Which of the following is an advantage of a bioreactor which uses continuous culture system rather than batch culture?

Options

A. It provides required growth conditions like temperature, pH substrate, salts, vitamins and oxygen
B. The transformed recombinant cells are allowed to grow in a large bioreactor till maximum amount of biochemical has been formed.
C. the bioreactor is made empty, cleaned and a fresh medium is added
D. There is a regular drainage of the medium and culture cells from one side and fresh medium from the other side leading to higher yield of desired product

Answer

To determine the advantage of a bioreactor that uses a continuous culture system compared to a batch culture system, we can analyze the options provided:

1. **Option 1**: "It provides required growth conditions like temperature, pH, substrate, salt, vitamins, and oxygen."
- This statement is true for all types of culture systems (batch, fed-batch, and continuous). Therefore, it is not a unique advantage of the continuous culture system.

2. **Option 2**: "The transformed recombinant cells are allowed to grow in a large bioreactor till maximum amount of biochemical has been formed."
- This describes the batch culture system, where cells grow until the nutrients are depleted, and is not an advantage of continuous culture.

3. **Option 3**: "The bioreactor is made empty, clean, and a fresh medium is added."
- This describes a process that is not characteristic of continuous culture. In continuous culture, the system is not emptied; instead, there is a constant flow of fresh medium and removal of waste.

4. **Option 4**: "There is a regular drainage of the medium and culture cells from one side and fresh medium from the other side leading to higher yield of desired product."
- This accurately describes the continuous culture system. In this system, there is a continuous inflow of fresh nutrients and outflow of waste, which maintains optimal growth conditions and leads to higher productivity.

Based on the analysis, the correct answer is **Option 4**: "There is a regular drainage of the medium and culture cells from one side and fresh medium from the other side leading to higher yield of desired product."

### Step-by-Step Solution:
1. **Identify the culture systems**: Understand the differences between batch, fed-batch, and continuous culture systems.
2. **Analyze each option**: Evaluate each provided option to see if it describes a unique advantage of continuous culture.
3. **Eliminate incorrect options**: Discard options that are not specific to continuous culture or describe batch culture characteristics.
4. **Select the correct option**: Choose the option that accurately reflects the advantages of a continuous culture system.