Q.29 In an exponentially growing batch culture of
Saccharomyces cerevisiae, the cell density is
20 g l−1 (DCW), the specific growth rate (μ) is
0.4 h−1 and substrate uptake rate (v) is
16 g l−1 h−1. The cell yield coefficient
Yx/s will be
Calculation of Cell Yield Coefficient (Yx/s) in an Exponentially Growing Yeast Culture
In microbial biotechnology and bioprocess engineering, the
cell yield coefficient (Yx/s) is an important parameter that relates
biomass formation to substrate consumption. This type of numerical problem is
frequently asked in competitive exams such as GATE, CSIR-NET,
and ICAR.
Given Data
- Organism: Saccharomyces cerevisiae
- Cell density (X): 20 g L-1 (DCW)
- Specific growth rate (μ): 0.4 h-1
- Substrate uptake rate (ν): 16 g L-1 h-1
Formula Used
The cell yield coefficient is defined as:
Yx/s = (Rate of biomass formation) / (Rate of substrate consumption)
Mathematically:
Yx/s = (μ × X) / ν
Step-by-Step Calculation
Step 1: Biomass formation rate
μ × X = 0.4 × 20 = 8 g L-1 h-1
Step 2: Cell yield coefficient
Yx/s = 8 / 16 = 0.50
Correct Answer
Option (D): 0.50
Key Concept Summary
- Yx/s measures substrate-to-biomass conversion efficiency
- Depends on μ (specific growth rate), X (biomass concentration), and ν (substrate uptake rate)
- Widely used in fermentation kinetics and bioprocess design
Conclusion
The cell yield coefficient (Yx/s) for the exponentially growing batch culture
of Saccharomyces cerevisiae is 0.50. Therefore,
Option (D) is the correct answer.
