초록
Oxygenation is an important parameter involved in the design and operation of mixing-sparging bioreactors and it can be analyzed by means of the oxygen mass transfer coefficient (k<SUB>L</SUB>a). In this study, batch fermentations in stirred tank bioreactor (STB) and airlift bioreactor (ALB) were operated under a range of k<SUB>L</SUB>a values, in attempts to optimize and compare the activities of extracellular xylanase and β-xylosidase synthesized by the fungus Aspergillus niger van Tieghem, using corncob as inducer source. The higher xylanase levels were observed on STB (9000Ul<SUP>-1</SUP>; k<SUB>L</SUB>a=30h<SUP>-1</SUP>), while the β-xylosidase production was similar in both bioreactors. However, when the enzymatic activity was compared for the same k<SUB>L</SUB>a value (12h<SUP>-1</SUP>) in STB and ALB, the xylanase and β-xylosidase productions were higher in ALB (7000Ul<SUP>-1</SUP> xylanase; 2100Ul<SUP>-1</SUP> β-xylosidase) than STB (4500Ul<SUP>-1</SUP> xylanase; 1800Ul<SUP>-1</SUP> β-xylosidase).