Comparisons between cellulase production by Aspergillus fumigatus in agitated vessels and in an air‐lift fermentor

Abstract

Aspergillus fumigatus was cultured in disc-turbine-agitated vessels and in an air-lift fermentor. In the agitated vessels the yield of cellulase was reduced when the agitation rate was increased, although extracellular protein levels rose. The enzyme complex itself was shown to be exceptionally stable under conditions similar to those in the agitated vessels, so probably shear damage to the mycelium had occurred, liberating intracellular contents. These appeared to contain an inhibitor that could be removed by fabricated inorganic protein absorbents, such as kieselguhr and alumina. However, the inhibitor was not likely to be protease, since only relatively low levels could be detected and its identity has not been established. The use of an air-lift fermentor avoided the shear effects due to use of the disc turbine agitator in the conventional fermentors, and yields of enzyme were then found to increase by about 20%, maximum yields being obtained at maximum K(L)a values.

Lignocellulose biotechnology: issues of bioconversion and enzyme production

“…To date, the production of cellulase and other lignocellulosic enzymes have been widely studied in submerged culture processes in the laboratory, ranging from shake flask to 15 000-l fermentations (Haltrich et al, 1996;Kim et al, 1997;Xia and Len, 1999). A stirred-tank reactor, widely used for the production of cellulose and other lignocellulosic enzymes, is known to have shear problems which rupture mycelial cells and may deactivate the enzymes (Wase et al, 1985). Alternative bioreactors such as the air-lift or bubble-column, which have a lower shear stress, seem to produce better results.…”

Bioreactors: Airlift Reactors

“…The reason for the more successful growth reported in ALRs (5)(6)(7)(8)(9)(10)(11)(12)(13)(14) appears to lie in the difference in the fluid dynamics of ALRs and STRs. In conventional STRs, the energy required for the movement of the fluids is introduced focally at a single point in the reactor, via a stirrer.…”

Production of Value-Added Products from Meat Processing Cellulosic Waste

“…Common types of aerobic reactors that have been studied for the production of cellulase are the stirred-tank, stirred-tank with microbubble, air-lift, and bubble column reactors (Wase et al, 1985;Kim et al, 1997;Weber and Agblevor, 2005). Stirred-tank reactors have been shown to cause shear problems, rupturing mycelial cells and deactivating cellulase enzymes (Wase et al, 1985).…”

“…Stirred-tank reactors have been shown to cause shear problems, rupturing mycelial cells and deactivating cellulase enzymes (Wase et al, 1985). Kim et al (1997) compared different types of reactors for the production of cellulase using ground rice straw as a substrate.…”