BbgIV Is an Important Bifidobacterium β-Galactosidase for the Synthesis of Prebiotic Galactooligosaccharides at High Temperatures

The individual contributions of four beta-galactosidases present in Bifidobacterium bifidum NCIMB 41171 toward galactooligosaccharide (GOS) synthesis were investigated. Although the beta-galactosidase activity of the whole cells significantly dicreased as a function of temperature (40-75 degrees C), GOS yield was at its maximum at 65 degrees C. Native-PAGE of the whole cells showed that the contributions of BbgIII and BbgIV to GOS synthesis increased as the temperature increased. Moreover, BbgIII and BbgIV were found to be more temperature stable and to produce a higher GOS yield than BbgI and BbgII, when used in their free form. The COS yield using BbgIV was 54.8% (percent of total carbohydrates) and 63.9% (percent lactose converted to GOS) at 65 degrees C from 43% w/w lactose. It was shown that BbgIV is the most important beta-galactosidase in B. bifidum NCIMB 41121 and can be used for GOS synthesis at elevated temperatures.