• Journal of Microbiology and Biotechnology
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• v.9 no.4
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• pp.393-397
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• 1999

The gene (galE) encoding UDP-galactose-4-epimerase, operative in the galactose metabolic pathway, was cloned together with the $\beta$-galactosidase gene (lacZ) from Lactococcus lactis ssp. lactis ATCC7962 (L. lactis 7962). galE was found to have a length of 981 bps and encoded a protein with a molecular mass of 36,209 Da. The deduced amino acid sequence showed a homology with GalE proteins from several other microorganisms. A Northern analysis demonstrated that galE was constitutively expressed by its own promoter. When galactose or lactose was added into medium, the galE transcription was induced by several upstream promoters. The structure of the gal/lac operon of L. lactis 7962 was partially characterized and the gene order around galE was galT-lacA-lacZ-galE-orfX.

• Journal of Microbiology and Biotechnology
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• v.1 no.1
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• pp.12-16
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• 1991

Previously RP1::Tn951 which is a derivative of RP1 containing the lactose transposon Tn951 was introduced into Z. mobilis strain ZM6l00, and RP1::Tn951 was integrated into its genome to yield ZM6306. The galactose operon was incorporated into ZM6306 to yield ZM6307 for more efficient utilization of lactose. Batch culture study has been carried out on Z. mobilis strains, ZM6306 ($lac^+$ ) and ZM6307 ($lac^+$ , $gal^+$ ), which can convert lactose directly to ethanol. Using a medium containing 80 gㆍ$1^{-1}$ glucose and 40 gㆍ$1^{-1}$ lactose, it was found that ZM6306 and ZM6307 produced maximum ethanol concentration of 40 gㆍ$1^{-1}$ and 42 gㆍ$1^{-1}$, respectively, whereas parent strain ZM6 produced 37 gㆍ$1^{-1}$.

• Journal of Microbiology and Biotechnology
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• v.10 no.6
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• pp.840-843
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• 2000

The structure of gal/lac operon of Lactococcus lactis ssp. lactis ATCC7962 was partially characterized and the gene (galM) encoding galactose mutarotase was cloned together with the order; galA-galM-galK-galT. The galM was found to be 1,027 bp in length and encoded the protein of 37,609 Da calculated molecular mass. The deduced amino acid sequence showed a homology with GalM proteins from several other microorganisms. Thus, the galM gene was expressed in Escherichia coli and the product was identified as a 38 kDa protein which corresponded to the size estimated from DNA sequence. mutarotase activity of the IPTG inducedrecombinant was 2.7 times increased against that of the host strain.

• Journal of Microbiology
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• v.40 no.2
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• pp.156-160
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• 2002

The whole gal/lae operon genes of Lactococcus lactis ssp. lactis 7962 were reported as follows: galA-galM-galK-galT-lacA -lacZ-galE. The galK gene encoding a galactokinase involved in one of the Leloir pathways for galactose metabolism was found to be 1,197 bp in length and encodes a protein of 43,822 Da calculated molecular mass. The deduced amino acid sequence showed over 50% homology with GaIK proteins from several other lactic acid bacteria. The galK gene was expressed in E. coli and the product was identified as a 43 kDa protein which corresponds to the estimated size from the DNA sequence. The galactokinase activity of recombinant 5. coli was about 8 times greater against that of the host strain and more than 3 times higher than the induced L. lactis 7962.

• Microbiology and Biotechnology Letters
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• v.48 no.3
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• pp.287-295
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• 2020

Lactobacillus zymae GU240 was previously isolated from Kimchi, a Korean fermented vegetable, as a strong GABA producer. The strain showed β-galactosidase (β-Gal) activity on MRS agar plates with X-gal. When growth and β-Gal activities of GU240 were measured using MRS (glucose, 2%, w/v) and MRSL (lactose, 2%, w/v) broths, cells were found to grow slowly in MRSL, and the β-Gal activity (36 units at 4 h) was lower than that of cells grown in MRS (94 units at 16 h). The highest OD₆₀₀ value of the culture in MRS was 1.6 at 24 h at 37℃, whereas that of the culture in MRSL was 0.6 at 16 h. β-Gal activity of the culture in MRS reached the maximum (95.6 u/ml) at 16 h, decreased thereafter, and was not detected at 48 h. β-Gal activity for culture in MRSL reached its highest (36 u/ml) at 4 h and decreased gradually, but some activity (11.05 u/ml) still remained at 72 h. The structural gene encoding β-Gal in L. zymae GU240 was cloned as a 3.1 kb fragment, and DNA sequencing confirmed the presence of complete lacLM genes. lacLM genes from L. zymae GU240 showed 98-99% homologies in nucleotide sequences with other lacLM genes from L. brevis. Reverse transcription (RT)-PCR confirmed the operon structure of lacLM. The results indicated that L. zymae GU240 might be in the process of losing the ability to grow rapidly on lactose-containing medium, such as milk, due to adaptations to plant environments, including kimchi.

• Journal of Microbiology and Biotechnology
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• v.12 no.1
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• pp.157-161
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• 2002

A lactic acid bacteria with ${\beta}$-gal activity was isolated from Kimchi, a traditional fermented vegetable food in Korea. The isolate was identified as a Lactococcus lactis strain and named L. lactis A2. The gene encoding ${\beta}$-gal of L. lactis A2 was cloned as a 5.8 kb PstI fragment. DNA sequencing identified the complete lacA (galactoside acetyltransferase)-lacZ (${\beta}$-galactosidase) genes together with the 3' part of upstream galT (galactose-1-phosphate uridyltransferase), and the 5'region of downstream galE (UDP-galactose-4-epimerase) genes. L. lactis A2 had the same gal/lac operon structure as in L. lactis subsp. lactis 7962. Other genes of the Leloir pathway are most likely to be located in the 5'upstream of the 5.8 kb fragment on the A2 chromosome. Sequences downstream of galE were different from those of L. lactis subsp. lactis 7962.