Harvest Window Predictor

Find the optimal harvest day from VCD, viability, glucose, and lactate trajectories. Integrated rules for CHO mAb, AAV/lentivirus, HEK293, Sf9, and microbial fed-batch.

How to use: pick a process preset (Step 1), paste your daily VCD, viability, glucose and lactate data (Step 2), then tune the trigger thresholds if needed (Step 3). Click Predict harvest day to read the recommended harvest day and window in Step 4. Need to fit μmax from the same data first? Use the Growth Curve Fitter.
1Process preset
Presets set the decision thresholds below. Adjust any threshold to match your process.
2Culture data ?
Tab, comma, or semicolon delimited. First row can be a header (auto-skipped). Leave cells blank (or —) if you don't track a signal.
3Decision rules ?
Viability drop to
Glucose depletion below
Lactate re-accumulation above
IVCD plateau (ΔIVCD < % of peak)
Days after peak VCD
4Harvest-day recommendation
Paste your culture data and click Predict harvest day to see the recommendation.

How the harvest window is calculated

Harvest timing is a multi-signal decision. This tool evaluates up to five independent harvest-trigger rules against your data and returns the earliest day any rule fires — because the first signal to trigger typically defines the quality-limited harvest day.

Rule 1 — Viability floor. Most mAb processes harvest at 70–85% viability. Below the floor, host cell protein and DNA release accelerate; fragmentation and aggregation rise.

Rule 2 — Glucose depletion. Below ~1 g/L, cells enter starvation stress and proteases are released. Either feed or harvest immediately.

Rule 3 — Lactate re-accumulation. After the CHO lactate shift (consumption phase), rising lactate means the culture is losing TCA flux and transitioning to stress. Harvest within 24 h.

Rule 4 — IVCD plateau. Because titer ≈ qP × IVCD, when the daily IVCD increment drops below ~7% of peak daily IVCD, further culture time adds little to final titer but risks quality loss.

Rule 5 — Post-peak VCD. A backup rule: once VCD has fallen for 3 consecutive days after peak, the culture is in death phase regardless of other signals.

Related Tools & Articles

Growth Curve Fitter
Extract μmax, doubling time, lag phase from OD/VCD data
Fed-Batch Calculator
Design exponential feeding profiles and predict biomass
CellTrack
Log timepoints, track VCD, viability, IVCD in real time
Cell Growth Monitoring
Multi-signal biomass tracking in suspension culture
CHO Growth Curve
NI / SI / stationary / death phases and harvest cues
Batch vs Fed-batch vs Perfusion
Process modes and their harvest strategies

Frequently asked questions

When should I harvest a CHO fed-batch bioreactor?
Harvest when viability drops to 70–80%, glucose is depleted below 1 g/L, or the IVCD–titer curve has plateaued for 24–48 h — whichever comes first. The lactate shift (from accumulation to consumption) is a strong positive indicator, but once lactate re-accumulates, harvest within 24 h. Typical CHO mAb fed-batch harvest is day 12–16.
What viability should I harvest at?
Standard mAb processes harvest at 70–85% viability. AAV and lentivirus production often harvest earlier (85–95%) to minimise host cell protein and DNA release. Cell-therapy starting material typically targets ≥ 90%. The threshold trades product titer against product quality.
What is IVCD and how does it relate to harvest timing?
IVCD (integral viable cell density) is the time-integral of VCD, with units of cell-days/mL or cell-hours/mL. Because specific productivity qP is roughly constant over the run, final titer ≈ qP × IVCD. Harvest decisions often target an IVCD setpoint or wait until daily IVCD increment drops below 5–10% of peak.
Why is the lactate shift important for harvest timing?
The lactate shift is when CHO cells switch from producing lactate (glycolysis-dominant) to consuming it (TCA-dominant). It signals the size-increase phase and usually precedes peak titer by 1–3 days. Cultures that re-accumulate lactate after the shift are entering stress — harvest within 24 h is recommended.

Further reading