A single-use bioreactor is provided. The single-use bioreactor may include a bioprocess container, a shell, at least one agitator, at least one sparger, at least one gas filter inlet port for the sparger(s) and headspace overlay, at least one fill port, at least one harvest port, at least one sample port, and at least one probe. In examples, at least one controller may monitor and control one or more parameters associated with the single-use bioreactor A method to cultivate and propagate mammalian cells is also provided. The method may include cultivating under suitable conditions and in a suitable culture medium in a first single-use bioreactor, transferring the medium containing the cells obtained by propagation from the at least one mammalian cell is into a second single-use bioreactor, transferring the medium containing the cells obtained by propagation from the at least one mammalian cell is into a third single-use bioreactor, and cultivating the cells in the third bioreactor.