Influence of operating conditions and vessel size on oxygen transfer during cellulase production

The production of low-cost cellulase enzyme is a key step in the developmen t of an enzymatic-based process for conversion of lignocellulosic biomass t o ethanol. Although abundant information is available on cellulase producti on, little of this work has examined oxygen transfer. We investigated oxyge n transfer during the growth of Trichoderma reesei, a cellulase-producing m icroorganism, on soluble and insoluble substrates in vessel sizes from 7 to 9000 L. Oxygen uptake rates and volumetric mass transfer coefficients (k(L )a) were determined using mass spectroscopy to measure off gas composition. Experimentally measured k(L)a values were found to compare favorably with a k(L)a correlation available in the literature for a non-Newtonian ferment ation broth during the period of heavy cell growth.