In batch fermentation: A) substrates are added to the system all at once and runs until product is harvested. B) nutrients are continuously fed into the reactor and the product is siphoned off during the run. C) new batches of microorganisms are screened for increase yield. D) small-scale production is used to synthesise product.

Options

A. substrates are added to the system all at once and runs until produce is harvested
B. nutrients are continuously fed into the reactor and the product is siphoned off during the run
C. new batches of microorganisms are screened for increase yield
D. small-scale production is used to synthesise product

Answer

To solve the question regarding batch fermentation, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Fermentation Process**:
- Fermentation is a metabolic process where carbohydrates are converted into alcohols, organic acids, or gases, facilitated by microbial enzymes.

2. **Define Batch Fermentation**:
- In batch fermentation, microorganisms are cultivated in a fixed volume of nutrient medium. This medium contains all necessary nutrients for the microorganisms to grow and produce the desired products.

3. **Process of Substrate Addition**:
- In batch fermentation, substrates (the starting materials) are added to the fermentation system all at once at the beginning of the process.

4. **Consumption of Nutrients**:
- As the microorganisms metabolize the substrates, the concentration of these nutrients decreases while the concentration of the products increases.

5. **Product Accumulation**:
- Unlike continuous fermentation, the products are not siphoned off during the process. Instead, they accumulate in the fermenter until the fermentation process is complete.

6. **Harvesting the Product**:
- Once the fermentation process is finished, the products are harvested from the fermenter.

7. **Identify the Correct Option**:
- Given the explanation, option A states that "substrates are added to the system all at once and runs until product is harvested," which accurately describes batch fermentation.

### Conclusion:
- Therefore, the correct answer to the question is **A) substrates are added to the system all at once and runs until product is harvested.**

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