Izaskun Dávila

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.

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.

The Biorefinery Concept for the Industrial Valorization of Grape Processing By-Products

The winemaking industry generates high amounts of underutilized by-products worldwide, which represent a significant economic potential and a great challenge. The main by-product of winemaking is grape marc, consisting of the stalks, skin, pulp (pomace), and seeds that remain after pressing the grapes. Other grape processing by-products include vine shoots (vine prunings), winery sludge (wine lees), effluents, and filtration residues. These residues have an interesting composition to be used as sources of high added-value products generated using environment friendly technologies within the biorefinery frame. Taking into account the problems induced by the disposal of these leftovers in the environment, this chapter describes the sustainable treatment of grape processing by-products within the integral biorefinery approach that promises potential economic benefits from the underutilized sources.

Hydrothermal treatment of chestnut shells (Castanea sativa) to produce oligosaccharides and antioxidant compounds

Hydrothermal treatment is an environmentally friendly technology that allows the solubilisation of hemicellulosic oligosaccharides with potential for their use as prebiotics. The purpose of this study was to solubilize oligosaccharides and antioxidant compounds from chestnut shells by a hydrothermal processing. The highest content of oligosaccharides (18.3 g/L), with a relatively low level of monosaccharides (2.4 g/L) and degradation products (0.5 g/L) was obtained at 180 °C (severity of 3.08). In addition, the liquors presented a high content of phenolic and flavonoid compounds with good antioxidant properties. The GC-MS revealed that the most abundant phenolic compound was pyrogallol (13.2%). The molecular weight distribution of the solubilization products showed that a 26.5% presented an apparent Mw of 6077 g/mol and a 73.5% presented an apparent Mw of 586 g/mol with a high polydispersity index. MALDI-TOF, FTIR, and TGA analyses revealed structural information of these compounds and their thermal stability.

Production and Emerging Applications of Bioactive Oligosaccharides from Biomass Hemicelluloses by Hydrothermal Processing

Hemicelluloses are the second most abundant heterogeneous polysaccharides in nature. Among the several treatments that can be used for the solubilization of hemicelluloses to produce oligosaccharides from lignocellulosic biomass, the autohydrolysis reaction is the most widely used. Under suitable conditions, autohydrolysis enables high ligosaccharides yields, however this reaction is not selective and undesired compounds are also present in the reaction media. Because of this, the autohydrolysis media has to be subjected to further processing to improve the purity of oligosaccharide hydrolysate. The chemical and structural characterization of the solubilized products from hemicelluloses is an important aspect as it allows to know the application for which they are more suitable. Oligosaccharides from hemicelluloses can find applications in several fields such as biomedical, food, and biomaterials.