The concept of sustainable development has become the focus of both the industrial world and society. The production of chemical compounds and their application, whether on an industrial scale or on a small scale in academic research laboratories, has been undergoing a paradigm shift in the 21st century, with "sustainability" as the driving force. One way to achieve this much-desired goal is to implement the principles of Green Chemistry as a routine working tool, which advocates, among other things, the use of catalysts instead of stoichiometric reagents.
The use of catalytic technologies increases the eco-efficiency of products and processes by optimizing resource use and minimizing waste generation and environmental impact. One of the currently available catalytic technology options is Biocatalysis, which uses enzymes to catalyze chemical reactions. Compared to other types of catalysts such as transition metals and organometallic compounds, enzymes offer significant advantages:
- They are very efficient and can therefore be used at concentrations as low as 10-3-10-4 mol %, while metal-mediated catalytic processes require around 0.1-1 mol % of catalyst;
- They are highly selective: chemo-, regio-, diastereo-, and enantioselective;
- They are environmentally acceptable due to their total biodegradability;
- Enzymes operate under mild reaction conditions with pH levels typically ranging from 5-8 and temperatures between 20-40 °C, which minimizes issues with unwanted side reactions;
- Possibility of cascade reactions in a single pot since enzymes generally function under similar reaction conditions;
- Enzymes are not restricted to their natural substrates and can catalyze a wide range of reactions. There are enzymatic equivalents for almost all known organic reactions such as: hydrolysis or synthesis of esters, amides, lactones, lactams, ethers, acid anhydrides, epoxides, and nitriles; oxidation of alkanes, alcohols, aldehydes, sulfides, sulfoxides; epoxidation of alkenes, aromatic compounds, hydroxylation, and dihydroxylation, Baeyer-Villiger oxidation of ketones, reduction of aldehydes/ketones, alkenes, reductive amination; addition-elimination of water, ammonia, hydrogen cyanide; halogenation and dehalogenation, Friedel-Crafts alkylation, dealkylation, carboxylation, decarboxylation, isomerization, aldol reactions. Even Michael additions, Stetter reactions, Nef reactions, and Diels-Alder reactions have their enzymatic versions.
In a biocatalytic reaction, enzymes can be used in isolated form, as a crude enzymatic extract, or even the microbial or plant cells themselves that contain a vast enzymatic machinery at our disposal. We can also consider various alternatives to improve the performance and stability of enzymes and/or the process, such as the use of immobilization methods that allow the reuse of biocatalysts, replacing the aqueous medium with unconventional media such as ionic liquids, supercritical fluids, multiphase systems, using molecular biology tools to create enzymes more suitable for the reaction or process in question, among others.
Biocatalysis reactions have been successfully used in various areas of chemistry and are now a reality in the production lines of multinational industries, as well as medium and small enterprises for the organic synthesis of compounds of pharmaceutical interest such as the chemotherapeutic agent Taxol®, production of chemical commodities like acrylamide, in the textile industry during the stages of hair removal from fibers, decolorization, and washing of jeans, in the cellulose paper industry during pulp bleaching, in agribusiness, in medicine, in the mining industry, and in the food and cosmetics industries with the production of flavors, etc. All this without mentioning applications related to bioremediation and biodegradation of toxic pollutants.
In short, Biocatalysis is an attractive, feasible alternative that has been adopted by industries in different sectors seeking not only to minimize the waste generated, optimize their processes making them more efficient and/or less harmful to the environment but also to offer their consumers quality products with greater added value due to sustainable production. After all, being sustainable or not depends on our daily choices.
Cíntia Milagre is a researcher at UNESP, in the Department of Biochemistry and Microbiology. She completed her doctorate and postdoctoral studies at Unicamp in biocatalysis, and in 2011 studied at Delft University of Technology during her second postdoctoral fellowship.
References:
Meyer, H-P; Eichhorn, E.; Hanlon, S.; Lutz, S.; Schurmann, M.; Wohlgemuth, R.; Coppolechia, R. Catal. Sci. Technol. 2013, 3, 29.
Sheldon, R. A. Green Chemistry 2012, 41, 1437.
Bornscheuer, U. T.; Huisman, G. W.; Kazlauskas, R. J.; Lutz, S.; More, J. C.;
Robins, K. Nature 2012, 485, 185.
