Production, Refining, Structural Characterization and Fermentability of Rice Husk Xylooligosaccharides

Abstract

Oligosaccharides produced by hydrothermal processing of rice husks (xylooligosaccharides and glucooligosaccharides) were refined by membrane processing (operating in diafiltration and concentration modes), subjected to xylanase treatment to reduce the average molar mass, and subjected to further purification by ultrafiltration (operating in concentration mode) and ion exchange. The purified products were assayed for composition, molar mass distribution and structural characterization by HPLC, HPAEC-PAD, HPSEC, MALDI-TOF-MS and NMR ((1)H and (13)C). The fermentability of the purified product by fecal inocula was assessed on the basis of the time courses of pH and oligosaccharide concentrations. Succinate, lactate, formiate, acetate, propionate and butyrate were the major products resulting from fermentation experiments.

Prebiotic potential of a refined product containing pectic oligosaccharides

“…After 14 h, the molar ratio of acetate:propionate:butyrate in the fermentation media was 1:0.08:0.17. Similar molar ratios were reported in an earlier study on the fermentability of xylooligosaccharides obtained from rice husks (Gullón et al, 2010b). Fermentation times longer than 14 h resulted in depletion of lactate and succinate: both acids are intermediary products of carbohydrate fermentation, and can be converted into acetate, propionate and butyrate by common intestinal bacteria (Belenguer et al, 2006;Gullón et al, 2010b;Macfarlane & Macfarlane, 2003).…”

“…Faeces were collected into sterile vials, kept in an anaerobic cabinet and used within a maximum of 2 h after collection. Faecal inoculum (FI) was prepared by dilution in a reduced physiological salt solution (RPS; cysteine-HCl 0.5 g/L and NaCl 8.5 g/L) at a 100 g faeces/L RPS and pH 6.8, following the methodology described elsewhere (Gullón et al, 2010b).…”

“…A second sample of liquors was subjected to quantitative acid posthydrolysis (with 4 g sulfuric acid/100 g solution at 121 C for 20 min) before duplicate HPLC analysis. Glucooligosaccharides, galactooligosaccharides and xylooligosaccharides (measured in a single fraction, as galactose and xylose were eluted in one peak) and arabinooligosaccharides were determined by HPLC on the basis of the increase in sugar concentration caused by acid posthydrolysis of liquors (Gullón et al, 2010b). Uronic acids were determined by the method of Blumenkrantz and Asboe-Hansen (1973) using galacturonic acid as a standard for quantification.…”

Effects of hemicellulose-derived saccharides on behavior of Lactobacilli under simulated gastrointestinal conditions

“…Xylooligosaccharides (XOS) from E. globulus wood were obtained by consecutive stages of water extraction, autohydrolysis, membrane processing, anionic exchange and freeze drying following the method reported elsewhere (Gullón, González-Muñoz, van Gool, et al, 2011). XOS were manufactured from rice husks by autohydrolysis followed by membrane processing (diafiltration and concentration), enzymatic treatment with endoxylanases, anionic exchange and freeze drying (see Gullón et al, 2010). Wheat bran was subjected to water extraction, autohydrolysis, diafiltration-concentration, anionic and cationic exchange and freeze-drying according Gullón et al (2014).…”

“…Among them, a number of oligosaccharides derived from the hemicelluloses were evaluated as prebiotics using in vitro fermentation system with human fecal cultures, but only some features were considered, namely the effect of the consumption of substrates, the growth of target microbial groups and the subsequent generation of short chain fatty acids (Amaretti et al, 2012;Gullón et al, 2008Gullón et al, , 2010Rivas, Gullón, Gullón, Alonso, & Parajó, 2012;Wang, Sun, Cao, & Wang, 2010). Therefore, to our knowledge, the protective effects of hemicellulose-derived xylooligosaccharides on probiotic bacteria throughout gastrointestinal conditions have not been reported yet, and may be an important complementary property to be added to the others already validated previously.…”