Effect of aeration and agitation on growth rate of Thermus thermophilus in batch mode

Abstract

The growth kinetics of Thermus thermophilus HB27 was investigated in rich medium ( Thermus medium) under batch cultivation at 65°C in 3- l fermentors. The growth and oxygen consumption rates were highly dependent on the aeration and agitation rates. Volumetric mass transfer coefficient ( K L a, h −1) and hence oxygen transfer rate (OTR, mol m −3 h −1) into the fermentation broth increased with increased aeration and/or agitation rates. A K L a and OTR of 175.4 h −1 and 31.7 mol m −3h −1 respectively, corresponding to 500 rpm agitation and2 vvm aeration with a mixture of air and oxygen, were required to avoid oxygen limitation. The maximum growth rate ( μ max, h −1), doubling time ( t D, h), and dry cell weight determined for T. thermophilus HB27 growing under these conditions were 0.27 h −1, 2.67 h, and 3 g/l respectively. This cell yield is higher than any previously published reports for growth of Thermus cultures, including studies that employed pressurized bioreactors.