Production of β‐galactosidase from recombinant Saccharomyces cerevisiae grown on lactose

Abstract

Improved productivity and costs reduction in fermentation processes may be attained by using flocculating cell cultures. The production of extracellular heterologous β-galactosidase by recombinant flocculating Saccharomyces cerevisiae cells, expressing the lacA gene (coding for β-galactosidase) of Aspergillus niger under the ADHI promotor and terminator in a bioreactor was studied. The effects of lactose concentration and yeast extract concentration on β-galactosidase production in a semi-synthetic medium were analysed. The extracellular β-galactosidase activity increased linearly with increasing initial lactose concentrations (5-150 g dm −3 ). β-Galactosidase production also increased with increased yeast extract concentration. During the entire fermentation, no accumulation of the hydrolysed sugars, glucose and galactose, was observed. The catabolic repression of the recombinant strain when cultured in a medium containing equal amounts of glucose and galactose was confirmed. In complete anaerobiosis, the fermentation of lactose resulted in a very slow fermentation pattern with lower levels of β-galactosidase activity. The bioreactor operation together with optimisation of culture conditions (lactose and yeast extract concentration) led to a 21-fold increase in the extracellular β-galactosidase activity produced when compared with preliminary Erlenmeyer fermentations.

Isolation and Production of Novel β-galactosidase from a Newly Isolated, Moderate Thermophile, Bacillus sp. Strain B1.1

“…Our results agreed with those observed for Streptococcus thermophilus and Kluyveromyces lactis by Rao and Dutta [16] and Barreto et al [5], respectively, who demonstrated that peptone can be a good nitrogen source which that a maximum synthesis of β-galactosidase. On the other hand, these results were different from the report of Domingues et al [17] and Hsu et al [9], which indicated that the highest activity of this enzyme was obtained by Aspergillus niger and Bifidobacterium longum CCRC 15708, respectively, when using yeast extract. A further increase in β-galactosidase activity was observed with an increase in the peptone concentration in the medium, and a maximum activity was obtained in the presence of 20 g L -1 peptone.…”

Recombinant microbial systems for improved β-galactosidase production and biotechnological applications

“…Thus, this recombinant system allows for the bioremediation of cheese whey and β-galactosidase production simultaneously. Using optimized operation and culture conditions a 21-fold increase in β-galactosidase production was attained in a 10-L bioreactor, comparing with the previous fermentations conducted in Erlenmeyer flasks (Domingues et al, 2004; Table 1). The percentage of β-galactosidase secreting cells at the end of fermentations was greater than 70%.…”

“…Therefore, optimization of the large-scale production of A. niger recombinant β-galactosidase was conducted with this recombinant yeast strain. The production of recombinant β-galactosidase in a 2-L bioreactor with controlled agitation, aeration, pH and temperature was carried out varying the lactose and yeast extract concentrations in semi-synthetic medium (SSlactose) (Domingues et al, 2002;Domingues et al, 2004). The recombinant β-galactosidase activity increased linearly with increasing lactose concentrations (between 0.5 and 15% (w/v)), as well as with increasing yeast extract concentrations (between 0.2 and 1.5% (w/v)).…”

Metabolic engineering ofSaccharomyces cerevisiaefor lactose/whey fermentation

“…79 To improve the genetic stability of the strains the lacA gene expression cassette was targeted to the δ-sequences in the genome. 80 Even though our main goal was to produce heterologously A. niger β-galactosidase, we have observed that these strains produced ethanol from lactose/whey with close to theoretical yields in batch 78 and in high-cell-density continuous fermentations 81 with complete lactose utilisation ( Table 2).…”