In vitro investigation of orange fleshed sweet potato prebiotic potential and its implication on human gut health
Background: Some food ingredients (prebiotics) have been shown to promote a healthy gut by selectively stimulating growth/activity of beneficial gastrointestinal microbes and metabolites such as short chain fatty acids (SCFA) while inhibiting pathogens. Orange fleshed sweet potato (Ipomoea batatas Lam; OFSP) root tuber is a starchy tropical crop and highly nutritious in terms of pro-vitamin A (beta carotene), dietary fibre, and natural sugars, with negligible amount of fats and cholesterol.
Purpose of study: The aim of the study was to investigate using simulated human gut system whether OFSP may have prebiotic activity derived from their fibre, resistant starch, and/or the sugars.
Methodology: In vitro pH controlled stirred batch culture fermentation system was used to compare the effect on human gut microbiota of four substrates: two varieties of OFSP (SPK 004 and Tainung), FOS and sucrose known for positive prebiotic and non-selective change respectively. The system was inoculated with faecal slurry from six different human healthy donors from different ethical backgrounds, age, and the effectual change recorded over 24 hours by monitoring bacterial counts (total bacteria, Bacteroides and Bifidobacterium) using qPCR molecular technique and SCFA profiles by gas chromatography.
Results: The total bacteria count increased by (0.92-1.7 log10) and Bacteroides genus (1.03-1.8 log10) throughout the experimental period but with no significant differences (p<0.05) between the four substrates. However, there were significant differences (p<0.05) in the beneficial Bifidobacterium (1.66-2.66 log10) between the 2 varieties of OFSP and the two controls (FOS and sucrose). The levels of SCFA increased, with acetate as the predominant acid and lactic acid being the least. The OFSP purees elicited high butyric acid levels, which were comparable to those of positive control FOS.
Conclusions: The study demonstrated that OFSP purees may have prebiotic potential that can positively modulate gut microbiota by promoting growth of beneficial bacteria, bifidobacterium genus, and stimulating production of SCFA especially butyric acid which is the favourable in human gut health. However, further research using more probiotic and pathogenic microbes in addition to in vivo clinical studies and compositional analysis of OFSP is needed to confirm prebiotic activity.
Key words: Orange fleshed sweet potato, prebiotic, human gut microbiota
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Copyright (c) 2017 Mary Muchiri, Anne L. McCartney