Screening of -Galactosidase-producing Lactic Acid Bacteria and Analysis of the Enzymatic Synthesis of Galactooligosaccharides by GC-MS
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Abstract:
Lactic acid bacteria (LAB) strains producing ?-galactosidases with high transgalactosylation activity were screened from 148 LAB strains found in 13 kinds of traditional Chinese fermented foods. The strain 70810 produced ?-galactosidases with the highest transgalactosylation activity and was isolated using a 5-bromo-4-chloro-3-indolyl β-D-galactopyranoside (X-Gal) plate for the primary screening, thin layer chromatography (TLC) for the secondary screening, and gas chromatography (GC) for quantitation. Lactose was used as a single substrate, the synthesis of galactooligosaccharides (GOS) was catalyzed by ?-galactosidases with high transgalactosylation activity, and gas chromatography-mass spectrometry (GC-MS) was used to identify each component. The results showed that the ?-galactosidases produced by strain 70810 had the highest transgalactosylation activity, and the yield of GOS was 39.23 % (m/m). This LAB strain was identified as Lactobacillus plantarum (HQ259238). Among the GOS products derived from enzymatic synthesis, there were nine disaccharides and three trisaccharides and the main structures contained ?-1,6 and ?-1,3 glycosidic bonds. Because strain 70810 was isolated from Chinese Paocai, it is safe. The resulting ?-galactosidases have the highest transgalactosylation activity and can be directly used without separation and purification. Therefore, this strain has potential applications in food and dairy industries.
