Moringa seed coating can kill bacteria, viruses, and fungi

Purifying water with proteins made by seeds
13 April 2021

Interview with 

Manish Kumar, The University of Texas at Austin




Seeds are robust because they have tough outer casings to protect the delicate embryo inside, but they can still fall foul to attack from microbes that can “break in”. These thrive in damp places like the soil, so many seeds have evolved special antimicrobial coatings to repel the threat. So could we take a leaf out of the seed’s book and use these chemicals to purify water? Manish Kumar thinks so, he’s at the University of Texas at Austin, and spoke with Eva Higginbotham...

Manish - So these coatings are essentially seed storage proteins, they call them. And it's very interesting that they're called that, because it helps the seed survive attack from microbes. And the way it does it is by having proteins that can penetrate the membrane of, say, bacteria, but not human cells. So they're safe to eat, but they'll puncture a hole or fuse the membranes of bacteria and kill them. So that's what's in this protective coating in these seeds.

Eva - And is this a coating that the seed itself has made, or is it a coating that its parent made and sort of covered it in?

Manish - That's a good question. I actually don't know. I think the cells that are present in the seed express this protein and then distribute it throughout the tissues to provide this antimicrobial function.

Eva - And does it work on just bacteria? What about viruses and fungi too?

Manish - Yeah, so this was new for us. We were working with a specific seed from the Moringa oleifera tree, and we found that this one protein in the seed was actually attaching to viruses. And then we figured out that this protein had domains that bind to fungi. So they do protect against fungi as well.

Eva - It sounds like sort of a miracle substance that can help protect us from all sorts of things! Is there a way that we could try and exploit that?

Manish - Yeah, so what we do in our lab - or what we've been trying to do - is to use it for water purification. So when you take these proteins and attach them to, say, sand, and you flow water through it, and if your water has lots of microbes, bacteria, and even viruses, now almost all of it gets removed as the water passes through it. And this is very surprising, because we use sand for water filtration in general, in all water treatment plants, and they don't remove any viruses. And this removes billions of viruses per mil. So that's one thing we are working on.

Eva - Have you actually done the experiment where you've taken, for example, some solution that has a known amount of a bacteria that we know causes illness in people, something like cholera; filtered that through with your seed protein; and then used what's come out, the filtered water, in an experiment to quantify how much bacteria was actually removed, and if you managed to remove enough to actually prevent infection in a person?

Manish - Yes. So we have done this with E. coli. If there are billions of cells per mil, you can remove all of it. We can't measure it anymore on the other side. We have removed virus solutions as well - different types, two or three different types. So we've done extensive studies on these, and it seems to be very effective.

Eva - Is it all seeds? Or is it just these Moringa seeds?

Manish - This is a very interesting question. So all the seeds that I've heard of have some antimicrobial properties. Specifically onion seeds, seeds from mustard, rapeseed - these are the ones that we know. These seeds have these cationic or charged antimicrobial peptides, they call them, that have very similar functions, but we have only gotten Moringa proteins to work on attached surfaces. So all of these have anti-microbial properties; people have shown different levels of anti-microbial activity; but when we put them on a surface and try to remove bacteria in a filtration type of setup, for us, only Moringa has worked. And we're trying to figure out why that is.

Eva - So if I had some of these Moringa seeds and I went camping or something, and I had some dirty water from a stream, could I just slap some of these seeds in, leave it for a bit, and then drink it?

Manish - Yes. So what you could do is you crush it with stone, and if you had a piece of cloth, you can dip your cloth in that water, and then you can make a little filter out of it. You pour water on one side - it has to go slowly - and the other side will have clean water. It's shocking! We've done this in the lab, we do it at demonstrations with bacteria that are coloured, and you can see clear water coming out on the other side. So it's very, very effective.

Eva - It sounds amazing, but I'm wondering how scalable this is. Would we need to have big farms and plantations growing all of these seeds? Where do you think in the world would using these seeds to clean water be most beneficial?

Manish - There are two ways we think about this. So in the developing world, there is a problem with purifying water because there are no filters that remove bacteria or viruses. And one of the ways to do this is chlorination, you can add bleach; but bleach is not easy to get in many parts of the world. So in the developing world, this could help as being a filter where you can pour water through and then drink it. So it'll be very effective there. In disaster situations - just like you said, you were going out camping - but say, for example, I'm in Texas, we lost clean water and electricity for five or six days in some places, and we had a boil water notice. Instead of boiling water you could use this, if you had an emergency kit with just some seeds. And the third case is big water plants - can you scale this? You could scale this, and what this will help you with - say, for example, if you retrofit a plant with sand containing these proteins on it, then you don't have to chlorinate the water afterwards to remove most of the microbes. What this does is it produces less disinfection by-products. These disinfection by-products are chemicals such as chloroform. So this could help us at many different levels.


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