SITTING before me is a vial of cloudy white broth. Biologist Patrick Boyle invites me to take a sniff. To my amateur nose, the liquid smells green and sweet, a little like fresh-cut grass, a little like a bunch of flowers.
The concoction is a microbial perfume. Cooked up in the laboratories of in Boston, it contains yeast that has been genetically engineered to smell of roses. Its ultimate purpose: to become part of a designer fragrance, one where its presence rivals the rose oils often used in luxury scents.
The 鈥渃ultured rose鈥� was born out of a marriage between Ginkgo 鈥� which bills itself as 鈥渢he world鈥檚 first organism engineering foundry鈥� 鈥� and , a French flavours and fragrance company founded in 1850. Robertet prides itself on the natural ingredients it uses in perfumes created for , as well as its scents for household products like detergents.
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Rose oil is a classic perfume component. Traditionally, roses are grown in vast fields in Bulgaria or Turkey, then picked by hand and distilled to extract the aromatic oil. But from the fragrance companies鈥� perspective, this approach is unreliable. Both the quality and the price of roses can fluctuate wildly from year to year, influenced by factors such as natural disasters, labour shortages, diseases or simply a poor growing season. 鈥淵ou have raw materials that will go from $10 to $100 a kilo because there鈥檚 a shortage or an embargo,鈥� says Bob Weinstein, chief operating officer at Robertet.
Perfumers can use a synthetic substitute, created by mixing four or five chemicals together to approximate natural rose scent. This can be convincing, but some perfumers say it falls short of the rich subtleties that would distinguish a high-end fragrance.
Culturing microbes to produce scents is not only cheaper than using naturally sourced ingredients, but also gives perfumers more control over fragrances, says Ben Fundaro, director of perfumery at Robertet. 鈥淲e鈥檙e basically at the mercy of nature with some of these crops,鈥� he says. 鈥淚f we could produce in a more controlled environment, the odour would be more consistent.鈥�
鈥淲e鈥檙e at the mercy of nature with roses. Cultured products would give us a more consistent odour鈥�
The approach being pursued at Ginkgo starts with the DNA of the rose itself. In order to make the compounds responsible for their flowers鈥� distinctive smell (see 鈥�On the scent of a rose鈥�), plants need to use enzymes, and the team must find the genes coding for these. Once that鈥檚 done, Ginkgo can engineer a number of strains of yeast, each with a genome modified to ensure that the microbes鈥� metabolic reactions result in one of the desired compounds. This might be accomplished by tweaking the genome or by adding genes from a rose or another plant, such as corn or hyacinth, that does the same job.
鈥淥ur goal is to recreate the rose biosynthetic pathways, even if we don鈥檛 use rose genes to do it,鈥� says Boyle. 鈥淲e often find that a different but highly related gene from a different species works better in yeast than the rose gene that has the function we want.鈥�
Every month or so, Ginkgo sends samples of the strains to Robertet perfumers. They evaluate them and send critiques back to Ginkgo, asking for a scent to be made stronger or weaker, or to play up its floral, musky or fruity qualities. Once the strains for the individual components have been cleared by the perfumers, Ginkgo will produce a single strain of yeast that has all the genetic modifications 鈥� their attempt at the ideal rose scent.
The best rose oil, says Fundaro, smells fresh and clean, 鈥渧ery true to the way the rose would smell in the air if you were in a rose garden or next to a bouquet鈥�. One issue with the cultured rose fragrance is that it retains the yeast鈥檚 characteristic sour smell. Before Boyle鈥檚 team is done, they must find a way to downplay this odour, perhaps by moderating some of the genetic pathways that contribute to it, or by carefully filtering the final product.
Ginkgo isn鈥檛 the only company to have anticipated manufacturers鈥� desire for cultured fragrances and flavours. Californian company Amyris has partnered with Swiss firm Firmenich to work on lab-made patchouli oil. Allylix, another California company, cultures a version of vetiver oil, a woody extract of an Indian perennial grass.
鈥淭he basic material is sugar and microorganisms, so it鈥檚 much more stable,鈥� says Toine Janssen, CEO of Isobionics, based in Geleen in the Netherlands. Isobonics relies on bacteria to make valencene, a compound found in oranges and often used in soft drinks. 鈥淚t鈥檚 like brewing beer. If you have lots of fermenters, you can make as much as you like.鈥�
, a chemist at the University of California, Davis, sees another potential upside to cultured products: they may replace some synthetic scents, the vast majority of which are produced from petrochemicals. Last year, in an effort to demonstrate the potential of cultured scents as a renewable alternative, Atsumi鈥檚 research team of E. coli to make the bacteria smell like bananas and blueberries.
It鈥檚 not clear what customers will make of a microorganism-cultured perfume. , a perfume industry analyst, says companies may choose not to highlight the unusual product process on the label. 鈥淔or reasons of intellectual property, the fragrance industry doesn鈥檛 share the components of perfume, much less how they are synthesised,鈥� she says. 鈥淗ow would anyone know that the molecules in their eau de toilette are yeast-produced?鈥�
As researchers get better at producing cultured fragrances, they may become more adventurous, attempting to replicate much scarcer ingredients. Many natural fragrances prized by perfumers are extremely difficult to get hold of: compounds from jungle orchids that resist cultivation, for example. Another rare ingredient is ambergris, an earthy substance made inside a sperm whale鈥檚 guts; people collect it whenever it washes up on the beach. These could one day be cultured by comparing the genomes of their animal and plant sources to ones already on tap in the lab.
Or fragrance companies could turn to bioengineers to order custom-grown versions of scents. This is the idea that excites , a perfumer for over 40 years. 鈥淧erfumers get inspired by nature,鈥� says Gras. 鈥淚 can imagine with genetic engineering, you can make new odours just by changing the genes of the flower. It is another way of thinking.鈥�
The biologists at Ginkgo plan to push these boundaries. They are now seeking samples of Ice Age wildflowers that have been preserved in permafrost. If the surviving DNA fragments contain genes present in modern-day plants, researchers may be able to develop a yeast strain that mimics the extinct plants鈥� long-lost fragrances.
鈥淐an we recreate the scent of flowers that can鈥檛 be grown because they don鈥檛 exist any more?鈥� asks Boyle. 鈥淧eople have sequenced Neanderthals, so it鈥檚 not out of the question.鈥� Parfum Extinctio, the ultimate elite fragrance.
鈥淐an we recreate an extinct flower鈥檚 scent? We鈥檝e sequenced Neanderthals, so it鈥檚 not out of question鈥�
On the scent of a rose
Why does a rose smell like a rose? To uncover the secrets of a flower鈥檚 scent, chemists use a technique called headspace analysis. They lock the plant in an airtight glass container, trapping the volatile components responsible for its smell. It鈥檚 then easy to do tests to identify each compound and measure its concentration.
Headspace analyses have revealed hundreds of compounds among the different rose varieties. The most common contributors to the classic rose smell are:
Citronellol Also found in citronella candles. Imparts a sweet smell.
Geraniol Strengthens the rose scent.
Nerol Makes roses smell fresh.
Farnesol This sweet-smelling compound in combination with the three above give roses their characteristic smell.
Linalool Often used in cleaning products with floral fragrances.
Eugenol Also found in bay leaves and clove oil, it has a spicy smell.
Rose oxide Has a grassy smell; strengthens roses鈥� initial fragrance, or top note.
This article appeared in print under the headline 鈥淵east鈥檚 heavenly potential鈥�