Evaluation of different resistant starch types for stimulating growth of the dominant lactic acid bacteria inhabiting human colon

Abstract

Resistant starch (RS) refers to the portion of starch and starch products that resistant to digestion as it passes through the digestive system. The RS is subdivided into four types depending on its chemical structure: RS1 (physically inaccessible starch), RS2 (resistant granular starch), RS3 (retrograded starch), and RS4 (chemically modified starch), and considered as prebiotics that can be a supplement to the diet, leading to the growth stimulation of probiotics bacteria and the increase in intestinal concentrations of lactic acid and short-chain fatty acids (SCFA) assumed to promote host health. The aim of this study was to evaluate the activities of beneficial gut micro-flora isolated from human feces on three types of RS (RS2, RS3 and RS4). Two isolates of lactic acid bacteria were obtained from fecal sample of healthy people at 20-40 years old, and performed their very good growth in the medium containing 1% of either RS2, RS3, RS4, or fructo-oligosaccharides (FOS), a standard prebiotic, as carbon sources. All carbon substrates were treated through the digestive model system. The bacterial growth and pH changes were monitored, and fermentation products were determined. The growth of both bacterial isolates in the provided substrates at 20 hour cultivation reached to the maximum of 10^10 CFU/mL. The highest content of lactic acid, 10,410 ppm, was determined in the fermentation of glucose by Lactobacillus sp. RCF10. RS3 was served as the best substrate for producing SCFA compared to RS4, RS2, and FOS, respectively. The highest content of SCFA was butyric acid, 11,575 ppm, which was higher than propionic and acetic acids. RS3 reveals the promising cheap prebiotic beneficial to human health.