A flocculent Saccharomyces cerevisiae strain
secreting Aspergillus niger β-galactosidase activity was
constructed by transforming S. cerevisiae NCYC869-A3
strain with plasmid pVK1.1 harboring the A. niger β-galactosidase
gene, lacA, under the control of the ADH1
promoter and terminator. Compared to other recombinant
S. cerevisiae strains, this recombinant yeast has higher
levels of extracellular β-galactosidase activity. In shakeflask
cultures, the β-galactosidase activity detected in the
supernatant was 20 times higher than that obtained with
previously constructed strains (Domingues et al. 2000a).
In bioreactor culture, with cheese-whey permeate as substrate,
a yield of 878.0 nkat/gsubstrate was obtained. The
recombinant strain is an attractive alternative to other
fungal β-galactosidase production systems as the enzyme
is produced in a rather pure form. Moreover, the use of
flocculating yeast cells allows for enzyme production
with high productivity in continuous fermentation systems
with facilitated downstream processing.Instituto de Biotecnologia e Química Fina (IBQF).Fundação para a Ciência e a Tecnologia (FCT) – PRAXIS XXI/BD/11306/97
