📋 Case Study
Bioethanol Fermentation Bioreactor Scale-Up with Inhibition Kinetics
Ethanol inhibition caused premature cessation at large scale despite matching nominal conditions
🏗️ Project Overview
Cellulosic ethanol pilot plant (10 m³) transitioning to commercial scale (500 m³)
🎯 Challenge
Ethanol inhibition caused premature cessation at large scale despite matching nominal conditions
🔧 Design Approach
Modified Monod model incorporating non-competitive ethanol inhibition (Ki = 75 g/L); CFD-guided impeller selection to minimize local ethanol hotspots
📐 Design Diagram
AI-generated project design illustration
📐 Key Calculations
Inhibition Constant (Ki)
μ = μ_max * S/(K_s+S) * 1/(1+P/K_i)
Result: 72.4 g/L
Calibrated from batch fermentations at varying [EtOH]
Local Ethanol Gradient
ΔP_local ≈ (Q_v * P_bulk) / (k_La * V_L)
Result: 18.6 g/L peak deviation
Explained localized cell death
Volumetric Productivity
Q_p = P_final / (t_ferment * V_reactor)
Result: 1.42 g/L·h (pilot), 0.91 g/L·h (commercial)
Quantified scale effect before mitigation
📊 Results
Final ethanol titer increased from 42 to 48 g/L, productivity restored to 1.35 g/L·h, reduced yeast inoculum requirement by 30%💡 Lessons Learned
- •Bulk-phase measurements mask critical microenvironmental gradients
- •Inhibition constants shift with strain adaptation—require periodic revalidation
- •CFD-coupled kinetic models outperform empirical correlations for bioreactor scale-up
✅ Key Takeaways
- 1Bulk-phase measurements mask critical microenvironmental gradients
- 2Inhibition constants shift with strain adaptation—require periodic revalidation
- 3CFD-coupled kinetic models outperform empirical correlations for bioreactor scale-up