Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9607679 | Process Biochemistry | 2005 | 4 Pages |
Abstract
The continuous production of extracellular heterologous β-galactosidase by a recombinant flocculating Saccharomyces cerevisiae, expressing the lacA gene (coding for β-galactosidase) of Aspergillus niger was investigated. A continuous operation was run in a 6.5 l airlift bioreactor with a concentric draft tube using lactose as substrate. Data on the operation with semi-synthetic medium with 50 and 100 g/l initial lactose concentrations are presented. The best result for β-galactosidase productivity-6.2Ã105 U/1 h-was obtained for a system operating at 0.24 hâ1 dilution rate and for a lactose concentration in the feed of 50 g/l. This value represents a 11-fold increase in β-galactosidase productivity when compared to batch culture. Together with extracellular β-galactosidase production an ethanol productivity of 9 g/1 h was obtained for the bioreactor fed with 50 g/l initial lactose concentration at 0.45 hâ1 dilution rate. In addition to β-galactosidase and ethanol production, this system allowed for complete lactose metabolism. The feasibility and advantages of using continuous high-cell-density systems operating with flocculent yeast cells for extracellular protein production is clearly shown.
Keywords
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Bioengineering
Authors
LucıÌlia Domingues, Nelson Lima, José A. Teixeira,