# DBT JRF 2022 — Question 111

Exam: DBT JRF 2022 · Section: B · Topic: Industrial Microbiology › Yeast Fermentation & Cell Reuse · Difficulty: Medium

## Question

Yeast cells obtained from batch fermentation can be reutilized for the production of:

## Options

- **A.** Beer
- **B.** Trypsin
- **C.** Chloramphenicol
- **D.** Acetic acid

## Answer

Option A

## Explanation

Yeast recycling in beer fermentation: In traditional brewing and modern industrial beer production: • After primary fermentation is complete, yeast settles (sedimentation) or can be collected ('cropped'): - Bottom-fermenting (lager) yeast: collects at bottom → 'bottom cropping' - Top-fermenting (ale) yeast: collects at top → 'top cropping' • Collected yeast is washed, stored cold, and used to inoculate subsequent batches. • This 'yeast repitching' can be done multiple times (typically 5–10 generations in commercial brewing; up to 20+ times in traditional breweries). Benefits: • Cost savings (no need to purchase fresh yeast every batch) • Consistency (known, pre-adapted yeast strain) • Faster fermentation start (actively metabolising yeast) Monitoring: Cell viability and vitality are checked (methylene blue staining) before repitching. Answer: Yeast from batch fermentation can be harvested and reused to inoculate subsequent fermentations (yeast repitching).

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