Comparative fermentation of insoluble carbohydrates in an in vitro human feces model spiked with Lactobacillus acidophilus NCFM

Abstract

Dietary fiber and slow carbohydrates can have differential beneficial effects on gut microbial composition and metabolism. Insoluble substrates such as RS cannot be used in continuous simulation systems and we tested an in vitro batch fermentation system for possible prebiotic effects using waxy maize starch granules, pectin‐rich potato fiber, and potato lintner starch tested with human fresh fecal microbiota spiked with the probiotic Lactobacillus acidophilus NCFM. Microbial quantification by real‐time polymerase chain‐reaction (qRT‐PCR) revealed that Bacteroidetes was specifically suppressed by each insoluble carbohydrate resulting in a clear decrease in the ratio of Bacteroidetes and Firmicutes. Notably, all carbohydrates tested appeared to block the formation of the potentially harmful branched chain fatty acids (BCFA) fermentation products, but supported lactobacilli growth and increase in lactic acid production. Potato lintner starch had the greatest effect. Insoluble carbohydrates also suppressed production of SCFAs as compared to the control medium. Importantly, potato lintner starch most efficiently suppressed the ratio between the Bacteroidetes and Firmicutes and suppressed growth of bifidobacteria, Enterobactericeae and Faecalibacterium prausnizii. Degradative resistance of the lintner starch were linked to these effects. Problems using continuous fermentation systems for insoluble prebiotics and interpretation of batch fermentation data are discussed.

Slowly Digestible‐ and Non‐Digestible α‐Glucans: An Enzymatic Approach to Starch Modification and Nutritional Effects

“…Third, it can have an effect on the immune system . The two most prevalent probiotics are lactobacilli and bifidobacteria, both having optimal capabilities to use α‐glucans as substrate . Lactobacilli are naturally found in many food and agricultural products such as dairy products, pickle vegetable, silage, etc., and they are strictly fermentative, anaerobic and acidophilic.…”

Impact of Resistant Maltodextrins and Resistant Starch on Human Gut Microbiota and Organic Acids Production

“…Among these, bifidobacteria and lactobacilli are the dominant probiotics. These also have optimal capabilities to use α‐glucans as a substrate . Moreover, these populations tend to decrease in the human colon with age suggesting specific nutritional measures to be taken among the elderly population.…”

“…There are specific links between the colonic microbial fermentation of prebiotics; specific species of lactobacilli preferentially ferments short‐chain RMD while bifidobacteria preferentially ferments longer‐chain RMD yielding SCFAs . Likewise, comparing insoluble fiber including resistant starch and potato fiber was demonstrated to be efficient for production of lactic acid but not SCFA. This was associated with suppressed Bacteroidetes and stimulated Firmicutes, likely involved in suppression of type 2 diabetes and obesity subjects.…”

Recent insight in α-glucan metabolism in probiotic bacteria

“…Interestingly, α-1,6-gluco-oligosaccharides possess prebiotic potential as judged by preferential stimulation of probiotic bacteria and improved bowel function (Kaneko et al 1994, Yen et al 2011. Additionally, a recent report suggests that RS resulted in significant increase in lactic acid production and a change in the Bacteroidetes/Firmicutes ratio in fecal in vitro fermentations, supplemented with the probiotic strain Lactobacillus acidophilus NCFM (Knudsen et al 2013). These data are consistent with the importance of α-glucan metabolism in probiotic bacteria, which is also reflected by the notably high representation of glycoside hydrolase (GH) family 13 genes that are pivotal in α-glucan metabolism by probiotic bacteria as compared to other GH families according to the mechanism and sequence-based Carbohydrate-Active enZymes (CAZy) classification system (http://www.cazy.org/) (Cantarel et al 2009).…”