46
et al. 2003). Zhu and Zhao (2013) reported that the concentration of SCFA increased
due to the fermentation of retrograded maize starch. In another study, an increasing
trend was observed in propionate, acetate and butyrate when rats were fed with high
amylose maize (RS3) (Charrier et al. 2013). Various in vitro studies confirmed the
diminished hydrolysis of starch or starch ingredients that had undergone chemical
or physical modification (b-cyclodextrinisation, acetylation, gelatinization etc.) to
small intestine hydrolysis depending on the rate of modification or the degree of
substitution. A study conducted by (Raben et al.) showed an immense enhancement
in large bowel SCFA production by feeding a group of rats with acetylated starches.
The probable mechanism involved production of esterified fatty acids and fermentation of the available starches. Furthermore, Kalmokoff et al. (2013) reported an
increase of propionate in rats fed with high amylose maize starch (RS2). Jenkins
et al. (1998) reported that 12 women and 12 men were fed diet with or without the
supplementation of 30 g high amylose starch (RS2) or retrograded high amylase
starch (RS3) daily for 2 weeks, followed by a 2 week washout intervals. It was
reported that butyrate concentration in the fecal water was increased in those persons who were fed with RS supplemented diet (mean of RS2 and RS3) (22.7 mmol/L)
in comparison to low fiber diet (19.2 mol/L). Martínez et al. (2010) studied the
effects of RS (RS2 and RS4) on the fecal microbiota in humans. In this study 10
human participants were fed with crackers supplemented with granular form of
high-amylose corn starch (RS2) or chemically modified by phosphate cross- linking
(RS4) for three weeks, which were compared with control starch in the form of
crackers. It was reported that both RS2 and RS4 significantly increased the
Actinobacteria and Bacteroidetesphyla and decreased Firmicutes. However both
forms of resistant starch differed in their ability to change species. It was further
reported that RS2 increased the number of Ruminococcusbromii and
Eubacteriumrectale, which is similar to previous results from in vitro studies of
starch fermentation in the large intestine (Kovatcheva-Datchary et al. 2009; Leitch
et al. 2007). In contrast, RS4 was linked with increased Bifidobacterium adolescentis and Parabacteroid esdistasonis (Martínez et al. 2010) (Fig. 1).
Recently, a number of studies have been conducted on the synergistic effects of
RS. In one such study it has been reported that the prebiotic effect of RS can be
increased by combining it with short chain fructooligosaccharides (FOS). This
combination has reportedly caused changes in the microbial flora of intestines by
increasing lactobacilli and bifidobacteria in caecum and colonic contents. These
observations have been confirmed in vivo once the different prebiotics reach the
large intestine: FOS are rapidly fermented, whereas RS is slowly degraded. In consequence, the particular kinetics would determine the region of the intestine where
the effects will be clearer. Thus, FOS would be more active in the first parts of the
large bowel whereas RS would reach the distal part of the colon (Rodríguez-Cabezas
et al. 2010; Fuentes-Zaragoza et al. 2010). Various studies conducted by different
researchers over different periods of time conclusively accomplished that RS serves
as a feeding substrate for Bifidobacterium under in vitro conditions and simultaneously can act as an efficient shield for protection of bacteria under in vivo conditions
while surpassing the gastrointestinal conditions (Wang et al 1999). Other in vitro
G. Akhtar et al.
et al. 2003). Zhu and Zhao (2013) reported that the concentration of SCFA increased
due to the fermentation of retrograded maize starch. In another study, an increasing
trend was observed in propionate, acetate and butyrate when rats were fed with high
amylose maize (RS3) (Charrier et al. 2013). Various in vitro studies confirmed the
diminished hydrolysis of starch or starch ingredients that had undergone chemical
or physical modification (b-cyclodextrinisation, acetylation, gelatinization etc.) to
small intestine hydrolysis depending on the rate of modification or the degree of
substitution. A study conducted by (Raben et al.) showed an immense enhancement
in large bowel SCFA production by feeding a group of rats with acetylated starches.
The probable mechanism involved production of esterified fatty acids and fermentation of the available starches. Furthermore, Kalmokoff et al. (2013) reported an
increase of propionate in rats fed with high amylose maize starch (RS2). Jenkins
et al. (1998) reported that 12 women and 12 men were fed diet with or without the
supplementation of 30 g high amylose starch (RS2) or retrograded high amylase
starch (RS3) daily for 2 weeks, followed by a 2 week washout intervals. It was
reported that butyrate concentration in the fecal water was increased in those persons who were fed with RS supplemented diet (mean of RS2 and RS3) (22.7 mmol/L)
in comparison to low fiber diet (19.2 mol/L). Martínez et al. (2010) studied the
effects of RS (RS2 and RS4) on the fecal microbiota in humans. In this study 10
human participants were fed with crackers supplemented with granular form of
high-amylose corn starch (RS2) or chemically modified by phosphate cross- linking
(RS4) for three weeks, which were compared with control starch in the form of
crackers. It was reported that both RS2 and RS4 significantly increased the
Actinobacteria and Bacteroidetesphyla and decreased Firmicutes. However both
forms of resistant starch differed in their ability to change species. It was further
reported that RS2 increased the number of Ruminococcusbromii and
Eubacteriumrectale, which is similar to previous results from in vitro studies of
starch fermentation in the large intestine (Kovatcheva-Datchary et al. 2009; Leitch
et al. 2007). In contrast, RS4 was linked with increased Bifidobacterium adolescentis and Parabacteroid esdistasonis (Martínez et al. 2010) (Fig. 1).
Recently, a number of studies have been conducted on the synergistic effects of
RS. In one such study it has been reported that the prebiotic effect of RS can be
increased by combining it with short chain fructooligosaccharides (FOS). This
combination has reportedly caused changes in the microbial flora of intestines by
increasing lactobacilli and bifidobacteria in caecum and colonic contents. These
observations have been confirmed in vivo once the different prebiotics reach the
large intestine: FOS are rapidly fermented, whereas RS is slowly degraded. In consequence, the particular kinetics would determine the region of the intestine where
the effects will be clearer. Thus, FOS would be more active in the first parts of the
large bowel whereas RS would reach the distal part of the colon (Rodríguez-Cabezas
et al. 2010; Fuentes-Zaragoza et al. 2010). Various studies conducted by different
researchers over different periods of time conclusively accomplished that RS serves
as a feeding substrate for Bifidobacterium under in vitro conditions and simultaneously can act as an efficient shield for protection of bacteria under in vivo conditions
while surpassing the gastrointestinal conditions (Wang et al 1999). Other in vitro
G. Akhtar et al.