Enter fermentation or culture data
Use the responsive calculator grid below. It shows three columns on large screens, two on smaller screens, and one on mobile.
Example data table
This example uses glucose as substrate and lactate as product.
| Example item | Value | Unit |
|---|---|---|
| Initial biomass X1 | 1.0 | g/L |
| Final biomass X2 | 2.2 | g/L |
| Initial substrate S1 | 20.0 | g/L |
| Final substrate S2 | 12.0 | g/L |
| Initial product P1 | 0.5 | g/L |
| Final product P2 | 2.9 | g/L |
| Time interval | 8.0 | h |
| Specific growth rate | 0.0985 | 1/h |
| Specific substrate uptake qS | 0.6250 | g/g/h |
| Specific product formation qP | 0.1875 | g/g/h |
| Biomass yield Yx/s | 0.1500 | g/g |
| Product yield Yp/s | 0.3000 | g/g |
Formula used
Core balances
Biomass change: ΔX = X2 − X1
Substrate consumed: ΔS = S1 − S2
Product change: ΔP = P2 − P1
Specific rates
Average biomass: Xavg = (X1 + X2) / 2
Specific growth rate: μ = ln(X2 / X1) / Δt
Specific substrate uptake: qS = ΔS / (Xavg × Δt)
Specific product formation: qP = ΔP / (Xavg × Δt)
Yield terms
Biomass yield: Yx/s = ΔX / ΔS
Product yield: Yp/s = ΔP / ΔS
Pathway split estimates
Normalized pathway split = entered split / total entered split
Glycolysis flux: qS × glycolysis share
PPP flux: qS × pentose phosphate share
TCA flux: qS × TCA share
Carbon recovery
Substrate carbon consumed: ((ΔS × volume) / MWsubstrate) × Csubstrate
Product carbon captured: ((ΔP × volume) / MWproduct) × Cproduct
Biomass carbon captured: (ΔX × volume) × biomass carbon factor
Total carbon recovery: ((product carbon + biomass carbon) / substrate carbon) × 100
How to use this calculator
- Enter biomass concentrations at the start and end.
- Enter substrate concentrations before and after the interval.
- Enter product concentrations for the same interval.
- Set the elapsed time and reactor volume.
- Provide molecular weights and carbon numbers for substrate and product.
- Enter a biomass carbon factor from your organism model or literature.
- Add pathway split percentages for glycolysis, PPP, and TCA.
- Press the calculate button to view results above the form.
- Review the graph, exports, yields, and carbon recovery metrics.
- Use the notes section to spot weak assumptions or data inconsistencies.
Frequently asked questions
1. What does this calculator estimate?
It estimates growth rate, substrate uptake, product formation, yields, pathway split fluxes, and carbon recovery from steady-state interval data.
2. Is this a full isotopomer MFA solver?
No. It is a practical screening calculator. It uses concentration changes and pathway split assumptions rather than isotopic labeling matrices.
3. Why is average biomass used in qS and qP?
Specific rates should be normalized by biomass present during the interval. Average biomass is a simple and common approximation.
4. Why are pathway percentages normalized automatically?
Users often enter splits that do not sum exactly to 100. Normalization preserves the relative distribution and prevents invalid flux totals.
5. What does low carbon recovery imply?
Low recovery can indicate missing byproducts, CO2 losses, evaporation, measurement noise, or an incorrect biomass carbon factor.
6. Can I use other substrates and products?
Yes. Replace molecular weights and carbon numbers with values for your chosen compounds. The equations update automatically.
7. What units should I use?
Use g/L for concentrations, hours for time, liters for volume, g/mol for molecular weight, and C-mol/g for biomass carbon factor.
8. When should I avoid these results?
Avoid direct interpretation when cultures are highly dynamic, substrate increases over time, or pathway split assumptions are unsupported.