The effects of oxygen transfer on serine alkaline protease (SAP) production by Bacillus licheniformis on a defined
medium with Cc 5 9.0 kg m23 citric acid as sole carbon source were investigated in 3.5 dm3 batch bioreactor
systems. The concentrations of the product (SAP) and by-products, i.e., neutral protease, amylase, amino acids,
and organic acids were determined in addition to SAP activities. At Qo/V 5 1 vvm air flow rate, the effect of
agitation rate on DO concentration, pH, product, and by-product concentrations and SAP activity were
investigated at N 5 150, 500, and 750 min21
transfer (HOT) conditions. LOT conditions favor biomass concentration; however, substrate consumption was
highest at HOT conditions. MOT was optimum for maximum SAP activity which was 441 U cm23 at t 5 37 h.
The total amino acid concentration was maximum in LOT and minimum in MOT conditions; lysine had the
highest concentration under all oxygen transfer conditions. Among organic acids, acetic acid had the highest
concentration and its concentration increased with oxygen transfer rate. The oxygen transfer coefficient increases
with the agitation rate and the oxygen consumption rate increased almost linearly with the biomass
concentration. © 1998 Elsevier Science Inc.
; these are named as low-(LOT), medium-(MOT), and high oxygen