Stephen Gravina, Ph.D.—
Discovering Flavor Enhancers Using Genetic Technology
Stephen Gravina, Ph.D., is the Associate Director of New Jersey-based Linguagen Corp., one of the leaders in the burgeoning field of genetic-based flavor enhancement. Linguagen presently holds the patent for gustducin, a G protein key to the physiological function of taste, and is hard at work obtaining G.R.A.S. certification for a natural “bitter blocker” for use in the taste enhancement of everything from children’s cough syrup to artificial sweeteners to oral AIDS medications. Gravina has been with Linguagen since 1997. He earned his Ph.D. in Pharmacology from Case Western Reserve University.
FoodTechSource: How long has Linguagen Corp. been in business?
Stephen Gravina: Since 1995. Dr. Bob Margolskee founded the company. He brought in Richard Lufkin as business manager, and Scott Linthicum, a professor at Texas A&M University, to serve as President. Margolskee came to the table with patents for gustducin, which is a key G protein involved in taste. He basically discovered it while at the old Roche Institute in Nutley, New Jersey—which closed, didn’t know what to do with the patent, and gave it to him. One of Margolskee’s key findings was that if you take a mouse and remove the gene for gustducin they are unable to taste a bitter flavor. They drink bitter compounds like it was water. That was key evidence the protein was critical in transducing bitter taste.
FTS: You mean gustducin inhibits the ability to taste bitterness?
Gravina: No, it was the lack of gustducin. The mice without the gene for gustducin could not taste bitter. They didn’t taste sweet very well, either. But they did taste salty and sour just fine.
FTS: What is the company doing with that patent?
Gravina: We are involved in the commercialization of new flavors and flavor modifiers, and in discovering new flavor modifiers by utilizing the proteins we’ve isolated. So, let’s take a typical flavor house like IFF—if a company comes to them and says we have a chip we want to make taste a little different, they will just go to their inventory of flavor compounds and pull a few off the shelf and add a little flavoring to cover up the bad taste. What we would do is use a biochemical assay to identify the compound that is causing the bitterness, then run it through a system to determine the best blocker to use to get rid of the bitter taste. In fact, bitter blocker is the first commercial product we have developed.
“We use a biochemical assay to identify the compound causing the bitterness, then determine the best bitter blocker to use.”
FTS: Once you isolate the protein, how do you determine which blocker to use?
Gravina: You screen random chemical libraries—if you screen enough compounds, eventually you will find one that does what you want it to. We are also looking at G.R.A.S. compounds—naturally occurring compounds “Generally Recognized As Safe.” Those compounds can be taken to market very quickly because you need only limited FDA involvement to gain approval. In fact, we recently discovered one that can be used as a blocker.
FTS: Is that the one I’ve read about that is going to be added to cough syrup?
Gravina: Yes, we’d be looking at cough syrup for babies, and AIDS medications—AIDS medications taste horribly, horribly bitter. Many of them are given in an oral suspension. The poor AIDS sufferers have to take this bitter medication every three hours for the rest of their lives. It makes them feel extremely ill. And the flavor houses are at a loss what to do. They’ve tried adding syrup, they put in cherry juice, they put in sugar, but there’s only so much you can do to mask a flavor. What we’re doing is going right to the center of things and blocking right at the receptor.
FTS: So let me get this straight: your blockers lock onto the taste receptors and “occupy” them so that the taste of bitter can’t be detected.
Gravina: Basically that is correct, but let me explain the way bitter works. Let’s say you take an oral decongestant. It’s a single molecule, it enters into your mouth and it binds to the receptors on taste buds. Taste buds are the specialized group of cells that basically figure out what’s in your mouth, whether it be hot, cold, salty, sour, bitter, sweet or even a new flavor people call umami—sort of the savory taste of fish. If the oral decongestant is a bitter molecule it will bind to the bitter receptor on the surface of the taste bud cell—on the taste receptor cell. What it does there is cause a change in that protein, which activates the gustducin—the next protein in the pathway. The gustducin then goes on to spark a whole series of events changing the cellular function, which causes the cell to send a signal to the brain saying “Hey, this is bitter.”
“There’s only so much you can do to mask a flavor; instead, we are blocking it right at the receptor.”
FTS: And you hold the patent on gustducin?
Gravina: Yes, we do. If you want to use that biochemical pathway in a test tube, you have to go through gustducin, and we own the patent for that. But people are more likely to come to us to license the related assay. It is a biochemical test that when you throw a bitter compound in and shake it up in the tube it turns blue. Then you can try various blockers, and when you find one that works it stops it from turning blue.
FTS: And you own the patents on the assays?
Gravina: Yes, the gustducin patent covers the use of gustducin in the assay. So we’ve got patents on that and on the blockers we’ve discovered. We’ve also discovered some new ones that we are in the process of patenting.
FTS: What are some of these new bitter blockers?
Gravina: The blockers we’re looking for right now are small, naturally occurring molecules—and the one we found is in all living things. It’s called Adenosine 5-monophosphate—AMP for short. You find it in yeast, for example. It’s one of the pre-metabolic precursors for ATP. It is very effective in reducing the bitter taste of various drugs and quinine. We’re researching its use with antihistamines, so we’re right in the process now of making sure that it’s safe. We know that it’s effective.
FTS: Is it G.R.A.S.-certified?
Gravina: Not yet. We are actually getting the application together as we speak for this September, which is when the G.R.A.S. committee next meets. We hope to be able to give them our application then.
FTS: What then? Does Linguagen license AMP to drug manufacturers or food manufacturers who are trying to get rid of bitterness in their products?
Gravina: Exactly right. We would be looking for licensing and usage agreements.
FTS: So, you don’t produce it you just own the patent to it and license its use?
Gravina: Yes. And our lab is hard at work looking for the next generation blocker. Of course, the next generation will be much more high-affinity, more directed, and we will probably need to secure a new drug application from the FDA—which will require a large sum of money and take many years. AMP is not the be-all and end-all blocker. It works very well but you need relatively high concentrations and it doesn’t work with everything. The next generation will use a lot of what’s going on in the world of molecular biology right now, and we’ll be able to direct the blocker right towards the receptor.
FTS: What are some of the breakthroughs that are occurring right now in your field?
Gravina: Recently, several additional proteins and receptors were identified by a group of researchers associated with Senomyx, Inc., which is our major competitor. But theirs is not a G.R.A.S. compound, so it may well take them ten years and $100 million just to come up with the product. We’re going to have AMP, if everything goes well, next year.
FTS: How is this new biochemical assay approach changing the way “artificial flavors” are produced?
Gravina: Understanding the biochemical pathways is the key. Once you understand what the receptors are, what the G proteins like gustducin are and what the affector enzymes are, you can mimic them in a test and screen large libraries of chemicals to find which ones tickle those receptors just right. And from those large libraries you’ll find all these new compounds. A typical library can be a million compounds, and nobody knows what’s in those compounds. You can’t have some poor flavorist sit and taste them all day, but I have a robot in my lab right now that can screen 1 million in a year.
“I have a robot in my lab right now that can screen 1 million compounds in a year.”
FTS: So then let’s say you wanted to screen the smell of onion...you’d find out which receptors were stimulated by the scent of onion and then in turn plug that in and run through your robot all the various potential odors that would lock onto those receptors and block the onion smell?
Gravina: That is correct. And now the revolution in molecular biology will move forward at an even faster pace because all the genes have been identified. So now we can find, for example, all the olfactory receptors in the human genome and pull them out of the gene, express them in some sort of a system and use them in a biochemical assay. It allows you to test smells or flavors or flavor blockers utilizing the biochemical reaction.
FTS: What do you foresee for the future of your industry?
Gravina: For Linguagen Corp., I see an explosion of activity. Previously, we’d experienced some resistance from the investment community because it’s very difficult for them to understand what this technology brings to them. But with all the coverage we’ve gotten, and the great interest in the human genome project, we’ve finally seen investors coming to our door. Researchers are talking to us; companies are talking to us; we’re getting new contracts; it’s very exciting.
FTS: And for the field as a whole?
Gravina: I think everyone in the field is very excited. I’m a protein biochemist so I work with the proteins—for which the human genome project has given us all the tools. So now it’s just a matter of me rolling up my sleeves and getting to work. There are untold numbers of discoveries to be made. So basic science-wise, it’s a great time to be in the field of flavor.