Rate depends on temperature (optimal ~30–35 °C for
Saccharomyces cerevisiae), sugar availability and yeast
population. Above 40 °C enzymes denature; below 10 °C metabolism slows
drastically.
About the Fermentation Simulator
This simulation models alcoholic fermentation by brewer's yeast (Saccharomyces cerevisiae) converting sugar into ethanol and carbon dioxide, following the Gay-Lussac equation C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂. Yeast growth uses logistic kinetics with a Monod term for sugar uptake (half-saturation constant Ks = 20 g/L), while temperature scales the rate via a Gaussian factor peaking near 32 °C. Ethanol product inhibition slows activity as concentration approaches 14% v/v.
The sliders set temperature (0–50 °C), starting sugar concentration (10–300 g/L) and yeast inoculation (1–20 g/L), and preset buttons load realistic Beer, Wine, Bread and Optimal recipes. As you watch, CO₂ bubbles rise through the flask, yeast cells bud, and live graphs track falling sugar against rising ethanol, CO₂ and dropping pH. Fermentation underpins brewing, winemaking, baking and biofuel production worldwide.
Frequently Asked Questions
What does this fermentation simulator actually show?
It shows yeast cells consuming sugar in a sealed flask and producing ethanol and carbon dioxide over time. You see the cells move and bud, CO₂ bubbles rise, the liquid turn amber, and live readouts of sugar (g/L), ethanol (% v/v), CO₂ (g/L) and the growth phase.
What is the chemical reaction behind fermentation?
Alcoholic fermentation follows the overall Gay-Lussac equation C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂, plus a net 2 ATP that powers the yeast. One glucose molecule yields two ethanol molecules and two carbon dioxide molecules, which is why every gram of sugar produces both alcohol and gas.
How do the temperature, sugar and yeast sliders change the outcome?
Temperature scales the reaction rate, peaking around 32 °C and collapsing above 45 °C as enzymes denature. Higher starting sugar gives a higher potential alcohol level, and more yeast shortens the lag phase and speeds the early ferment. Together they control how fast and how completely the sugar is converted.
What do the Beer, Wine, Bread and Optimal presets do?
Each preset loads a realistic recipe: Beer uses 18 °C, 120 g/L sugar and moderate yeast; Wine uses a cooler 15 °C with a high 200 g/L sugar; Bread uses a warm 35 °C with low sugar and heavy yeast for fast gas; and Optimal sets 30 °C, 150 g/L and 8 g/L yeast for the most efficient ferment.
What does the growth-phase indicator mean?
Yeast populations move through four classic stages: Lag (cells adapting), Exponential (rapid budding and sugar consumption), Stationary (growth balanced by limits), and Decline (sugar exhausted or ethanol too high). The bar highlights the current stage based on elapsed time and how much sugar remains.
Why does the pH drop as fermentation proceeds?
Dissolved CO₂ forms carbonic acid and yeast also release organic acids, so the medium becomes more acidic. In the model pH falls from about 6.5 toward roughly 3.5 as CO₂ accumulates. This mild acidification is real and helps protect ferments from spoilage microbes.
Why does fermentation stop before all the sugar is gone?
Ethanol is toxic to yeast, so as it climbs the cells slow down and eventually stall. The simulation caps ethanol near 14% v/v, the typical tolerance limit for wine strains. At low temperatures metabolism also slows so much that fermentation may stop with residual sugar remaining.
Is the kinetic model physically accurate?
It captures the right qualitative behaviour using Monod sugar uptake, logistic yeast growth, an Arrhenius-style temperature factor and ethanol inhibition, with realistic yields of about 0.51 g ethanol per gram of sugar. It is a teaching model, however, and simplifies pH, nutrients and strain differences, so it should not be used for precise commercial brewing predictions.
Why does the liquid turn amber as it ferments?
The visual colour shift is a stylised cue linked to rising ethanol concentration, suggesting the developing body and warmth of a maturing beer or wine. In real fermentation, colour comes mainly from the grains, fruit or malt rather than ethanol, but the cue helps you see progress at a glance.
What real-world uses does fermentation have?
The same biochemistry drives brewing beer, making wine and cider, leavening bread, and producing spirits, kombucha and many fermented foods. Industrially it also yields bioethanol fuel and feedstock chemicals. Understanding how temperature, sugar and yeast interact is central to controlling flavour, alcohol strength and speed in all of these processes.