What type of culture refers to a fixed volume of medium in microbiology?

Batch cultures refer to a fixed volume of medium in microbiology because they involve the growth of microorganisms in a closed system where nutrients are supplied in a single batch and the culture is not replenished during the growth period. In this scenario, the microorganisms consume the nutrients and produce waste products until the resources are depleted or the growth reaches a stationary phase. This closed system is distinct from continuous cultures, where fresh medium is continuously added, and waste products are simultaneously removed, allowing for a steady state of growth.

In the context of batch culture, since the volume of the medium remains constant and is not augmented over time, it allows microbiologists to study the growth and behavior of organisms in a defined environment, making it an essential method in both research and industrial processes such as fermentation.