A 250 ml (0.25 L) batch of curd is prepared using a starter culture containing Lactobacillus delbrueckii subsp. bulgaricus. The culture ferments lactose at a rate of 0.015 g per litre per hour. If the fermentation lasts 5 hours, how much lactose is converted to lactic acid in grams?
Answer
0.01875 g
The correct answer is 0.01875 g — Multiply by fermentation time (5 h) to obtain total conversion: 0.00375 × 5 = 0.01875 g.
Step-by-step solution
- Rate of lactose conversion is given per litre per hour: 0.015 g/(L·h).
- Convert batch volume to litres: 250 ml = 0.25 L.
- Multiply rate by volume to get g/h: 0.015 × 0.25 = 0.00375 g/h.
- Multiply by fermentation time (5 h) to obtain total conversion: 0.00375 × 5 = 0.01875 g.
Common mistake: Forgetting to include the fermentation time or mixing up units of volume
Concept tested: Rate calculation in microbial fermentation
Published · How this solution was prepared and checked
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