Biocatalyst greenness

Excerpt

A very interesting inquiry into the use of biocatalysts is presented to illustrate how their use in synthetic chemistry schemes complies with the tenets of green chemistry. The qualitative aspects of green chemistry are eschewed in preference for quantitative or semi-quantitative methodologies to assess the environmental footprint via simple metrics such as the E factor (ratio of waste mass to product mass). Considerations important to the development of a useful metric are developed in a stepwise fashion. The article considers the “greenness” using water as a solvent, the effect of reagent concentration, neat reactions/water-deficient reaction media, and multiphase reactions for their roles in the identification of an environmental footprint. The article notes that biocatalyst preparation must be evaluated in detail for its contributions to the sustainability of synthetic application of the catalyst. Many biocatalytic reactions are based on established equilibria that may lead to the use of excess amounts of reaction substrate, in situ product removal, and smart co-substrates. Cofactor regeneration is important to many biocatalytic reactions and must be assayed for its contribution to the sustainability features. Downstream processing considerations loom as important components that can derail the effectiveness of a targeted chemical synthesis using a biocatalyst in terms of green chemistry tenets. The focus of the paper is the improvement of biocatalyst applications to make chemical synthesis more environmentally benign. …