Purpose and Scope

This overview introduces the FermAxiom Yeast Propagation Simulator — a five-tool integrated suite for industrial-yeast propagation design and end-product performance prediction — and positions it within a three-tool family alongside the Specific Growth Rate Calculator and the Yeast Growth Kinetics Analysis.

The Yeast Propagation Simulator (Biomass Propagation Suite v3.0) provided below is an integrated five-tool environment for designing and projecting aerobic batch + fed-batch propagation of Saccharomyces cerevisiae under industrial conditions, then forecasting the application performance of the harvested biomass. Where the analytical tools in this family characterize a strain from data, the Simulator runs the design problem end-to-end: from a target dry-biomass production back to a complete media recipe and cultivation protocol, then forward into application-specific performance predictions for baker's yeast (CO₂ activity in dough), nutritional yeast and single-cell protein (crude protein, RNA, amino-acid quality), and shelf-stable dry-yeast products (viability decay over storage). The five tools share live state through a central event bus, so a change to nitrogen content in the medium recipe immediately updates the protein prediction, the dough activity curve, the storage shelf-life forecast, and the regime recommendations downstream. A sixth tab — Model Notes — documents the inter-tool data flow and the scientific basis of every kinetic model in the suite.

The Propagation Medium Composition Calculator is the authoritative source of biomass composition for the suite. The user specifies a target dry biomass split between batch and fed-batch phases, a final biomass concentration that sets the fermentor volume, an inoculum mass, and a stoichiometric yield Y_X/S; the calculator derives the demand for every macronutrient (C, N, P, K, Mg, S, Ca, Na), trace metal (Fe, Zn, Mn, Cu, Mo, Co), and vitamin (eight B-vitamins plus inositol) needed to support that biomass under aerobic respiratory metabolism. Three medium classes are supported — defined, semi-defined, and complex — with a live Medium Type badge auto-classifying the recipe by total g/L of complex materials. Five complex-material sources (yeast extract, peptone, corn steep liquor, cane molasses, beet molasses) can be dosed in any combination, and the calculator credits their nutrient delivery against the salt recipe in real time. A utilisation-efficiency correction inflates stoichiometric minimums by 10–40% to account for real-world losses, and a deficiency-analysis panel flags any nutrient still under-supplied. The output is a Procedure-ready weigh-out sheet with macro / trace / vitamin / process-additive sub-cards, batch-phase and fed-batch-feed splits, stock-solution recipes (10× / 100× / 40× / 20×), an 11-step cultivation protocol with live-computed values, and a per-compound media cost estimate.

Three application-side simulators read the biomass composition from the Medium Calculator and predict end-product performance. The High Protein module computes crude protein via Kjeldahl stoichiometry (N × 6.25), true protein after correcting for nucleic-acid nitrogen, RNA content (which must remain below the 2% FAO/WHO 1975 ceiling for human food-grade nutritional yeast), and amino-acid quality through a lysine index, with strain ceilings for S. cerevisiae (50%), C. utilis (55%), K. marxianus (45%), and Y. lipolytica (42%). The Activity Simulator projects 0–180-minute CO₂ evolution in dough fermentation across four application presets (lean, sweet, very sweet, frozen) using a six-factor modified-Monod model with osmotic inhibition, temperature Q₁₀, and maltose-lag dynamics; outputs are directly comparable to the rheofermentometer benchmarks used by industrial bakeries for QC. The Stability Optimizer projects viability decay during storage using first-order Arrhenius kinetics with five multiplicative factors — water activity, temperature, trehalose content (Crowe water-replacement), lipid composition, and headspace oxygen — across the four commercial yeast formats (cream, compressed, active dry, instant dry), each with its own baseline decay rate calibrated to industrial shelf-life specifications.

The Strain & Composition Designer runs the suite in reverse. Given a target application — baking style, product format, shelf-life requirement, certification constraint (organic / vegan / kosher / halal), and cost tier — the Designer's rule-based expert system emits a complete recommended propagation regime: biomass composition targets (N, P, K, Mg, trehalose, lipid), medium class, fed-batch strategy, N-limitation timing for trehalose accumulation, stationary-phase duration, dissolved-oxygen target, growth temperature, harvest pH, drying and packaging recipe, and recommended additives. A Push to Medium Calculator action applies the recommendations back to the Medium Calc input fields and re-runs every downstream simulation simultaneously, closing the design loop in one click. A decision-path panel explains why each rule fired and flags any application / format / certification conflicts before the user commits to the regime.

The Specific Growth Rate Calculator is the recommended starting point for kinetic-envelope analysis around the operating point this suite assumes. Where the Yeast Propagation Simulator runs at the regime level (target DCW, final concentration, harvest phase, application target), the Specific Growth Rate Calculator zooms into the kinetic envelope underneath: it returns the instantaneous μ for any combination of glucose, ethanol, temperature, and pH using a multiplicative factor decomposition with seven f(S), five g(P), five h(T), and two i(pH) sub-models, plus side-by-side strain comparison. Use the Specific Growth Rate Calculator to scope μ_max and the temperature / pH operating window before fixing the propagation regime in the Simulator.

The Yeast Growth Kinetics Analysis is the analytical companion that supplies the empirical parameters this suite consumes. From real fermentation data — biomass time-series with optional substrate and product concentrations — the Analysis tool extracts μ_max, doubling time, carrying capacity, lag time, exponential and stationary phase durations, and (when substrate or product data is also provided) the yield coefficients Y_X/S and Y_P/S that drive the Medium Calculator's stoichiometric calculations. Used together, the three tools form a complete yeast propagation workflow: extract parameters from data with the Analysis tool, scope kinetic sensitivity with the Specific Growth Rate Calculator, then design the full propagation regime, predict end-product performance, and project shelf life with the Yeast Propagation Simulator.