Green Chemistry: Enzymes Are Playing A Larger Role in Green Chemistry

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Chemical manufacturing has seen large advances in so-called green chemistry in recent years. The term “green chemistry” has come to embrace some well-defined concepts in chemical manufacturing. As enunciated by Paul Anastas, considered by many to be the father of green chemistry,” a chemical process is greener when it meets certain well-defined criteria. Among those characteristics that enable a process to be called greener, many are commonsense goals. For example, a greener chemical process avoids the use of materials such a chlorinated hydrocarbons that are slow to break down or difficult to dispose of. Using solvents that are more biodegradable is preferred. Similarly, a process that reduces overall waste that includes all inputs into the process such as solvents, raw materials, and process aids. In addition, a green chemical process uses less energy and produces fewer greenhouse gas emissions. The greenness f a process is summarized by a term called the “E-Factor” which measures the total amount of solvents, reagents, and consumables used in kilograms and divides it by the kilograms of final product produced.

One technology that has become a central part of green chemistry is biocatalysis. Using enzymes, which are proteins that accelerate chemical reactions, has immediate advantages in turning a chemical process green. Enzymes are nature’s catalysts, present in every living organism to carry out a wide range of chemical reactions. As such, enzymes are completely biodegradable. In addition, because they are typically produced by fermentation from sugars, enzymes are truly renewable catalysts.

Increasingly chemical companies are looking to biocatalysis to improve the sustainability f their manufacturing. Nowhere have enzymes had a larger impact recently than in the pharmaceutical industry. Many drug substances are difficult to synthesize, requiring multiple steps, large amounts of solvents, and extensive purifications. Using enzymes as catalysts can improve the purity and reduce the amount of organic solvent needed, resulting in a much greener overall manufacturing process.

A good example of the impact of biocatalysis on pharmaceutical manufacturing is the recent announcement by pharmaceutical giant Pfizer about changes in its process for the production of pregabalin, the active ingredient in its $3 billion per year drug Lyrica. In 2007 Pfizer replaced a classical chemical processing step with a more efficient enzymatic step. The result is a 90% reduction in solvent, used a 50% reduction in starting material needed, and commensurately large reactions in other reagents and chemical inputs. The E-factor of the process was reduced from 86 to 9.

Biocatalysis has many attractive features in the context of green chemistry, and its impact will become significantly larger in coming years.

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