In Vitro Assessment of the Prebiotic Potential of Xylooligosaccharides from Barley Straw

Barley straw was subjected to hydrothermal pretreatment (steam explosion) processing to evaluate its potential as a raw material to produce xylooligosaccharides (XOS) suitable for use as a prebiotic. The steam explosion pretreatment generated a liquid fraction containing solubilised hemicellulose. This fraction was purified using gel permeation chromatography to obtain a fraction rich in XOS DP2-DP6. The sample was characterised through analytical techniques such as HPAEC-PAD, FTIR and MALDI-TOF-MS. The prebiotic activity was evaluated using in vitro fermentation in human faecal cultures through the quantification of short-chain fatty acid (SCFA) and lactate production, the evolution of the pH and the consumption of carbon sources. The total SCFA production at the end of fermentation (30 h) was 90.1 mM. Positive significant differences between the amount of XOS from barley straw and fructooligosaccharides after incubation were observed.

Xylo-oligosaccharides, fermentable sugars, and bioenergy production from sugarcane straw using steam explosion pretreatment at pilot-scale

This study investigated the production of xylo-oligosaccharides (XOS) from sugarcane straw (SCS) using steam explosion (SE) pretreatment at pilot-scale, as well as co-production of fermentable sugars and lignin-rich residues for bioethanol and bioenergy, respectively. SE conditions 200 °C; 15 bar; 10 min led to 1) soluble XOS yields of up to 35 % (w/w) of initial xylan with ∼50 % of the recovered XOS corresponding to xylobiose and xylotriose, considered the most valuable sugars for prebiotic applications; 2) fermentable glucose yields from the enzymatic hydrolysis of SE-pretreated SCS of up to ∼78 %; 3) increase in the energy content of saccharified SCS residues (16 %) compared to the untreated material. From an integrated biorefinery perspective, it demonstrated the potential use of SCS for the production of value-added XOS ingredients as well as liquid and solid biofuel products.

Efficient production of nutraceuticals and lactic acid from lignocellulosic biomass by combining organosolv fractionation with enzymatic/fermentative routes

The aim of this work was to investigate the use of isobutanol as organic solvent for the efficient delignification and fractionation of beechwood through the OxiOrganosolv process in the absence of any catalyst. The results demonstrate that cellulose-rich solid pulp produced after pretreatment is a source of fermentable sugars that can be easily hydrolyzed and serve as a carbon source in microbial fermentations for the production of omega-3 fatty acids and D-lactic acid. The C5 sugars are recovered in the aqueous liquid fractions and comprise a fraction rich in xylo-oligosaccharides with prebiotic potential. The maximum production of optically pure D-lactic from Lactobacillus delbrueckii sp. bulgaricus reached 51.6 g/L (0.57 g/g_biomass), following a simultaneous saccharification and fermentation strategy. Crypthecodenium cohnii accumulated up to 52.1 wt% lipids with a DHA content of 54.1 %, while up to 43.3 % hemicellulose recovery in form of oligosaccharides was achieved in the liquid fraction.