Expression of the β-(1,3-1,4)-glucanase gene in Streptococcus salivarius subsp thermophilus

The purpose of this study was the transformation and expression of the beta-(1,3-1,4)-glucanase (lichenase) gene in Streptococcus salivarius subsp. thermophilus to create a recombinant probiotic for poultry and improve the thermostability of the lichenase enzyme. The recombinant plasmid TL1R containing the beta-(1,3-1,4)-glucanase gene was introduced into S. salivarius subsp. thermophilus by electrotransformation. The expressing of the beta-(1,3-1,4)-glucanase gene in S. salivarius subsp. thermophilus was confirmed on lichenan plate, SDS-PAGE, and zymogram analysis. The beta-(1,3-1,4)-glucanase enzyme expressed by S. salivarius subsp. thermophilus cells seemed to increase its capacity for thermoresistance and so it maintained its activity at 70 degrees C for 15 min. In contrast, the enzyme produced by Lactococcus lactis and Escherichia coli cells easily ceased activity when exposed to the same temperature. The enzyme expressed by all the recombinant bacteria resisted denaturation and somehow remained soluble after heat treatment from 37 to 100 degrees C for 15 min.