# DBT JRF 2020 — Question 119

Exam: DBT JRF 2020 · Section: B · Topic: Bioprocess Engineering · Difficulty: Medium

## Question

In large scale fermentation processes, corn steep liquor is mainly used as a

## Options

- **A.** carbon source
- **B.** nitrogen source
- **C.** carbon and vitamin source
- **D.** vitamin and micronutrient source

## Answer

Option B

## Explanation

Corn steep liquor (CSL) is a byproduct of corn wet milling (steeping corn kernels in warm water + $\text{SO}_2$ for 24–48 h). CSL is rich in: proteins and amino acids (~45% of dry weight) — PRIMARY USE: nitrogen source in fermentation media; vitamins (especially thiamine/B1); minerals (K, Mg, Ca, Zn, Fe); lactic acid (from Lactobacillus contamination during steeping). CSL is used as a cheap, complex nitrogen and growth factor source for producing: Penicillin (Fleming/Coghill’s WWII production); lysine; glutamate; riboflavin; many industrial enzymes. CSL replaced cottonseed flour and soybean meal as the preferred nitrogen source. It is NOT primarily used as a carbon or vitamin source — dextrose (corn starch hydrolysate) provides carbon.

Source: https://mypyqbuddy.com/questions/in-large-scale-fermentation-processes-corn-steep-liquor-6a05a8a02adafec47029328f