Scientist of the Year Awards 

David Johnston, "Outstanding Early Career Research Scientist", interviewed 2006

I'm David Johnston. I'm a lead scientist and research food technologist. I'm being recognized for developing new ways of processing corn that eliminate a hazardous processing agent, sulfur dioxide,  and replacing that with environmentally friendly enzymes.

For me it's a very big honor to be awarded this title. It's nice to be acknowledged for the work that I have been doing. I take great pride in the work that I do.

We started with a very small idea and it really snowballed into something much bigger. 

Wet milling is the process in which the corn kernel is fractionated into a range of components--
corn starch, germ which is eventually processed to make corn oil, corn gluten meal which is the high protein co-product used for feed, and corn gluten feed which is a high fiber feed mainly for ruminants. 

What the conventional process with the sulfur dioxide, the sulfur dioxide slowly penetrates into the intact kernel and disrupts the protein/starch interactions. With the enzymes they're actually too large to penetrate the corn kernel but by doing a short water soak, to hydrate the kernel, we can then do a course grinding basically open up the whole corn kernel so that the enzymes can get in and do their job which was to break the protein/starch interactions.

There had been some previous research on the addition of enzymes and it showed some positive results and so we started out seeing if we could identify specifically what enzymes were involved. So we designed experiments around that only to find out that we really couldn't see what other people have reported and we started investigating, you know, why that was.

It was a fairly small discovery that the enzymes couldn't penetrate the intact corn kernel that led us to start trying new things. The other thing is, is that the sulfur dioxide which is the chemical treatment component in wet milling interfered with all the enzymes assays that I was trying. 

So I said well let's eliminate that to see what happens and that was when everything started and we realized that by eliminating it we could actually see the effects of the enzymes. We were able then to identify specifically what enzyme was giving a beneficial effect and start to investigate more about those particular enzymes, mainly proteases.  

Sulfur dioxide has a couple of bad things about it. One it's fairly volatile, it makes smelly compounds. It also has some health hazards associated with it and some regulatory things. Once it goes up into the air, it can help contribute to acid rain.

 I'd like to think that the work that I've been doing will have a number of effects--one it will help clean up the area in which the wet milling facilities are. It'll also benefit consumers because they won't have those residual sulfur dioxide levels and co-products. 

Originally our work set out to develop a process for wet milling but we quickly realized that we could pull out new co-products for the ethanol process. Those then could go on to make feeds or the process for making corn oil which would be value-added components for the ethanol industry. 

Also in the wet milling process, the use of sulfur dioxide basically eliminates all of the products from that process from being considered organic. With the enzymatic process we could completely eliminate the use of sulfur dioxide in the process so that all of those co-products would be considered organic. 

Right now in the food industry, there is a large demand for organic feeds to produce organic animals and so on. So, by using this process you could potentially produce a great volume of feed that could go on to produce organic animals.

Some of the analysis that we do in the laboratory is looking at nutritional quality of materials and looking at amino acid profiling is something that I do quite a bit, particularly with the ethanol  processing.

There's a big emphasis on feed value for the co-products from the ethanol industry mainly because the industry is growing so quickly there's a lot of material available. So, what is it good for is something that we're really looking at and we're looking at ways of altering the nutritional value of the material. That material is basically cattle feed but I'm looking at ways of can I change that nutritional profile so that it would be more valuable for other animals.

Corn is deficient in a number of amino acids and I'm looking at ways of altering that to improving the amino acid profile.  

Agricultural research is expensive and to do big projects is difficult and ARS really supports agriculture in a big way by supporting the research that we do here.

I like the people that I work with a great deal. I like that there's flexibility and I see it as being very important because right now in industry a lot of the emphasis has gone away from research so that we're doing research that wouldn't be done otherwise and we're developing new processes, new co-products and things that would not be done in industry. In the long run what will happen is those beginnings of research will stir industry to be able to do new things that they weren't able to do and I guess that's what being Scientist of the Year means to me.