Select an organism to auto-fill typical OUR, kLa requirements, and gas strategy across all calculators below.
Gas Blend Calculator (O2 Enrichment)
Calculate the required inlet gas pO2 and O2/air blend to maintain target dissolved oxygen. Formula: pO2 = (OUR/kLa + CL) / C*_per_atm_O2
Target DO (% air sat.)
kLa (h-1)?
Cell OUR (mmol/L/h)?
Temperature (C)
Sparger Flow Rate Calculator
Calculate total gas flow rate from bioreactor volume and vvm. Split between ring sparger (bulk aeration) and point sparger (CO2/overlay).
Bioreactor Volume (L)
Target vvm ?
Ring Sparger Split (%)
Back Pressure (bar)
VVM Presets by Application
CHO (0.5)
CHO overlay (0.02)
E. coli (1.0)
Pichia (1.5)
High density (2.0)
CO2 / pH Control (Henderson-Hasselbalch)
Calculate required %CO2 in gas blend for pH control via bicarbonate buffer. pH = 6.1 + log([HCO3-] / (0.03 x pCO2))
Target pH
[HCO3-] (mM)?
Temperature (C)
Headspace Pressure (atm)
CO2 Stripping Effect from Sparging
Gas Flow (L/min)
Volume (L)
Current dCO2 (mmHg)
N2 Blending for Low DO (Microaerobic/Anaerobic)
Calculate N2/air blend for microaerobic fermentation. Target DO < 5% air saturation.
Target DO (% air sat.)
Total Gas Flow (L/min)
Cell OUR (mmol/L/h)
Oxygen Enrichment Strategy (Breakpoint Analysis)
At what cell density does air-only sparging become insufficient? Shows OUR demand vs kLa supply as VCD increases.
kLa (air) (h-1)
Specific OUR (mmol/109 cells/h)?
Max VCD (106/mL)
Temperature (C)
Gas Cost Estimator
Estimate total gas costs per batch based on flow rates and run duration.
Air Flow (L/min)
O2 Flow (L/min)
CO2 Flow (L/min)
N2 Flow (L/min)
Run Duration (hours)
Supply Type
Frequently Asked Questions
When is oxygen enrichment needed in a bioreactor?
Oxygen enrichment is needed when the oxygen uptake rate (OUR) of the culture exceeds the oxygen transfer capacity with air-only sparging. This occurs when OUR > kLa x C* (air saturation). At 37C, C* for air is approximately 0.21 mmol/L. High cell density E. coli (OUR 100-300 mmol/L/h) or Pichia pastoris (OUR 200-400 mmol/L/h) often require O2 enrichment.
How does CO2 affect pH in a bioreactor?
CO2 dissolves in media to form carbonic acid, lowering pH through the bicarbonate buffer system. The Henderson-Hasselbalch equation describes this: pH = 6.1 + log([HCO3-] / (0.03 x pCO2)). Adding CO2 to the gas blend lowers pH; stripping CO2 by increasing air flow raises pH. In CHO culture, dissolved CO2 also directly affects cell growth and product quality.
What is vvm and how do I choose the right value?
VVM (vessel volumes per minute) normalizes gas flow to bioreactor volume: vvm = gas flow (L/min) / liquid volume (L). Typical values: 0.01-0.05 vvm for mammalian headspace overlay, 0.5-1.0 vvm for mammalian sparged, 1.0-2.0 vvm for microbial fermentation. Higher vvm increases kLa but also increases foaming, CO2 stripping, and gas costs.
How do I calculate the required O2 enrichment?
First, determine the steady-state requirement: OUR = kLa x (C* - CL). Rearrange to find required C*: C* = OUR/kLa + CL. Since C* is proportional to inlet pO2, the required O2 fraction = C*_required / C*_pure_O2. If this exceeds 20.95% (air), O2 enrichment is needed. Blend pure O2 with air to reach the target composition.
Why use N2 blending for low dissolved oxygen?
For microaerobic or anaerobic fermentations, simply reducing air flow would also reduce mixing and CO2 stripping. Instead, replace air with N2 while maintaining total gas flow. The low pO2 in the blended gas limits oxygen transfer while keeping adequate mixing. This is used for ethanol production, some antibiotic fermentations, and anaerobic cultures.
How do gas costs compare between lab and production scale?
Lab-grade cylinders cost 5-20x more per unit volume than bulk industrial supply. Bulk O2 costs roughly $0.05-0.15/m3 vs $1-3/m3 for lab cylinders. At production scale, on-site N2 generators (PSA) produce N2 for ~$0.02/m3. Gas costs become significant for high-demand processes, especially Pichia fermentation requiring continuous O2 enrichment at high vvm over multi-day runs.