Characterization of lactose utilization and β-galactosidase in Lactobacillus brevis KB290, the hetero-fermentative lactic acid bacterium

Hiroyuki Honda, Nobuhiro Yajima, Tadao Saito

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Unlike dairy lactic acid bacteria, Lactobacillus brevis cannot ferment milk. We characterized the lactose utilization by L. brevis KB290. In a carbohydrate fermentation assay using API 50 CHL, we showed during 7 days L. brevis did not ferment lactose. L. brevis grew to the stationary phase in 2 weeks in MRS broth containing lactose as the carbon source. L. brevis slowly consumed the lactose in the medium. L. brevis hydrolyzed lactose and a lactose analog, o-nitrophenyl-β-D-galactopyranoside (ONPGal). This β-galactosidase activity for ONPGal was not repressed by glucose, galactose, fructose, xylose, or maltose showing the microorganism may not have carbon catabolite repression. We purified the L. brevis β-galactosidase using ammonium sulfate precipitation and several chromatographies. The enzyme's molecular weight is estimated at 72 and 37 kDa using SDS-PAGE analysis. The N-terminal amino acid sequence of the larger protein was 90 % similar to the sequence of the putative β-galactosidase (YP-796339) and the smaller protein was identical to the sequence of the putative β-galactosidase (YP-796338) in L. brevis ATCC367. This suggests the enzyme is a heterodimeric β-galactosidase. The specific activity of the purified enzyme for lactose is 55 U/mg. We speculate inhibition of lactose transport delays the lactose utilization in L. brevis KB290.

Original languageEnglish
Pages (from-to)679-685
Number of pages7
JournalCurrent Microbiology
Volume65
Issue number6
DOIs
Publication statusPublished - 2012 Dec

ASJC Scopus subject areas

  • Microbiology
  • Applied Microbiology and Biotechnology

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