Presidential Green Chemistry Challenge: 2009 Greener Synthetic Pathways Award
Eastman Chemical Company
A Solvent-Free Biocatalytic Process for Cosmetic and Personal Care Ingredients
Innovation and Benefits: Esters are an important class of ingredients in cosmetics and personal care products. Usually, they are manufactured by harsh chemical methods that use strong acids and potentially hazardous solvents; these methods also require a great deal of energy. Eastman's new method uses immobilized enzymes to make esters, saving energy and avoiding both strong acids and organic solvents. This method is so gentle that Eastman can use delicate, natural raw materials to make esters never before available.
Summary of Technology: The cosmetics and personal care market is a vast enterprise of formulated specialty chemicals. Esters are an important class of cosmetic ingredients, comprising emollients, emulsifiers, and specialty performance ingredients. In 2006, the estimated North American consumption of esters as emollients and emulsifiers was 50,000 metric tons. Usually, such esters are manufactured using strong acid catalysts at high temperatures; unfortunately, this produces undesirable byproducts that must be removed by energy-intensive purifications. Other methods of producing cosmetic esters require organic solvents that are potentially hazardous to workers and the environment. The growing trend for natural ingredients and environmentally responsible processes in the cosmetics market requires new manufacturing methods.
In 2005, scientists at Eastman began investigating enzymes as catalysts to produce cosmetic esters. Eastman has now synthesized a variety of esters via enzymatic esterifications at mild temperatures. The esterifications are driven to high conversion by removing the coproduct, usually water from esterification of an acid or a lower alcohol from transesterification of an ester. The mild processing conditions do not lead to formation of undesirable byproducts that may contribute color or odor. The immobilized enzyme, such as lipase, is easily removed by filtration. The specificity of the enzymatic conversions and the relatively low reaction temperatures minimize the formation of byproducts, increase yield, and save energy.
Eastman's process can use delicate raw materials such as unsaturated fatty acids that would oxidize during conventional esterifications. Thus, Eastman can make ingredients never before available. It has manufactured hundreds of such new esters by combining different alcohols and acids. Biocatalysis can even yield new products that offer superior performance. For example, two esters can be formed from 4-hydroxybenzyl alcohol and acetic acid. One—esterification at the benzyl moiety—is only accessible via the enzymatic route. This particular ester inhibits tyrosinase, key enzyme in melanin synthesis, and, therefore, is effective in reducing undesirable skin pigmentation and providing a more uniform skin tone.
Eastman's biocatalytic process can save over ten liters of organic solvent per kilogram of product. The ester product is often pure enough to obviate post-reaction processing. An early lifecycle assessment identifies Eastman's process as vastly improved over conventional processes, especially in energy use. Overall, this process improves quality, yield, cost, and environmental footprint compared to conventional chemical syntheses.
Leading cosmetic companies are currently evaluating many of Eastman's new esters, including emollient esters made from rice bran oil, glyceride emulsifiers, and new ingredients that combat the visible signs of aging.
Podcast on the technology:(MP3, 1 MB, 1:07 minutes), Narrator: Dr. Richard Engler, US EPA.
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