When the oil runs out, it’ll be the small things you miss. Actually, given that petroleum is involved in almost every aspect of how food reaches me, I’ll probably miss that most. But if you want to use less petroleum now, let’s say, it’s almost impossible to say where to start—petrochemicals are used in everything from paint, to plastic, to fertilizers, and pharmaceuticals. You can pretty much start anywhere, really, and researchers at the University of California-Davis are starting with finding a new source for synthetic scents.
It’s estimated that 95 percent of chemicals used in fragrances are derived from petroleum, and while it might not compare to something like agriculture, scents and artificial flavoring are a $20 billion industry, according to Shota Atsumi, a UC-Davis chemistry professor. Rather than using petroleum, Atsumi and his team are attempting “to make chemicals from renewable sources instead,” he said. Naturally, when you think "good smells" you think, "what's in your colon;" so they’ve turned their attention to E. coli.
In nature, scents come from a class of compounds called esters, which are produced by reacting an alcohol with an organic acid. The ester isoamyl acetate smells like banana; methyl salicylate smells like wintergreen. Living cells also produce esters—yeast produces the esters that flavor beer and wine. Bacteria also produce esters that flavor, for example, cheeses. By altering what living cells naturally do, Atsumi and his team were able to change the type of esters that the bacteria were producing.
"The reaction is chemically difficult but biologically easy," Atsumi said. "Nature gives you a great system to work with."
The researchers were able to take genes from yeast and introduce them into E. coli, which was chosen not for its scent obviously, but because it has long been a model organism for biotechnology. They then could tweak the enzymes to alter the biochemical pathways in the cells, and manipulate the ester that was produced. Amongst laboratories that smell of sulfur, formaldehyde, and unwashed graduate students, the scent of banana, flowers and blueberry must have been striking as they wafted out of Atsumi’s lab. It certainly must have been an improvement over what E. coli typically smells like.
Their new technique has been patented and the study was published in Nature Chemical Biology, but the UC-Davis team isn’t the only one making a bacteria found in feces smell like roses. A team of bioengineers from MIT used metabolic engineering to make E. coli give off a synthetic banana smell, and nicknamed it "Eau d’coli".
While scents might seem like a fairly small part of life, the fundamentals of bioengineering that are uncovered while making E. coli smell better could find applications in bioengineered replacements for other industrial chemicals—for the paints, fertilizers, and whatever else.
While the E. coli were living off of sugars, Atsumi has been working with cyanobacteria, or blue-green algae, for a number of years. Cyanobacteria convert carbon dioxide into complex hydrocarbons, drawing their energy from sunlight.
Atsumi wants to figure out how to develop a synthetic organism that converts carbon dioxide directly into a biofuel, which sounds far off, but is nevertheless exciting. When the oil does run out, I’d like to still be able to have a banana every now and then, rather that just taking solace in an E. coli facsimile. Now that I think about it, I’d like to keep the amount of E. coli-based solace to minimum, regardless of how it smells.