Research published in the Journal of the American Chemical Society found that carminic acid can be produced using metabolically engineered Escherichia coli (E. coli), which has unique potential for color cosmetics.
As industry consultant Kelly Dobos explained, carminic acid and carmine are two red colorants approved by the U.S. Food and Drug Administration (FDA) for use in cosmetics. Carmine acid, extracted from female cochineal beetles, is a dye used in foods and beverages, e.g., Campari liquor. In order to provide the desired benefits in cosmetics, carmine acid is laked onto a substrate of aluminum hydroxide, creating the pigment known as carmine.
Color Regulations and Biosynthetic Carmine
Colorants used in cosmetics face strict global regulations, and carmine is unique in that it is one of only two red shade pigments approved for use in the eye area (the other is Red 40 Lake) and that does not require batch certification.
According to Dobos, carmine is a bright blue shade of red that is also more amenable to create pink shades while Red 40 exhibits a brick red hue. Unfortunately, carmine's animal origin does not meet the requirements for cruelty-free or vegan claims, which poses a challenge for cosmetic chemists to create certain shades for eyeliners, eye shadows and mascaras. The new study, however, shows potential for a biosynthetic alternative.
As an aside, while the FDA and other regulations specify cochineal beetles as the source of carmine acid for the permitted carmine, Dobos noted both synthetic and natural sources for the color additive beta-carotene have been allowed, presenting a possible path and argument for the inclusion of biosynthetic carmine in cosmetics.
Fermenting Carminic Acid
According to the study, there has been much interest in producing carminic acid by fermenting engineered bacteria to alleviate the cumbersome process of farming insects. This would also bypass the multi-step purification process required thereafter. In cosmetics, a non-animal source for carmine would also provide a novel pigment shade that supports a vegan product claim.
As such, the authors sought to biosynthesize carminic acid from glucose in engineered E. coli. Through a series of optimization steps and biochemical reaction analyses, detailed in the article, simple metabolic engineering followed by fed-batch fermentation resulted in 0.63 ± 0.02 mg/L of carminic acid production from glucose.
The authors concluded the strategies described will be useful for the design and construction of biosynthetic pathways and production of diverse industrially important natural products.