Difference Between Batch and Continuous Culture

The main difference between batch and continuous culture is that batch culture is a closed system that carries out fermentation with a fixed amount of nutrients whereas continuous culture is an open system, which continuously carries out fermentation. Furthermore, nutrients become a limiting factor after a certain point in a batch culture while nutrients are continuously supplied to the continuous culture, maintaining the optimum conditions for the fermentation. 

Batch and continuous culture are two types of industrial fermentation used for the production of microbial biomass or metabolites. 

Key Areas Covered 

1. What is a Batch Culture
     – Definition, Facts, Importance
2. What is a Continuous Culture
     – Definition, Facts, Importance
3. What are the Similarities Between Batch and Continuous Culture
     – Outline of Common Features
4. What is the Difference Between Batch and Continuous Culture
     – Comparison of Key Differences

Key Terms

Advantages, Batch Culture, Continuous Culture, Disadvantages, Process 

What is a Batch Culture 

A batch culture is a closed culture where microorganisms ferment a given amount of nutrients within a defined time period. The optimal pH and the aeration are provided for these microorganisms. The fermentation takes place in batches. That means the products are removed at the end of one fermenting session and the fermenter is filled with the nutrients for the second fermenting session.

Figure 1: Batch Culture

The advantages of batch culture are the easy setup and control of the cultures and the ability to carry out different cultures at different times.  

What is a Continuous Culture 

A continuous culture is an open culture in which the supply of nutrients, as well as the removal of the products, is continuous. Here, the microorganisms maintain an exponential growth since fresh media is added continuously. Hence, most of the bacteria are in their log phase.

Figure 2: Continuous Culture  

The advantages of continuous culture are continuous fermentation and high productivity. But, different cultures cannot be fermented in the same fermenter. Also, continuous cultures are more prone to be contaminated. 

Similarities Between Batch and Continuous Culture 

• Batch and continuous culture are two types of industrial cultures used for the production of microbial biomass or metabolites. 
• Both are involved in the large-scale production.  
• The conditions inside the culture are controlled as required. 
• The structure of both cultures is similar. 

Difference Between Batch and Continuous Culture 

Definition 

Batch culture refers to a technique used to grow microorganisms in a limited supply of nutrients, which declines when these are used up, or some other factor becomes limiting while continuous culture refers to a technique used for the production of microbes or microbial products in which nutrients are continuously supplied to the fermenter.

Open/Closed System 

Batch culture is a closed system while continuous culture is an open system.

Internal Environment 

The internal environment of batch culture is changed with the progression of the fermentation process while the environment of the continuous culture is not changed during the fermentation process.  

Nutrients 

Nutrients are added at the beginning of the process in batch culture while nutrients are continuously added to the continuous culture throughout the process. Nutrients become a limiting factor at some point in a batch culture while nutrients are not a limiting factor in a continuous culture. This is a key difference between batch and continuous culture.

Phases 

Lag, log, and stationary phases occur in a batch culture while lag and log phases are maintained in a continuous culture. 

Continuity 

The whole process is stopped when the products are formed in a batch culture while the process continues and the products are continuously removed from the fermenter in a continuous culture. 

Yield 

The yield of the batch culture is low while the yield of the continuous culture is significantly high.  

Turnover Rate 

Turnover rate is low in batch cultures while the turnover rate is high in continuous cultures. 

Suitable for 

Batch culture is suitable for the production of secondary metabolites such as antibiotics while continuous culture is suitable for the production of primary metabolites such as organic acids and amino acids. 

Labor Demand 

Labor demand is less in a batch culture while labor demand is more in continuous culture. 

Chance of Contamination 

The chance of contamination is less in a batch culture while the chance of contamination is high in batch culture.  

Fermenter Size 

Large fermenters are used for batch cultures while small fermenters are used for the continuous cultures. 

Conclusion 

Batch culture operates within a certain period of time and products are removed at the end of the process. But, continuous culture operates continuously as fresh media are added to the fermenter. So, nutrients are not a limiting factor in a continuous culture. However, nutrients become a limiting factor at a certain period of time in a batch culture. 

Reference:

1. Karki, Gaurab. “Cultivation Technique of Bacteria: Batch, Fed-Batch and Continuous Culture Technique.” ONLINE BIOLOGY NOTES, 20 Dec. 2017, Available Here  

Image Courtesy:

1. “Auxostat schematic” By GYassineMrabetTalk✉ – Own work (CC BY-SA 3.0) via Commons Wikimedia   
2. “Chemostat shematic” By GYassineMrabetTalk✉ – Own work based on Chemostatdiagram.png (Rintze Zelle) (Public Domain) via Commons Wikimedia