Stirred-tank bioreactors have been designed for
Availability of oxygen throughout the process
Addition of preservatives to the product
Purification of the product
Ensuring anaerobic conditions in the culture vessel
Stirred-tank bioreactors use an air compressor. The compressor generates air pressure to force the air through the filter, holes and into the liquid and thereby ensuring the continuous supply of oxygen throughout the process.
Hence, the correct answer is 'Availability of oxygen throughout the process'