Fructans with Varying Degree of Polymerization Enhance the Selective Growth of _Bifidobacterium animalis_ subsp. _Iactis_ BB-12 in the Human Gut Microbiome In Vitro  
[PERSON]  
1 ProDigest BV, Technologiepark 82, 9052 Ghent, Belgium; pieter. dermatitis [6], reduced colon cancer risk [7], improvement of serum lipid levels and supporting weight loss in obese individuals [8; 9]. A crucial remark regarding synbiotics is that when a prebiotic substrate would be combined with a randomly selected probiotic, this prebiotic would not necessarily support the growth of the added probiotic [10]. Therefore, it is of importance that the prebiotic supports growth of the co-administered probiotic, thus resulting in more predictable and beneficial outcomes of the prebiotic [10; 11]. Fructan-type carbohydrates have been widely as prebiotic component in symbiotic formulations [12]. They occur naturally in many plant-based foods, such as chicory, asparagus and leek, and consist of \(\beta\)-(2,1)-linked fructose molecules with a terminal glucose moiety. Fractans are classified by their degree of polymerization (DP), with molecules with a DP ranging from 2 to 10 being classified as oligofructose (OF), while long-chain fuctans are termed inulin (IN) which is characterized by a DP \(\geq\) 10 up to a DP of 60 [13]. Fructan-type carbohydrates escape digestion in the upper gastrointestinal tract and reach the colon where they are fermented by the indigenous microbiota, including health-related _Bifidobacterium_ sp. [14]. A commercially available probiotic belonging to the _Bifidobacteriaceae_ family that is extensively used in functional foods and dietary supplements is _Bifidobacterium animalis_ subsp. _lactis_ BB-12. Several health benefits have been attributed to BB-12 intake, including hypocholesterolem effects [15], improvement of bowel function [16], protection against diarrhea [17] and immunomodulation [18]. As BB-12 is able to ferment fructan-type carbohydrates [19], it has a potential to be combined with fructans as a symbiotic combination. Previously, [PERSON] et al. demonstrated in BB-12 monocultures that fructan structure affects its fermentation by BB-12 [20]. Therefore, the effectiveness of a fructan-based symbiotic with BB-12 might highly depend on the structure of the selected fructan. Next, when assessing the potential of a prebiotic to support growth of a probiotic, it is important to consider that the human colon is colonized by a dense microbial community that has as its key function the fermentation of both host and diet-derived carbohydrates [21]. The human colon microbiota thus has a large potential to ferment prebiotics such as fructans. When evaluating the potential fermentation of a prebiotic by a probiotic strain, it is thus important to not only address this research question in monocultures of the probiotic but also to assess this in presence of a (simulated) colon microbiota. Furthermore, given the existence of interindividual differences in microbiome composition among human individuals, mainly caused by genetic background and diet [22], interactions between the probiotic and the indigenous microbiota can differ among donors as for instance demonstrated by the interindividual differences in microbiome modulation upon fructant treatment [23; 24; 25]. Furthermore, also colonization of probiotics such as BB-12 could depend on interindividual differences as shown by [PERSON] et al. [26]. The present study aimed to identify which fructan-type carbohydrates supported growth of the probiotic strain BB-12 most optimally, both in BB-12 monocultures as well as during short-term colonic incubations in presence of a mixed microbiota derived from multiple healthy human donors. The study was conducted in three stages (Figure 1). First, potential fermentation of seven different fructan-type carbohydrates by BB-12 was investigated in monoculture incubations with focus on growth of BB-12 (as detected via qPCR) and its resulting metabolic activity (experiment 1).