The correct option is A substrates are added to the system all at once and run until the product is harvested
The large scale production of microbial biomass or metabolites is called industrial fermentation.
There are different types of fermentations out of which, batch fermentation is one of them. In this type of fermentation, all the materials necessary for the fermentation like the inoculum (micro-organism) and the substrates are added to the system all at once. All the parameters such as aeration, temperature, pH etc., will be set and the process will be started. Products will be removed only after the process is complete. Neither the substrate will be added nor the product is removed in between till the process is complete. Therefore, this is a closed system.