Many companies wishing to become more sustainable choose to go along the route of solvent reduction.

Many companies wishing to become more sustainable choose to go along the route of solvent reduction, and this featured heavily in the 2004 awards given out by the US Environmental Protection Agency (US EPA) as part of its presidential green chemistry challenge.

Bristol-Myers Squibb (BMS) received the alternative synthetic pathways award for developing a more environmentally friendly way to make its anti-cancer drug Taxol using plant cell cultures.

Paclitaxel, Taxol’s active ingredient, was first identified and isolated from the bark of the Pacific yew tree over 30 years ago. Extracting the compound from the trees proved a tricky business and in 1991 BMS came up with a semi-synthetic way to produce it using leaves and twigs harvested from European yew trees. This method was still not ideal, because of the amount of land required to grow the trees and the use of a large number of solvents and organic reagents. The plant cell culture technique, which was developed with a firm called Phyton Biotech, removes 10 solvents from the process and enables paclitaxel to be fermented all year round.

Meanwhile, Charles Liotta and Charles Eckert from the Georgia Institute of Technology received the US EPA’s academic award for developing benign tunable solvents that can be used in both the reaction and separation stages of a chemical process. For example, they have carried out a wide variety of synthetic reactions in near-critical water, which when heated to 275°C under pressure dissolves non-polar organic chemicals that would be insoluble under normal conditions. In acid and base catalysis, near-critical water eliminates the need for a neutralisation step and prevents waste salts from forming. They also worked extensively with supercritical CO 2, and used CO 2-expanded liquids to ease recycling of homogeneous catalysts.

Awards also went to Buckman Laboratories for an enzyme technology to improve paper recycling; Engelhard Corporation for developing organic pigments without Pb, Cr or Cd; and Jeneil Biosurfactant for developing a natural low toxicity alternative to synthetic surfactants.

Emma Davies