Science Buddies: "Ask an Expert"

I'm already nearly done conducting my experiment, as my project is due within a week.

I've grown sweet potato plants with different amounts of potassium (in solution form),
so I'm testing the efficiency of the amylase breakdown. The results will most likely be
close, so I need a super accurate way to test efficiency. The last time I dealt with something
like this (in Biology class), the way we measured the enzyme reaction was really broad
and inaccurate. Basically, we just observed how "large" the reaction was and generated
quantitative data from that. So, that's what I'm not looking for.

How would I measure the efficiency of the breakdown? At the moment, I just have the potato plants
with the leaves and roots and definitely not the actual tuber.

I was wondering if I could cut off the leaves of the potato plant and "soak" them in the amylase.
Then in a given time frame, I could test the leftover solution for maltose after the breakdown.
Would this be plausible, or would it be better to test another part of the plant (ex: the roots, stem)?
And if I could test the maltose, how would it be done?

Am I missing something, or is there a more accurate way to test the breakdown by having quantitative data?
I have researched the ways of measuring the breakdown, but either the scientific papers are way over my head (I'm just a freshman)
or the majority of the papers simply discuss what happens after the breakdown.

Thanks,
mogmelon

Hi mogmelon,

I'm not sure exactly what you're trying to do? It sounds to me like you want to test amylase activity. Do you have access to a spectrophotometer?--here's a protocol that uses a spec to quantify the color change of the iodine, which will give you some numbers to put on your results: https://www.colby.edu/academics_cs/cour ... -assay.pdf

If you are interested in the levels of starch in the plants, I think the tubers is where the majority of starch is (and what's most relevant for people who eat the tubers, not the leaves!). So you should probably test the roots. I think you would want to grind or mash it up rather than just using a slice.

OK, if this isn't the kind of thing you're looking for, maybe post some more info about the question and experiment you're trying to do and maybe I can provide better advice. Or maybe another expert knows more about amylase breakdown than me?

good luck

Thank you for the quick reply.
I suppose it would make the most sense to test the roots and to mash them to get all the possible starch out.

I want to test the efficiency of the amylase breakdown. In some vague way, I'm trying to make my project relevant
to the biofuel industry. Researchers found that sweet potatoes can yield 2 to 3 times more carbs for fuel production
than corn does. So, they're dealing with costs of the sweet potato fuel production. Breaking down the starches
into maltose is a first step into fermenting the sugars for fuel production. I wanted to see how changing "environmental"
factors would influence the effiency of amylase breakdown. This way, the farmers or whoever cultivates the sweet potatoes
would have some kind of idea of what amount of nutrients to grow their potatoes with to help...

I think I'm somewhat on the right track. So my question would be, "How do different amounts of potassium (in form of potash)
affect the efficiency of the breakdown of starches in the sweet potato root?" And I'm using potassium in the form of greensand
which only has 6% total potassium...but it's the closest I could get to potassium itself, I'm sure with my resources (another question: is it possible to get purer forms of potassium?). So then I'm using
20% (of greensand which has 6% potassium), and 50%, 70%, and 90% potassium solutions. If I get a graph, I could have a trend either going up, down,
or in the shape of a bell curve, which will show people the general direction they should go in using potassium (fertilizer, I guess).

So after 5 days of using the potassium on the plants, then I will be ready to test for the amylase breakdown. And I was thinking about letting all of
the starch from the different plant roots sit in the amylase, and after a set time, I will test the "broken down" solution for leftover starches.
How much does a spectrophotmeter cost? It sounds really great if I could use because it may be just what I'm looking for.

Even though I got a lot of help with finding quantitative data, does anybody know other methods of measuring efficiency of amylase breakdown
(in terms of how much starch is leftover and how much of the other stuff got converted into sugar?) And other ways to extract the starch from the
potato plant? Thank you...

I think you are on the right track too--you have an interesting, and environmentally topical, question and it sounds like you've done a bit of research to back it up.

A spectrophotometer is a fairly serious piece of equipment--you wouldn't want to buy one for just a single experiment. If your high school labs don't have one, perhaps you could use one in a college research or teaching lab?

Here's a protocol I found for extracting starch; it looks pretty simple: http://www.rsc.org/education/teachers/l ... /3.1.7.pdf

I think you'll actually be testing two things--Does the varying potassium result in more/less starch? and Does the potassium make it easier/harder to turn that starch into sugar using amylase? You'll need to know what you started with in order to know if your reaction is more efficient at the end. And what if the roots are different sizes--you'll want to control for that by always starting with the same amount of material.

I post on the Expert Forum and see if anyone else knows more about starch chemistry than me.

amber

About knowing what I started with in order to know if the reaction is more efficient at the end,
I have a control group. So on those two plants I didn't use any potassium.
However, I feel much more relieved now about the way things are going.

Good, I'm glad it's going well for you.

What I meant is--if you want to measure efficiency, you'll need to get a ratio--how much starch there was in the roots versus how much your reaction gets out. Maybe the varying potassium will mean different amounts of starch in the roots, so you can't assume your starting material is the same.

I've already asked this question (how to extract starch from a sweet potato root), but I need more information sources.
I only have a small root on my plants and the site I was pointed to only told how to make a starch solution from a whole potato.
I may not even have a tuber on my plants, so I need serious help.

I've already e-mailed my chemistry teacher, but does anyone here know a way to extract starch from thin potato roots?
I could just use the whole plant if there's no other way to do it, but I need more information.

I would guess you can just scale down the volume of the protocol? As long as you have control roots to compare your conditions to, it should be ok.

Ideally in this situation you would start out by doing a "pilot" experiment--just a couple roots to test your protocol and make sure it works properly--before going on to the actual experiment. I don't know if time and your plants would allow for this. Maybe you can go to the grocery store and try to find something with skinny roots like you're anticipating, and try to develop a starch extraction protocol with that plant tissue?

Starch does come out pretty easily--I was making potato latkes the other day and when I squeezed the moisture out of the shredded potatoes, all the starch settled on the bottom of the bowl.

Hi!
If you google: "Extract starch potato" you should get some pretty good links. Here's one which gives a simple protocol for extracting the starch-
http://www.rsc.org/education/teachers/l ... /3.1.7.pdf
Hope this helps, good luck!