Kefir Whey Bioplastic Optimization Project

ISEF Category: Microbiology

Subcategory: Applied Microbiology  ·  Difficulty: Advanced  ·  Setup: University Lab  ·  Time: Full Year

The Hook

Plastic is everywhere, and most of it sticks around for a very long time. Your project asks a smart question, can bacteria turn dairy waste into a usable bioplastic instead? You get biology, chemistry, and materials testing in one project. That makes this topic strong for a science fair, if you plan it carefully.

What Is It?

This project studies polyhydroxyalkanoates, or PHAs. PHAs are bioplastics that many bacteria store inside their cells as energy reserves, kind of like tiny battery packs. If you feed the right bacteria the right carbon source, they can build these plastic granules instead of just growing more cells.

Kefir whey is the liquid left after dairy fermentation. It still contains sugars and nutrients, so it can act as a low-cost feedstock. Glycerol can also give the bacteria extra carbon. Your job is to test how changing the recipe affects PHA-like granule production, then see whether the material has enough strength to matter as a plastic.

Nile-blue-A is a dye that can stain PHA granules so you can estimate how much polymer the cells made. A tensile rig measures how much force a sample can take before it stretches or snaps. Together, these tools let you connect microbiology to material performance.

Why This Is a Good Topic

This is a strong science fair topic because you can vary real process inputs and measure real outputs. You can test feedstock ratio, carbon source, and growth conditions, then connect those choices to granule yield and film strength. The project also connects to food waste reuse and sustainable materials, which gives your work a real-world angle. A student can learn experimental design, staining, image analysis, and basic mechanics from one project.

Research Questions

• How does the whey to glycerol ratio affect PHA-like granule accumulation in B. subtilis??
• What is the effect of carbon source concentration on Nile-blue-A staining intensity in bacterial cells??
• Does changing the nitrogen level alter the amount of polymer stored per cell??
• To what extent does the starting pH of the growth medium change final bioplastic yield??
• Which medium formulation produces the strongest dried film in a DIY tensile test??
• What is the effect of incubation condition changes on granule size distribution and film brittleness??

Basic Materials

• Lab-safe Bacillus subtilis strain.
• Sterile kefir whey or clarified whey filtrate.
• Glycerol, preferably reagent grade.
• Nile-blue-A stain.
• Petri dishes or sterile culture tubes.
• Basic sterile pipettes and tips.
• Incubator or temperature-controlled growth space.
• Light microscope or fluorescence-capable microscope.
• Microscope slides and coverslips.
• Digital balance with milligram readability.
• Camera or phone mounted on a tripod for consistent imaging.
• Ruler or calipers for sample measurements.
• Simple film-casting molds or flat drying surfaces.
• DIY tensile rig materials such as clamps, weights, and a force gauge or spring scale.

Advanced Materials

• University-approved PHA-positive and PHA-negative control strains.
• Autoclave and biosafety-approved sterile workspace.
• Fluorescence microscope with filter set matched to Nile-blue-A.
• Spectrophotometer or plate reader for growth and stain quantification.
• Centrifuge for pellet collection and sample cleanup.
• Solvent-resistant casting plates for polymer recovery and film formation.
• Texture analyzer or universal testing machine for tensile measurements.
• Differential scanning calorimetry for thermal properties.
• FTIR instrument for functional group analysis.
• Scanning electron microscope for granule or film surface imaging.

Software & Tools

• Google Sheets: Organizes factor levels, response values, and simple plots for your optimization matrix.
• Python: Helps you fit a response-surface model and compare factors with statistics.
• ImageJ: Measures fluorescence signal, granule area, and film thickness from microscope images.
• R: Runs regression, ANOVA, and interaction plots for your experimental design.
• GraphPad Prism: Makes clean dose-response and comparison graphs if your school or lab has access.

Experiment Steps

1. Define the exact response you will optimize, such as granule signal, polymer yield, or film strength.
2. Choose your independent variables and keep the list small enough for a real design matrix.
3. Plan a control group that separates growth effects from polymer production effects.
4. Build a standard way to score the stain signal, so every sample gets measured the same way.
5. Select a response-surface design that lets you test interactions, not just one factor at a time.
6. Plan a materials test that matches your biology result, so you can connect yield to strength.

Common Pitfalls

• Using a stain signal as if it were pure polymer mass, which can overstate yield if cell density changes.
• Comparing samples grown in different light or camera settings, which makes fluorescence measurements drift.
• Testing film strength before samples dry to the same thickness, which hides real differences in material quality.
• Changing more than one medium factor at once without a design matrix, which makes the cause of each result unclear.
• Ignoring a non-PHA control strain, which makes it hard to tell whether the stain reflects true granules or background signal.

What Makes This Competitive

A strong version of this project does more than compare a few recipes. You build a real experimental design, measure both biological output and material performance, and test whether the two actually track together. You can also strengthen the work by including controls, replicates, and a model that predicts the best formulation. That turns a simple growth study into a systems-style project with cleaner logic and better data.

Project Variations

• Test whey from different dairy sources, such as kefir, yogurt whey, or cheese whey, and compare which one supports the best polymer signal.
• Replace the film-strength test with thermal analysis or water-uptake testing to study whether your bioplastic behaves more like a packaging material or a brittle gel.
• Compare Nile-blue-A staining results with an alternative readout, such as dry mass recovery or image-based granule counting, to check how well the stain predicts yield.

Learn More

• USDA National Agricultural Library: Search for review articles on whey valorization, bioplastics, and dairy byproduct reuse.
• NIH PubMed: Search for reviews on polyhydroxyalkanoates, Nile-blue-A staining, and microbial biopolymer production.
• PubChem: Look up Nile blue A, glycerol, and related compounds for basic chemical properties and safety summaries.
• NCBI Bookshelf: Search for free textbook chapters on bacterial metabolism and polymer storage granules.
• MIT OpenCourseWare: Search for materials science or bioprocess engineering lectures on polymer processing and experimental design.
• Applied and Environmental Microbiology: Search the journal for PHA production, carbon source optimization, and bacterial biopolymer studies.