Characterization and selection of lactic acid bacteria producing β-galactosidase = β-galactosidase 생산 유산균 선별 및 특성 조사

Abstract

This study was carried out to select the lactic acid bacteria producing β-galactosidase (lactase) and investigate the properties of the β-galactosidase. About 100 strains of lactic acid bacteria showing blue colony on the MRS agar medium containing X-gal were isolated from several kinds of Kimchi. Among them, 2 strains were selected as potential β-galactosidase producers. The selected strains, ET-1 and LA-12, were identified as Lactobacillus fermentum and L. acidophilus, respectively by the analysis of 16S rDNA sequences. They showed relatively high β-galactosidase activity and cellular viability. Their β-galactosidase showed the highest activity at 55oC. And the optimum pHs of the enzymes produced by ET-1 and LA-12 were pH 5.5 and pH 7.0, respectively. They were also highly resistant to artificial gastric juice and bile. Two selected strains showed little change of viable cell number for 3 hr incubation in artificial gastric juice, and maintained the viable cell number at 108 CFU/ml for 24 hr in 0.3% oxgall after incubation for 2 hours in artificial gastric juice. Based on these results, ET-1 and LA-12 are expected to be applied in dairy industry.