Degradation of cell wall material of apple and wheat bran by human faecal bacteria in vitro

Abstract

A B S T R A C TThe effect of the structures of plant cell walls and their component polymers on the degradability of dietary fibre by bacteria of the human colon was investigated by inoculating culture media containing cell wall materials of apple and wheat bran with slurries of human faeces which were then incubated for periods of up to 72 h. In the apple substrates the amounts of pectic polysaccharides were extensively depleted afer 12 h, and afer 24 h over 90% of the initial carbohydrate had been degraded. Material which remained afer incubation was probably comprised of highly branched fragments of rhamnogalacturonans, cross-linked by phenolics and proteins, highly branched fragments of cross-linked xyloglucans, and degraded cellulose. In wheat bran the aleurone layer was preferentially degraded, but the glucuronoarabinoxylans, which were cross-linked by phenolic groups, and the lignified outer layers of the bran were very resistant to attack. Bacteria adhered mainly to the broken or damaged surfaces of the plant cell walls, and in the more resistant tissues only penetrated the intercellular regions.

Prebiotic potential of a refined product containing pectic oligosaccharides

“…After 32 h of fermentation, OGaU were quantitatively metabolized, resulting in an increased SCFA concentration, whereas pH remained fairly constant at 5.07. This finding is in agreement with literature data, which reported and extensive degradation of oligogalacturonides by colonic bacteria (Stevens, Selvendran, Bayliss, & Turner, 1988).…”

Effect of the Dietary Supplementation of Corn Hemicellulose on Fecal Flora and Bacterial Enzyme Activities in Human Adults

“…9 ) With an in vitro study, wheat bran hemicellulose, which has a similar structure to corn hemicellulose, was shown to be highly resistant to bacterial attack. 18 ) Corn hemicellulose was also resistant to degradation by several xylanases in vitro. Increased fecal weight leads to the dilution of many harmful compounds in the large intestine, and a reduction of the gastrointestinal transit time.…”

“…Nine healthy volunteers (seven males and two females, 26-43 years old) consumed their normal Japanese style of diet (the average DF intake was 18 caloric content was about 2,400 kcal and caloric percentage of fat was 27%). Throughout the experimental period, the daily diet of each subject was recorded, None of the subjects were given corn hemicellulose for 10 days.…”

Structure, physicochemical properties and in vitro fermentation of enzymatically degraded cell wall materials from apples

“…Stevens et al [43] found that (linear) pectins, arabinans and galactans were readily degraded by bacteria of the human colon whereas the highly branched rhamnogalacturonans, xyloglucans and especially cellulose were fermented later. An effective substrate for the production of high levels of butyrate is resistant starch [44].…”