How to Remove Microplastics from Water Using Yeast

Yeast acts as a natural biological sticky agent. When shaken with water, yeast cells attach to floating microplastic particles, forming heavy clumps called flocs. These heavy flocs sink to the bottom, making it easy to filter out clean water.

Medium ⏱ 90 min 🔭 Class 6-8 🏠 7 of 8 things are at home

Time: 90 min
Difficulty: Medium
Best for: Class 6-8
Subject: Chemistry
Things needed: 8, 7 at home
Steps: 14
Cost: Low, a few things to find
You will learn: Separation Methods and Bio-Aggregation

How to Remove Microplastics from Water Using Yeast, Experiment · Class 6-8 | jijnas.com

Before you start

What you need

0 of 8 ready

Tap each thing once you have it in front of you. Items with the house sign are already somewhere in your home.

🏠 Small transparent glass jars with tight lids (jam jars or small mason jars, approx. 250 mL capacity) 4 jars No luck? Use clear plastic jars or glass bottles with screw caps.
Fine craft plastic glitter (floating PET glitter) 12-15 g No luck? Use fine plastic glitter from a stationery or craft shop.
🏠 Baker's active dry yeast 1 small packet (approx. 10 g) No luck? Use instant yeast from a local grocery or bakery section.
🏠 Digital kitchen scale (0.1 g precision) 1 unit No luck? Use school lab balance or precise measuring spoon set.
🏠 Graduated cylinder or liquid measuring cup 1 unit (100 mL or 200 mL capacity) No luck? Use standard measuring cup or marked baby bottle.
🏠 Paper coffee filters or thin cotton handkerchiefs 4 pieces No luck? Use fine white cotton cloth (mulmul).
🏠 Small kitchen mesh strainer 1 unit No luck? Use tea strainer.
🏠 Large bowl or basin 1 unit

💬 Send to a parent

Think first

What do you think will happen?

Real scientists guess before they look. Write one line now. After the steps, the page will show it next to what you should see.

Do it

The procedure

Tap a step when it is done. Lab mode shows one step at a time in big letters, reads it aloud if you want, and keeps the timer.

Weigh out 3 grams of plastic glitter on your digital scale and place it into each of the four clean glass jars.
Add 0.5 grams of active dry yeast to the second jar, 1.0 gram to the third jar, and 2.0 grams to the fourth jar, leaving the first jar yeast-free as your control.
Measure and pour 200 mL of tap water into each jar.
Screw the lids tightly onto all four jars to prevent any fluid from leaking.
Shake each jar hard for two full minutes to mix the yeast and glitter thoroughly.Hold the lids firmly while shaking to prevent accidental spills or leaks.
Continue shaking each jar at a slower, gentle pace for five more minutes.
Note the starting appearance of the liquid and floating glitter in each jar, comparing the control jar to those with yeast.
Place all four jars on a flat, motionless surface and leave them untouched for 60 minutes.Do not bump or move the jars during the settling period, as motion will disrupt the clumps forming inside.
Examine the jars after one hour and record where the yeast and glitter have gathered in each container.
Position a paper coffee filter inside a small mesh strainer resting over a large basin.
Slowly decant the upper liquid layer from one jar through the filter, stopping before any sunken glitter at the bottom pours out.
Filter the floating liquid from the remaining three jars using a fresh coffee filter for each.
Leave all four coffee filters in a warm area until they dry completely.
Weigh each dry coffee filter on your digital scale to determine how much floating glitter was collected.

01 · The idea

The Concept

Microplastics are tiny pieces of plastic that float in water and pass right through basic strainers. In this demonstration, you use baker's yeast to trap these small plastic bits into heavier clumps that settle quickly, showing how living cells can help clean polluted water.

02 · What you should see

Observation

In the control jar without yeast, the plastic glitter remains floating undisturbed on top of the water. In the jars containing yeast, the glitter begins to group together and gradually sinks during the 60 minute resting period.

As you increase the amount of yeast from 0.5 grams to 2.0 grams, more glitter clumps together and settles at the bottom of the jar, leaving the water above it much clearer. When filtered through a coffee filter, jars with higher yeast concentrations leave far less floating glitter behind.

03 · Why it happens

Why It Happens

Microplastics float because they are light and water-repellent. When you shake the mixture, sticky surface proteins on the yeast cells lock onto the floating plastic glitter. Instead of single tiny plastic pieces, you get large, heavy bundles of yeast and plastic bound together.

Think of it like sticking heavy modeling clay all around a light ping-pong ball. On its own, the ping-pong ball floats on water, but once you weigh it down with enough heavy clay, the whole group sinks right to the bottom!

04 · The science

The Science Behind It

In standard water purification, we rely on methods of separation like sedimentation, decantation, and filtration. However, tiny microplastics are often too light to settle on their own and too small for basic filters to catch easily.

Baker's yeast (Saccharomyces cerevisiae) works through a process called bio-aggregation or flocculation. Yeast acts as a natural flocculant, binding suspended micro-particles into larger masses called flocs. Because these flocs are much denser than water, gravity pulls them down in a process called sedimentation.

Once all the plastic flocs sink to the bottom, the clean water on top can easily be poured off (decanted) or strained through a filter. Using living cells like yeast to clean up environmental pollutants is a modern scientific method known as bioremediation.

05 · Take it further

Make It a Project

Turn this classroom demonstration into a science fair experiment by measuring the mass of captured floating microplastics across different yeast concentrations:

Independent Variable: Amount of yeast added (0.0 g, 0.5 g, 1.0 g, and 2.0 g).
Dependent Variable: Mass of remaining floating glitter collected on the filter after drying.
Control Variables: Water volume (200 mL), initial mass of glitter (3.0 g), shaking duration, and settling time (60 minutes).

Data to Record: Record the initial mass of glitter, the mass of yeast added, the dry weight of each coffee filter before and after filtering, and calculate the overall percentage of microplastics removed.

Harder Follow-Up Question: How do variations in water pH or salt content affect the surface charges of yeast cells, and how does this change their ability to clump together different types of plastic like polystyrene or PET?

06 · Questions students ask

FAQs

Why does yeast stick to plastic particles?

Yeast cell walls contain natural sticky proteins and sugar molecules called beta-glucans. These outer structures easily lock onto synthetic plastic surfaces when you shake them together, binding the plastic to the yeast.

Does the yeast need to be alive for this to work?

No, the yeast does not need to be active or alive. The binding action happens because of the physical structure and sticky proteins on the outer cell wall, which remain effective even in dead yeast cells.

What is the difference between flocculation and sedimentation?

Flocculation is the step where small suspended particles clump together to form larger masses called flocs. Sedimentation is what happens next, when gravity pulls those heavy clumps down to the bottom of the liquid.

Can yeast remove all types of microplastics?

Yeast works best on floating microplastics like polyethylene and polypropylene. While it binds well to many common plastics, the exact pickup rate depends on the plastic type, shape, and surface roughness.

Why can't we just filter the microplastics without yeast?

Microplastic particles are often too light to settle and too microscopic for standard filters to trap. Yeast clumps them into larger, heavier bundles so basic household coffee filters can easily catch them.

Write it up

Your lab notebook

Two minutes here and your lab record is done. Everything stays on this device until you copy it out.

Did it work?

What I actually saw What I would change next time

💼 Same science, as a real job

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