Explore a different plant storage polymer
Compare a soluble inulin substrate with and without enzyme using a fructose-compatible or reducing-sugar assay. Glucose-specific strips are not a direct fructose readout.
Use these original S&T teaching drafts after a teacher or technician has piloted the exact product, substrate and assay. Recipes and timing targets are proposed starting conditions, not validated performance claims. Review current SDS and institutional guidance; wear eye protection, avoid enzyme aerosols and splashes, and keep powders under technician control. No tasting. Keep controls at the same final volume, pH, temperature and stirring conditions. Plan reagent-specific waste disposal.
Inulinase in nature
Inulin is a fructan used as a storage carbohydrate by some plants. Microorganisms can produce inulinases to access fructose-containing chains. Different inulinase activities can release fructose or shorter fructooligosaccharides.
What chemical reaction does it catalyse?
Enzymes speed up a reaction without being consumed in the overall process. The preparation, accessible substrate and reaction conditions determine what you can measure.
Industrial applications
Inulinases are used in fructose production and fructan processing. Enzyme specificity determines the product mixture.
Experiment overview
Compare a soluble inulin substrate with and without enzyme using a fructose-compatible or reducing-sugar assay. Glucose-specific strips are not a direct fructose readout.
Equipment and materials per working group
- 1% w/v soluble inulin near pH 5
- Technician-prepared 1% w/v inulinase stock
- Three tubes, pipettes, timer and 40°C bath
- School-approved reducing-sugar assay or fructose-specific assay and fructose standard
Plan a class of 30
Use 10 working groups of three. Multiply the per-group quantities in this guide by 10, then allow an appropriate preparation reserve. Keep concentrations unchanged when scaling. Assign a timer, a practical operator and a recorder, then rotate roles. Set up teacher-prepared comparison samples in advance where a reaction takes longer than the lesson.
Teacher and technician preparation
- Prepare inulin and enzyme stocks under technician control and confirm substrate solubility.
- Pilot 0.5 mL 1% enzyme stock with 4.5 mL substrate: 5 mg product in 5 mL final reaction.
- Check that the chosen assay responds to fructose; follow its approved reagent volumes and development conditions.
Use enough working enzyme to make a clear comparison in the intended time window. Do not automatically add more concentrate: reactions can finish before measurement, stocks can alter pH or background colour, and some substrates remain slow even at a high dose. Pilot the proposed recipe, then record the final preparation and dilution on the results sheet.
Step-by-step class method
- Label ENZYME, CONTROL and ENZYME BLANK.
- Add 4.5 mL inulin to the first two and 4.5 mL buffer to the blank.
- Equilibrate at 40°C for 3 minutes.
- Add 0.5 mL selected enzyme solution to ENZYME and the blank and 0.5 mL diluent to CONTROL.
- Collect equal samples at 0, 5 and 10 minutes.
- Develop the chosen assay identically for each sample and standard.
- Compare increases over both backgrounds.
- Discuss why an inulin reaction can produce sugar without producing a strong glucose-strip response.
What should students look for?
A compatible assay may show increased reducing sugar or fructose in the treated sample.
Interpretation and troubleshooting
Reaction and assay times must be stated separately. Powder stocks and heated or alkaline assay reagents require technician handling appropriate to the local procedure.
Questions for the class
- What changed in the enzyme-treated sample compared with the control?
- What bond or substrate does this enzyme act on?
- Which conditions did we keep the same, and why?
- Could colour, pH, warming, stirring or background sugars explain part of the result?
- What would you measure or change in a follow-up investigation?
Your investigation sheet
Name: ____________________ Group: ______ Date: __________
Prediction: _______________________________________________________
Enzyme preparation / batch: ________________________________________
Final working dilution and dose: ____________________________________
Substrate: _______________ pH: ______ Temperature: ______ °C
| Time / min | Enzyme + substrate | No-enzyme control | Enzyme-only blank / notes |
|---|---|---|---|
| 0 | ________________ | ________________ | ________________ |
| 2 | ________________ | ________________ | ________________ |
| 5 | ________________ | ________________ | ________________ |
| 10 | ________________ | ________________ | ________________ |
| Later: ___ | ________________ | ________________ | ________________ |
Conclusion supported by our control: _________________________________
One limitation and one improvement: __________________________________
Background sources and product details
This is an original teaching adaptation. External methods establish useful principles and assay formats; they do not validate the suggested doses for S&T preparations.