Impact of carbohydrates on autoinducer-2 secretion of Bifidobacterium longum subsp. longum BBMN68.

In this study, the regularity of autoinducer-2 (AI-2) secretion during growth and the effect of the addition of various carbohydrates on AI-2 secretion in Bifidobacterium longum subsp. longum BBMN68 were investigated. The results indicated that the AI-2 concentration reached its highest level (2536·60 nmol l-1 ) at the early stationary growth phase, and then decreased to 1263·72 nmol l-1 at the late stationary growth phase in Bifidobacterium cultures. When the density of the cultures which mannose, fructose, sucrose and lactose had been added to reached an OD600 nm of 1·0, the AI-2 concentrations in the cultures were 1953·84, 1637·34, 1200·99 and 1077·60 nmol l-1 , respectively. These concentrations were all significantly higher than that of the control culture (1031·33 nmol l-1 ). Similarly, the addition of fructooligosaccharide significantly increased the AI-2 concentrations to 2094·29 nmol l-1 . This study provides the advanced evidence that certain carbohydrates promote the secretion of AI-2, and that this occurs at the single cell level and is therefore unaffected by cell density. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provided the advanced data of the regularity of autoinducer-2 (AI-2) secretion during growth and the promotion on AI-2 secretion of different added carbohydrates in Bifidobacterium, which may be a new potential strategy to improve the acid resistance of Bifidobacterium applied in the food industry.