Application of Biocatalysis in Polymer Synthesis

Review and progress.

The application of biocatalysis in polymer synthesis Li Zuyi, Chen Ying (Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China) pays more attention to the fact that the stereoselectivity of biocatalysts is one of their main advantages, and new or improved methods emerge one after another. The process of biocatalysis mainly focuses on several aspects: polymerization reaction, polymer modification reaction, polymer degradation reaction, and synthesis of monomers and oligomers. In this article, we summarize the latest applications of biocatalysis in polymer synthesis.

Polymer materials are a class of extremely important chemical substances. They are widely used in people's daily lives and the national economy. Industry has begun to replace steel with plastics and fibers. The daily metabolism in the pharmaceutical industry, the perfume industry, and even in our body is also a series of chemical reactions related to macromolecules.

Polymer compounds occupy an irreplaceable position in the national economy and people's daily lives. Common polymer synthesis reactions require temperature control, pressure control, high equipment requirements, and low output. With the in-depth research of scientists and the need for large-scale industrial production, it is required to change the activity of the reaction system and use a variety of catalysts in order to increase production and reduce production costs. The 21st century is an era of green chemistry, environmental chemistry, and economic chemistry. The use of new non-toxic, low-damage catalysts and the use of highly efficient catalytic methods to synthesize the required macromolecules are the trend of polymer synthesis research.

As an important part of the study of green chemistry, the use of biocatalysts for the synthesis and modification of polymers is becoming another new research hotspot in various developed countries. Biocatalysis must be accompanied by the use of whole cells and enzymes, and through them chemical reactions and treatments. In nature, these biological reactions are ubiquitous, and in fact there is no life without them. The potential role of these reactions in organic synthesis has been known for some time, and this can be demonstrated in numerous publications that o-ch3 can form polymers when the reactants are unsubstituted monomers. Substitution on the monomer will lead to lactone formation (through intramolecular cyclization).

In Brandstadt et al., the self-condensation of 12-hydroxylauric acid under different reaction conditions was studied using porcine pancreatic lipase. From 4 (1) to 12500 Mn, 12-hydroxystearic acid with a secondary alcohol did not polymerize. 1.1.2 Different monomeric polycondensation enzymes can be used to catalyze the polycondensation of oligoesters and polyesters formed from diacids (BB) and diols (AA). This type of polymerization is sometimes referred to as polyester exchange.

If the diester is used instead of the diacid, the reaction will be facilitated, while if the diester is activated, the reaction (for example, enol or vinyl ester) will be further promoted.

One may have noticed that traditional chemical and enzymatic methods can be used for the polymerization of 4-, 6- and 7-membered lactones (m = 245) 8. For macrolides (m>9), Chemical methods result in lower reaction rates and lower molecular weight polymers; in contrast, enzymatic polymerization results in faster reaction rates and higher molecular weight polymers. Kdbayashi et al.

Kobayashi reported in his article the synthesis of 3-butyrolactone/caprolactone and ecaprolactone W2-docecanoHde copolyesters, and investigated their enantioselectivity, solvent media and reaction as a monomer structure function. time.

(from Novozymes A/S) copolymerization, random copolymers can be obtained.

Kobayashi. An example of simultaneous copolymerization of macrolides, diethyl esters, and ethylene glycol with the help of a lipase (lipase PC) is given below.

The ability of transesterification between polyesters. Thus, in the presence of Novozym-435, the transacetylation reaction occurs when a large amount of polyhexenolide and polycaprolactone are heated to 7075°. Based on the molecular weight of the starting polymer and the reaction time, the resulting copolyester may have multiple distributions (in the case of high molecular weight polymers and short reaction times) or a random distribution (at long reaction times). In Kumar et al.

Steinbtichel reviewed his work in the article on the metabolic engineering of polyhydroxyalkane biosynthetic pathways. He first demonstrated that a biosynthetic pathway using pure enzymes is operational in vitro. He then proposed a new in vivo pathway in the E. recombinant strain. The gene was cloned into a plasmid and the recombinant cells were cultured. When the corresponding hydroxy fatty acid was added, homopolyester and copolyester were found.

Different composition of the PHA system. The resulting structure is similar to phenolic resin. Therefore, these reactions are considered as substitutes for Novalac resin but do not contain formaldehyde.

Kobayashi et al. revealed the role of laccase and oxygen in the polymerization of 2,6-dimethylphenol. Most of the reports involved acrylic systems. Kalra and Gross's article made a good comment on this reaction. This polymerization can be carried out in solution or in emulsion. Polyacrylamides and polyacrylates are atactic but methyl polymethacrylate is ectopic.

3 Synthesis of oligosaccharides and polysaccharides Due to the presence of various hydroxyl groups and stereochemical structures, polysaccharides and oligosaccharides are a very troublesome compound for chemical synthesis. In general, such reactions require time-consuming and laborious protection and deprotection steps in addition to pharmaceuticals and other high-end applications. It has been found that enzymes are a potentially cheap alternative. Wong, Whitesides and others have extensively applied these techniques to the synthesis of carbohydrates and oligosaccharides. The role of hydrolytic enzymes in the polymerization of fluorinated disaccharides into natural and non-natural polysaccharides has been reported. An example is fiber. Because once the degree of polymerization (DP) reaches 810, cellulose will be economically viable from solution, and these methods must show better precipitation than the corresponding chemical methods and therefore have lower molecular weight.

Xylan, DP-23) and the azoline (GKazoline) derivative TV, A diacetylchiose (forming high molecular weight chitin) were obtained.

Department. Several examples will be given here (in four categories).

4.1 Chiral monomers Many reactions utilize the stereoselectivity of enzymes to produce monomers suitable for polymerization. An example of a stereoselective monomer is a lactone. Lipases in organic media have been successfully applied to the lactonization of Y-hydroxy esters, -hydroxy esters, and e-hydroxy esters (=2,3,4) to produce corresponding stereoselective lactones for use. The paint remover extract from Aabidopistha/iana synthesizes guaiac dextran and synthesizes cellulose with an extracellular extract from Rubus/iut/msus.

4 Synthesis of Monomers and Oligomers The patent work gives more examples of the synthesis of monomers through biocatalysts. For example, General Electric: The company uses enzymes for chiral resolution by the asymmetric hydrolysis of racemic diesters to produce optically active binaphthols. This reaction product can be conveniently treated with alkali to produce epichlorohydrin, thereby recycling the waste product and increasing the overall yield of epichlorohydrin.

Microbial methods can often achieve monomer polymerization that is difficult (or impossible) to achieve with conventional chemical methods. For example, Lau et al. Then the monomers are polymerized.

Another example is the attachment of vinyl acrylate to sucrose in pyridine. The resulting acrylate is a superabsorbent polymer aw after polymerization. An excellent example of an industrial application is the silicone acrylate paint additive manufactured by Degussa AG. Corresponding chemical reactions typically require temperatures above iro and require a radical scavenger to stabilize the reaction mixture to suppress undesired polymerization reactions. In many applications, the chemical catalyst must be removed, which adds to the cost. The color of the reaction mixture will also increase. Enzymatic processes (using lipases, esterases, or proteases) can avoid all of these problems.

4.4 Oligomeric macromers and low molecular weight polymers can polymerize or otherwise react with macromolecules. For macromonomers, a preferred reaction is the ring-opening polymerization of lactones. Therefore, in an article by Kobayashi et al., they used lipase-catalyzed conversion reactions to create a well-defined macromonomer around the sugar core. This method is adjustable and can be used to produce a wide range of macromonomers.

5 Enzyme-catalyzed polymer modification Since the enzyme reacts with organic compounds with small molecular weights, the same reaction can generally be applied to polymers with large molecular weights. The main purpose is to improve the properties of the polymer to add value for its particular application. So far, most of the articles in this field deal with water-soluble polymers, especially polysaccharides. Some of the modification reactions are summarized in Table 1. It also gives some interesting properties and typical applications.

The article gives examples of many polysaccharide modifications, including charge addition, addition (or removal) of polar groups, hydrophobic modification, and redox reactions. In addition, Xe and Hsidi use tyrosine to attach hydrazine and some peptides to chitosan (polyglucosamine). 55 Lipase is used to attach the hydrophobic ester to the cellulose derivative. Hu et al.

6 Degradation of Polymers There are many enzymes in nature that can decompose substances, and therefore there are often enzymatic reactions in hydrolysis and degradation. As a result, hydrolytic enzymes are often involved. As we all know, lipases and esterases can degrade some polyesters, proteases can degrade proteins, amylases can degrade starches, cellulases can degrade cellulose and cellulosic derivatives, and many other enzymes target other natural Polymeric substrate. Although these polymers can be chemically degraded (such as acid or base hydrolysis), enzymatic methods have milder reaction conditions, lower temperatures, and fewer by-products. In addition, because many enzymes have their specific reaction patterns or sites for hydrolysis, the enzyme degradation products sometimes differ from the structures of chemical degradation products. One example is the hydrolysis of carboxymethyl cellulose (CMC) by cellulase.