado em diversos tipos de enzimas, está muito além do conceito de chave-fechadura, que foi assumido durante décadas como o representativo da catálise enzimática.…”

A Hyaluronidase Supercatalyst for the Enzymatic Polymerization to Synthesize Glycosaminoglycans

“…This situation was explained by the "key and lock" theory proposed by Emil Fischer in 1894, that is, only the correctly shaped key (a substrate monomer) fits into the key hole (active site) of the lock (an enzyme), leading to a catalysis of a single reaction. [10][11][12][13][14] Recently, we have achieved the production of hyaluronan, [24] chondroitin, [25] chondroitin sulfate, [26] and their derivatives [25,27] by utilizing the catalysis of a single enzyme, that is, hyaluronidase (EC 3.2.1.35). [28] The single-enzyme catalysis enabled the production of various polysaccharides for the first time.…”

“…[10][11][12][13][14][15] This method enables a single-step production of a polysaccharide through polymerization of a simple sugar monomer activated at the anomeric carbon. For example, cellulose was synthesized by means of polymerization of b-cellobiosyl fluoride catalyzed by cellulase, [16][17][18][19] xylan by xylanase with b-xylobiosyl fluoride, [20] and chitin by chitinase with N,N'-diacetylchitobiose oxazoline.…”

New developments of polysaccharide synthesis via enzymatic polymerization

“…The discovery of the reaction (Scheme 3) much attracted chemists from many research fields 3) and actually initiated the series of our studies on ''enzymatic polymerization''; the cellulose synthesis opened a new door not only to synthesis of various polysaccharides but also to extensive synthesis of other polymers. These polymers include variously functionalized polyesters by lipase enzyme catalysis and oxidatively polymerized phenolic and polyphenolic substances by oxidoreductase enzyme catalysis.…”