[Construction and property study of recombinant Lactococcus lactis with non-fusion expressing of beta-galactosidase].

OBJECTIVE

To construct recombinant Lactococcus lactis strains exhibiting high beta-galactosidase activity in non-fusion way, and study their enzyme activities and enzyme secretion rates.

METHODS

The recombinant plasmids pMG36e-lacZ 1.1480 and pMG36e-lacZ wch9901 which could express beta-galactosidase from Lactobacillus delbrueckii subsp. bulgaricus in non-fusion way in Escherichia coli were obtained and transformed into Lactococcus lactis subsp. lactis MG1363. The beta-galactosidase activity of resulting recombinant L. lactis in different incubation periods and lactose concentrations, and their enzyme secretion rates in different culture conditions were examined.

RESULTS

Recombinant L. lactis carrying pMG36e-lacZ wch9901 (MG1363/pMG36e-lacZ wch9901) exhibited the highest beta-galactosidase activity. Its enzyme activity was (16.95 +/- 0.09) U/mg pro, which was 2.75 folds of that of the native counterpart; recombinant L. lactis reached its enzyme producing peak after grown for 24 h; decreased enzyme activity of recombinant L. lactis were observed when incubated in medium containing lactose; the beta-galactosidase expressed by recombinant strains could be secreted into the culture medium, and the highest secretion rate (27.09 +/- 0.05)% was observed when the culture medium contained 20 g/L of lactose and without erythromycin.

CONCLUSION

High level expression of non-fusion beta-galactosidase with secretion in recombinant L. lactis strains was obtained. This will be very helpful for the further developing of live delivery bacteria of beta-galactosidase.