• Microbiology and Biotechnology Letters
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• v.37 no.4
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• pp.389-398
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• 2009

Development of expression vectors is important for the basic and applied researches on kimchi LAB (lactic acid bacteria). An expression vector, pSJE6c was constructed by inserting P6C promoter sequence from Lactococcus lactis into pSJE, a shuttle vector for E. coli and Leuconostoc species. To test the efficiency of pSJE6c, aga ($\alpha$-galactosidase) and lacZ ($\beta$-galactosidase) genes were expressed in Lactobacillus brevis 2.14. Compared to the pSJE, expression levels of both genes were increased, indicating P6C promoter was better than indigenous promoters. Enzyme activities of L. brevis cells harboring pSJE6caga (pSJE6c with aga) or pSJE6Z (pSJE6c with lacZ) were 1.5-2 fold higher than those with pSJEaga (pSJE with aga) or pSJEZ (pSJE with lacZ). More RNA transcripts were detected in cells harboring pSJE6c based recombinant plasmid. The results indicated that heterologous gene expressions in kimchi LAB could be improved significantly by use of efficient expression vectors.

• Food Science and Biotechnology
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• v.17 no.5
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• pp.1115-1118
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• 2008

${\alpha}$-Galactosidase gene (aga) from Leuconostoc mesenteroides SY1 was expressed in a heterologous host, Lactobacillus brevis 2.14 using an Escherichia coli-Leuconostoc shuttle vector, pSJE. pSJEaga (pSJE carrying aga) was introduced into Lactobacillus brevis 2.14 by electroporation and transformation efficiency was $1.1{\times}10^3$ per ${\mu}g$ DNA. L. brevis transformants (TFs) showed higher ${\alpha}$-galactosidase (${\alpha}$-Gal) activities than cells containing pSJE. Transcription levels of aga in L. brevis 2.14 grown on different carbon sources (1%, w/v) were examined by slot blot analysis. Aga transcript levels and ${\alpha}$-Gal activities were higher in cells grown on melibiose, raffinose, and galactose than cells on glucose, sucrose, and fructose. Western blot result showed that L. brevis 2.14 harboring pSJEaga produced much more ${\alpha}$-Gal when grown on melibiose than on glucose.

• Preventive Nutrition and Food Science
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• v.13 no.3
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• pp.190-195
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• 2008

The $\alpha$-amylase gene, amyL, from Bacillus licheniformis was expressed in Lactobacillus brevis 2.14 and Escherichia coli $DH5{\alpha}$ using two different shuttle vectors, pCW4 and pSJE. E. coli transformants (TFs) harboring either $pCW4T{\alpha}$ or $pSJET{\alpha}$ produced active $\alpha$-amylase but L. brevis TFs did not, as determined by enzyme assays and zymography. But amyL transcripts were synthesized in L. brevis TFs. In terms of plasmid stability, pSJE, a theta-type replicon, was more stable than pCW4, an RCR (rolling circle replication) plasmid, in L. brevis without antibiotic selection.

• Journal of Microbiology and Biotechnology
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• v.17 no.12
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• pp.2081-2084
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• 2007

A 2.5 kb aga gene encoding ${\alpha}$-galactosidase (${\alpha}$-Gal) from Leuconostoc mesenteroides SY1 was cloned into pSJE, an E. coli-Leuconostoc shuttle vector. The recombinant plasmid, pSJEaga, was introduced into Leuconostoc citreum KCTC3526 (ATCC49370) by electroporation. Transcription level of aga was the highest in cells grown on raffinose (1%, w/v) followed by cells grown on galactose, melibiose, fructose, glucose, and sucrose. Western blot using antibodies against ${\alpha}$-Gal showed similar results to slot-blot results and enzyme activity measurements. All the results indicated that the aga was successfully expressed in L. citreum and its transcription was under the carbon catabolite repression (CCR).