Manufacture and Prebiotic Potential of Xylooligosaccharides Derived From Eucalyptus nitens Wood

Beatriz Míguez,José Luis Alonso,Carlos Vila,Patricia Gullón,Malén Massot-Cladera,Tomás Cotos-Yáñez,Francisco José Pérez-Cano

doi:10.3389/fceng.2021.670440

Abstract

Mixtures of xylooligosaccharides (XOS) were manufactured from Eucalyptus nitens samples by hydrothermal processing. In order to obtain a product suitable to be used as a prebiotic, the liquors obtained were subjected to a refining sequence consisting of a two-step membrane filtration followed by anion exchange and freeze-drying. The process proposed allowed to obtain a highly refined product mainly made up of a mixture of substituted XOS with a degree of polymerization, DP3–10, which was evaluated for its prebiotic potential by in vitro fermentation assays. Their effects on the microbiota composition and the metabolic activity were assessed along the fermentation time and compared to fructooligosaccharides (FOS, a gold standard prebiotic), using fecal inocula from donors belonging to two age-groups (young and elderly). Significant and similar increases were observed in most of the bacterial groups considered (including Bifidobacterium spp. or several butyrate-producers) in both XOS and FOS in vitro interventions, although XOS resulted in significantly higher increases in total bacteria and lower rises in Clostridium clusters I and II than FOS. Regarding the metabolic activity, higher amounts of total organic acid (TOA; 150 vs. 110 mM) and higher total short-chain fatty acid (SCFA)/TOA ratio (0.88 vs. 0.70 mol/mol) were achieved at 28 h using XOS as a carbon source in comparison with FOS. Moreover, both substrates resulted in different metabolite profiles. Higher percentages of acetate and propionate were achieved when XOS were used as substrates, whereas FOS resulted in slightly higher concentrations of butyrate. No differences were found between both age-groups. Taking together these results, it can be concluded that XOS produced from E. nitens by a biorefinery-based approach led to, at least, similar prebiotic activity as that observed with FOS.

Highlights

Even though the premise “we are what we eat” has been accepted around the world for more than 100 years, it only became an empirically demonstrated fact some decades ago because of the latest scientific advances in nutritional research
High-Performance Liquid Chromatography Aliquots of liquid streams A, B, D, and F were filtered through 0.45-μm cellulose acetate filters and analyzed by high-performance liquid chromatography (HPLC) (Agilent 1,200 series, Agilent, Waldbronn, Germany) to determine monosaccharides, galacturonyl substituents, and acetic acid and to evaluate the presence of sugar degradation products using an Aminex HPX-87H column working at 50◦C, a H2SO4 3 mM solution as mobile phase and a refractive index (RI) detector for the analyte identification. Another aliquot of each stream was subjected to a posthydrolysis with a 4% of H2SO4 at 121◦C for 30 min, and the resulting hydrolysate was analyzed by HPLC as described above
Samples of E. nitens wood were characterized according to the standard protocols as those employed by Penín et al (2019b)

Summary

Introduction

Even though the premise “we are what we eat” has been accepted around the world for more than 100 years, it only became an empirically demonstrated fact some decades ago because of the latest scientific advances in nutritional research. New Prebiotics From Eucalyptus nitens impact on both human health and overall well-being (Albenberg and Wu, 2014; Voreades et al, 2014; Sonnenburg and Bäckhed, 2016) In view of these facts, several scientific efforts have been focused on studying diet as a potential tool for gut microbiota modulation aiming the host health improvement (Moles and Otaegui, 2020; Myhrstad et al, 2020). Xylooligosaccharides (XOS) are prebiotic candidates made up of D-xylopyranosyl units (Dxylose) bounded through β(1→ 4)-xylosidic linkages that can include side chain substituents, such as arabinose, uronic acids, phenolic acids, and acetyl or methyl groups (Samanta et al, 2015) These oligomers can be manufactured from several biomass sources by using chemical and/or enzymatic technologies, followed by a sequence of fractionation and/or purification stages including membrane filtration, enzymatic tailoring, or ion exchange (Vázquez et al, 2000; Samanta et al, 2015; Poletto et al, 2020; Santibáñez et al, 2021). Both raw material and manufacture technology can affect the XOS composition and structure, their effects on the gut microbiota and its metabolic activity (Samanta et al, 2015; Karlsson et al, 2018)

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