This book compares tow perfusion based bioprocesses for their ability to use lower temperature and pH- values to improve volumetric productivity after an initial growth phase under standard conditions. For that CHO cells cultivated on microcarriers with a fluidised bed reactor were compared against CHO cells suspended in a continuously stirred tank reactor with an ultrasonic cell retention device. Cell culture conditions were changed to a temperature of 33 degrees Celsius and a pH-value of 6.9 in the later cultivation phase. This led to reduced media consumption and increased volumetric productivity.