Formation of galactooligosaccharides by ${\beta}-galactosidase$ from Streptococcus thermophilus 510

Streptococcus thermophilus 510의 ${\beta}-galactosidase$에 의한 galactooligosaccharides의 생성에 관한 연구

The formation of galactooligosaccharides by transgalactosidation reactions during hydrolysis of lactose by the ${\beta}-galactosidase$ from Streptococcus thermophilus 510 was investigated. Three oligosaccharides were detected during hydrolysis. It was found that the optimum conditions for the production of oligosaccharides was 40% lactose treated with ${\beta}-galactosidase(50\;ONPG\;units/ml)$ at $37^{\circ}C$ for 4 hours. The oligosaccharides formed accounted for 30% of the total sugars when the lactose had been 94% hydrolysed. 69% of the oligosaccharides were identified as $6-o-{\beta}-D-galactopyranosyl-D-glucose(allolactose)$ and 23% as $6-o-{\beta}-D-galactopyranosyl-D-galactose(isogalactobiose)$. The separation of galactooligosaccharides by the use of Bio-Gel P-2 gel permeation chromatography was also studied.

Streptococcus thermophilus 510의 ${\beta}-galactosidase$는 유당을 가수분해 하는 동시에 galactose전이반응을 일으켜 세 종류의 galactooligosaccharides를 형성 하였다. Oligosaccharide의 최대 생성 조건은 40% 유당 용액에 효소 50 ONPG units/ml를 첨가한 혼합액을 $37^{\circ}C$에서 4시간 반응시켰을 때 이며, 이 조건에서 유당이 약 94% 가수분해 되었고 생성된 oligosaccharides의 양은 총 당의 약 30% 이었다. 생성된 총 oligosaccharides의 69%는 $6-o-{\beta}-D-galactopyranosyl-D-glucose(allolactose)$, 23%는 $6-o-{\beta}-D-galactopyranosyl-D-galactose(isogalactobiose)$ 이었으며, 형성된 galactooligosaccharides을 Bio-Gel P-2 gel permeation chromatography 방법에 의해서 순수하게 분리 정제하여 구조를 조사하여 본 결과 glucose, galactose, allolactose, 그리고 isogalactobiose 임을 확인할 수 있었다.