Q.60 At the end of a batch culture, glucose solution is added at a flow rate of 200 ml/h. If the
culture volume after 2 h of glucose addition is 1000 ml, the initial culture volume (in ml)
is _________
Calculate Initial Culture Volume in Fed-Batch Process
Glucose addition at 200 ml/h for 2 hours increases the batch culture volume to 1000 ml, making this a classic fed-batch transition problem. The initial volume is 600 ml, determined by subtracting the added feed volume.
Key Concept
In batch culture, the initial volume V₀ remains constant until feed starts. Here, glucose solution flows at a constant rate F = 200 ml/h without outflow, so after time t = 2 h, final volume V_f = V₀ + F × t.
Substituting values: 1000 = V₀ + 200 × 2, so V₀ = 1000 – 400 = 600 ml
Step-by-Step Solution
The process converts batch to fed-batch by continuous nutrient addition.
- Feed volume added: 200 ml/h × 2 h = 400 ml
- Initial volume: 1000 – 400 = 600 ml
- This assumes no evaporation or sampling dilution, standard for such exam problems.
Common Mistakes Explained
Students often confuse this with chemostat (continuous) culture or dilution factors.
Why Fed-Batch Matters
Fed-batch extends batch culture by controlled feeding to avoid substrate inhibition, common in microbial or CHO cell processes for higher yields. Glucose spikes can cause overflow metabolism, so timed addition maintains growth.
