Patricia Gullón

Assessment on the fermentability of xylooligosaccharides from rice husks by probiotic bacteria.

Liquors from rice husk autohydrolysis, containing xylooligosaccharides (XOS), other saccharides, and nonsaccharide compounds, were refined by membrane processing to increase the proportion of substituted XOS in refined liquors. XOS were assayed for composition and degree of polymerization (DP) distribution and hydrolyzed with commercial enzymes for obtaining XOS with DP in the range of 2-6. Nanofiltered, hydrolyzed liquors were subjected to ion exchange processing to yield a final product containing monosaccharides, XOS (accounting for 55.6% of the nonvolatile solutes), and other nonvolatile compounds. The solution obtained after enzymatic hydrolysis with commercial xylanases (in which 82.8% of XOS were in the DP range of 2-6) was examined as a medium for promoting the growth of Bifidobacterium adolescentis CECT 5781, B. longum CECT 4503, B. infantis CECT 4551, and B. breve CECT 4839. The growth rate of B. adolescentis (0.58 h(-1)) was higher than the ones determined for B. longum, B. infantis, and B. breve (0.37, 0.30, and 0.40 h(-1), respectively). The percentage of total XOS consumption by B. adolescentis was 77% after 24 h, the highest percentage of utilization corresponding to xylotriose (90%), followed by xylobiose (84%), xylotetraose (83%), and xylopentaose (71%).

Manufacture and prebiotic potential of oligosaccharides derived from industrial solid wastes

The solid waste obtained in malting industries when dehulling barley grains, which was mainly made up of barley husks, spent grains and grain fragments, was subjected to a double hydrothermal processing under selected conditions. The liquor from the second stage (containing xylooligosaccharides, XOS) was refined by membrane and ion exchange processing (with or without a previous endoxylanase treatment to reduce the XOS molecular weight). Three XOS concentrates with different purity and/or molecular weight distribution were fermented in vitro with faecal inocula to assess their prebiotic potential. Succinate, lactate, formiate, acetate, propionate and butyrate were generated in fermentations, confirming the prebiotic potential of the various products assayed. The purity of XOS concentrates did not play a significant role in fermentation, whereas the sample with shorter average degree of polymerization presented a faster fermentation kinetics and led to the highest concentration of lactic acid.

Brazilian fruit pulps as functional foods and additives: Evaluation of bioactive compounds

Eight tropical fruit pulps from Brazil were simultaneously characterised in terms of their antioxidant and antimicrobial properties. Antioxidant activity was screened by DPPH radical scavenging activity (126-3987 mg TE/100g DW) and ferric reduction activity power (368-20819 mg AAE/100g DW), and complemented with total phenolic content (329-12466 mg GAE/100g DW) and total flavonoid content measurements (46-672 mg EE /100g DW), whereas antimicrobial activity was tested against the most frequently found food pathogens. Acerola and açaí presented the highest values for the antioxidant-related measurements. Direct correlations between these measurements could be observed for some of the fruits. Tamarind exhibited the broadest antimicrobial potential, having revealed growth inhibition of Pseudomonas aeruginosa. Escherichia coli, Listeria monocytogenes, Salmonella sp. and Staphylococcus aureus. Açaí and tamarind extracts presented an inverse relationship between antibacterial and antioxidant activities, and therefore, the antibacterial activity cannot be attributed (only) to phenolic compounds.

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

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.

Manufacture and Properties of Bifidogenic Saccharides Derived from Wood Mannan

Pinus pinaster wood samples were subjected to double hydrothermal processing. The liquors coming from the second stage, containing soluble saccharides of polymeric or oligomeric nature from hemicelluloses (POHs), were subjected to membrane processing (operating in discontinuous diafiltration) for refining and fractionation. Refined POH fractions were characterized by matrix-assisted laser desorption/ionization time of flight mass spectrometry and chromatographic techniques. The most complex POH component was made up of 14 hexoses and contained 4 acetyl groups. The fermentability of purified POHs by human fecal inocula was assessed by measuring both carbon source consumption and formation of short-chain fatty acids. The bifidogenic ability of POHs was confirmed by fluorescence in situ hybridization. The stimulatory effects on the bifidobacterial population reached by POHs were of the same order as those obtained with commercial fructooligosaccharides.

Assessment of suitability of vine shoots for hemicellulosic oligosaccharides production through aqueous processing.

Vine shoots were subjected to non-isothermal aqueous processing. A range of severities (S0) from 3.20 to 4.65 was assayed and their effects in terms of solubilization, composition, molar mass distribution, structural characterization and thermal stability of the liquors were studied using HPLC, HPSEC, TGA and FTIR. The spent solids were characterized by HPLC and FTIR. When autohydrolysis was carried out at S0=4.01, the substrate solubilization achieved a 38.7% of the raw material and 83.1% of the initial xylan was converted into xylooligosaccharides (XOS). The amount of TOS (total oligosaccharides) in the hydrolysates was 28.4g/L while the other non volatile compounds (ONVC) were 0.08g/g NVC. The spent solid from the treatment at S0=4.01 was composed about 90% of cellulose and lignin. Therefore, it can be concluded that autohydrolysis is a suitable pretreatment of vine shoots such as a first stage of a biomass refinery.

Selected Process Alternatives for Biomass Refining: A Review

The role of biorefineries in the production of energy and chemicals from biomass of lignocellulosic nature is reviewed. Special attention is devoted to biorefinery schemes dealing with the fractionation of lignocellulosic raw materi- als by chemical treatments. The potential of hydrothermal treatments as the first stage of future biorefineries is discussed. Special attention is devoted to the low-volume, high-added value products that can be solubilized by this type of technol- ogy.

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

Four types of purified xylooligosaccharides (XOS) from several lignocellulosic materials, showing different structural features (including chain length, branching, and linkage types), obtained from different feedstocks (Eucalyptus globulus wood, rice husks, wheat bran or barley wastes), were assessed (using fructooligosaccharides as reference substrate) for their effects on the growth of six different probiotic Lactobacillus strains in basal MRS media and survival in different simulated gastrointestinal tract (GIT) conditions. The hydrophobicity of bacterial cells, which measures their potential for epithelial adhesion, was also evaluated. Improved growth of Lactobacillus strains was observed for media containing XOS as the single source of carbohydrate, confirming their role as prebiotics. These oligosaccharides also led to improvement in the resistance of the target Lactobacillus to the simulated GIT environment. The enhancement of the survival rates depended on the type of oligosaccharide. This is the first comparative study of the effects in lactobacilli involving four types of XOS obtained from different lignocellulosic materials. The obtained results show that these oligosaccharides manufactured from alternative sources could be interesting prebiotic substrates with different structures in comparison with the available commercially and with interesting potential towards the development of synbiotic products.

Coproduction of lignin and glucose from vine shoots by eco-friendly strategies: Toward the development of an integrated biorefinery

The objective of this work was to study the suitability of the pretreated vine shoots as a source of lignin and to determine its structural features. The best conditions to achieve the aim of this work were 12% NaOH, 124°C and 105min, as they permitted a removal of 67.7% of the lignin present in the pretreated vine shoots and the obtaining of a solid with a 69.4% of glucan. This delignified solid was subjected to an enzymatic hydrolysis achieving a conversion of glucan to glucose close to 100%. The characterization of lignins extracted from pretreated vine shoots was carried out for the first time and the following techniques were employed: a quantitative acid hydrolysis, HPSEC, TGA, FTIR and Pyrolysis-GC/MS. With this proposal, products from the main fractions of the vine shoots (hemicellulosic oligosaccharides, lignin fragments and cellulosic substrates) could be obtained separately, being potentially suitable for further applications.

Comparative environmental Life Cycle Assessment of integral revalorization of vine shoots from a biorefinery perspective

The use of vine shoots as feedstock in biorefining activities to obtain bioproducts under efficient and optimized conditions could be crucial to make future high added value compounds and processes more sustainable. In this study, five different potential valorization scenarios from vine shoots differing on diverse extraction and delignification steps were assessed from an environmental perspective using the Life Cycle Assessment methodology to identify the most sustainable biorefining route. The main findings from this study reported that an increment on the number of valorization steps involved higher energy and chemical requirements deriving on worse environmental profiles. Scenarios incorporating fermentation of the glucose liquors or organosolv delignification performed the worst profiles. Autohydrolysis, concentration and freeze drying and enzymatic hydrolysis were the main responsible stages of the environmental burdens. Further research should be focused on optimizing chemicals and electricity requirements to develop greener systems.