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BACKGROUND: The organosolv process promotes biomass delignification at relatively high temperatures using a wide variety of organic solvent solutions. Nevertheless, previous studies on organosolv processes have not dealt with the use of ethyl lactate as organic solvent. Thus the aim of the present contribution was to determine and to validate if the use of ethyl lactate has a positive influence on lignin recovery for organosolv processes whose feedstock is the solid waste from a wheat straw‐based biorefinery. The effect of operating conditions (temperature and time) on lignin recovery was also studied. RESULTS: A mixed design of experiments was proposed as the strategy to maximize lignin recovery. The mathematical model derived from a multiple linear regression applied to the mixed design results indicates that 190 °C and a non‐aqueous solution containing ethyl lactate and ethanol (81.2% w/w ethyl lactate) could provide a maximum lignin recovery of 75.9% w/w. This theoretical maximum was validated. Thus the proposed model adequately describes the behavior of lignin recovery. Moreover, Fourier transform infrared (FTIR) characterization of the resultant lignin suggested that its structure is a function of the organic solvent solution used during the organosolv process. CONCLUSION: The evidence from this study indicates that lignin recovery from the solid waste of a wheat straw‐based biorefinery in an organosolv process depends on temperature and ethyl lactate presence in the reaction medium. These findings enhance the understanding of organosolv processes and could be applied if eventual lignin valorization is desired. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Mexico is one of the largest agricultural producers in Latin America and generates a large amount of agricultural residue. The aim of this study was to establish the usefulness of four of the main Mexican crops (corn, wheat, sugarcane, and Agave) as feedstock for lignocellulosic bioethanol production. The lignocellulosic residue ratio (RR), defined as weight of residue (in tons) per ton of product, was measured by sampling crop fields in 11 geographic regions of Mexico. The chemical composition, assessed by Fourier‐transform infrared spectroscopy (FTIR) and carbon‐13 nuclear magnetic resonance (13C NMR), and structural composition (extractives, cellulose, hemicellulose, and lignin contents), heating value, and metal content of these lignocellulosic residues were measured. Biorefinery locations, and their theoretical bioethanol production, were suggested using the gravity center method and techno‐economic criteria. The highest RR (1.1 ton of straw per ton of grain) was obtained for wheat straw followed by corn (0.8 ton of stover per ton of grain), sugar cane (0.15 ton of bagasse per ton of cane), and Agave (0.2 ton of bagasse per ton of stem). The composition of these biomasses varied significantly depending on the parental material in extractive compounds, lignocellulosic matter, ashes, hemicellulose, lignin, O‐alkyl C, aromatic C, and carboxyl C. The cellulose crystallinity index and the heating value exhibited small variations among biomasses. Copper, Zn, Cd, and Ni content in the biomasses generally exceeded the European Norm (EN‐Plus FprEN 1496 1‐2 B) for solid biofuels. In total, these agricultural biomasses could be used as feedstock for 34 biorefineries in Mexico with a total bioethanol production potential of approximately 1246 million L year–1. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Abstract: The changes occurring during the depolymerization of lignocellulosic biomasses are not yet fully understood. Synchrotron micro‐Fourier transform infrared (µ‐FTIR), Raman spectroscopy (RS), X‐ray diffraction (XRD), and X‐ray fluorescence (XRF) were applied for better characterization of wheat straw fibers during a continuous pretreatment process in terms of conditioning (C), extrusion (E), steam explosion (SE), and enzymatic hydrolysis (EH). µ‐FTIR revealed functional groups as phenylpropanoid polymers, ethers, and aliphatic alcohol. RS detected acetoacetate, methyl and phenol groups after SE. The crystallinity index and silica content were also determined. [ABSTRACT FROM AUTHOR]

This study reports the ability of Escherichia coli WDHL to metabolize pentoses commonly found in lignocellulosic hydrolysates to produce bioethanol (EtOH) and biohydrogen (H 2 ). A Central Composite experimental design was used to establish the effects of pH, temperature and total reducing sugars (TRS) from the wheat straw hydrolysate (WSH) on production, production rate and yield of bioethanol and biohydrogen. Optimal conditions for the simultaneous production were pH 8.2, 31 °C and 23.4 g TRS dm −3 . Batch culture was performed with these conditions in a 1 dm 3 bioreactors, obtaining: 8.9 g EtOH dm −3 , 0.050 g EtOH dm −3 h −1 , 0.38 g EtOH g TRS −1 , and 3277.7 cm 3 H 2 , 18 cm 3 H 2 dm −3 h −1 , 140.1 cm 3 H 2 g TRS −1 . The results showed that the pH and the temperature affected the production of both biofuels. This work enriches the information of simultaneous production of bioethanol and biohydrogen by using second-generation substrates. [ABSTRACT FROM AUTHOR]

Enhancing substrate accessibility is one of the prerequisites for efficient pretreatment and bioconversion of lignocellulosic biomass, for which reducing particle size and increasing porosity have been implemented. Biomass porosity, characterized as the water retention capacity (WRC), increases significantly with the use of a culture filtrate of an H 2 -producing microbial consortium, causing native lignocellulosic fibers to hydrate and swell extensively. This study describes the effects of hydration treatment and particle size on the biodegradability of native wheat straw fibers with regard to direct H 2 production by a microbial consortium. A culture filtrate and tap water were used as hydration media, and particle sizes of 0.212 and 3.35 mm were tested. As a result, biodegradability, measured as H 2 production, doubled when the lignocellulosic substrate was hydrated with the culture filtrate. Also, hydration had a significant impact on H 2 yield, increasing it from 6.8 to 86.5 mL H 2 /g total consumed sugars when the 0.212 mm fibers were first hydrated. H 2 production was higher with coarser particles (3.35 > 0.212 mm), but hydrogen yield improved with finer particles (0.212 > 3.35 mm). Based on our results, particle size and hydration improve the biodegradability of native wheat straw for H 2 production, although hydration with a culture filtrate increased the biomass porosity (measured as WRC), which influenced the biodegradability more than a reduction in particle size. [ABSTRACT FROM AUTHOR]

Hydrothermal pretreatment (HP) is an eco-friendly process for deconstructing lignocellulosic biomass (LCB) that plays a key role in ensuring the profitability of producing biofuels or bioproducts in a biorefinery. At the laboratory scale, HP is usually carried out under non-isothermal regimes with poor temperature control. In contrast, HP is usually carried out under isothermal conditions at the commercial scale. Consequently, significant discrepancies in the values of polysaccharide releases are found in the literature. Therefore, laboratory-scale HP data are not trustworthy if scale-up or retrofitting of HP at larger scales is required. This contribution presents the results of laboratory-scale batch HP for wheat straw in terms of xylan and glucan release that were obtained with rigorous temperature control under isothermal conditions during the reaction stage. The heating and cooling stages were carried out with fast rates (43 and −40 °C/min, respectively), minimizing non-isothermal reaction periods. Therefore, the polysaccharide release results can be associated exclusively with the isothermic reaction stage and can be considered as a reliable source of information for HP at commercial scales. The highest amount of xylan release was 4.8 g/L or 43% obtained at 180 °C and 20 min, while the glucan release exhibited a maximum of 1.2 g/L or 5.5%. at 160 °C/180 °C and 30 min. [ABSTRACT FROM AUTHOR]

Wheat straw is gaining importance as a feedstock for the production of biofuels and high value-added bioproducts. Several pretreatments recover the fermentable fraction involving the use of water or aqueous solutions. Therefore, hydration properties of wheat straw fibers play an important role in improving pretreatment performance. In this study, the water retention capacity (WRC) and swelling of wheat straw fibers were studied using water, propylene glycol (PPG) and an effluent from a H2-producing reactor as the hydration media with three particle sizes (3.35, 2.00 and 0.212 mm). The effects of swelling were analyzed by optical and confocal laser scanning microscopy (CLSM). The highest WRC was reached with the effluent medium (9.84 ± 0.87 g g−1 in 4 h), followed by PPG (8.52 ± 0.18 g g−1 in 1 h) and water (8.74 ± 0.76 g g−1 in 10 h). The effluent hydration treatment had a synergic effect between the enzymes present and the water. The particle size had a significant effect on the WRC (P < 0.01), the highest values were reached with 3.35 mm fibers. The CLSM images showed that finer fibers were subjected to a shaving effect due to the grinding affecting its capacity to absorb the hydration medium. The microscopic analysis showed the increase in the width of the epidermal cells after the hydration and a more undulating cell wall likely due to the hydration of the amorphous regions in the cellulose microfibrils. The sugar release was determined, achieving the highest glucose content with the effluent hydration treatment. [ABSTRACT FROM AUTHOR]

• BMP from discharged hydrothermally pretreated biomasses is presented. • Diauxic methane production was observed for sugarcane and corn wastes. • The highest BMP was obtained for the sugarcane and the lowest for agave bagasse. • A low biodegradability was found for corn straw, wheat straw, and agave wastes. • The liquid fraction produced higher BMP than the solid fraction. During the second-generation ethanol production, wastes from the hydrothermal pretreatment process are generated. Such rich organic matter residues should be treated. An alternative for that waste is methane production via the anaerobic digestion process. The characterization and the evaluation of the biochemical methane potential (BMP) and hydrolysis rates from the wasted hydrothermally pretreated wheat straw, corn straw, sugarcane, and agave bagasse was investigated. The liquid extracted lixiviates, and the solid fraction of each waste was evaluated. Diauxic methane production was observed for sugarcane and corn liquid fractions and for all the solids fractions. BMP varied from 369 mL CH 4 /g COD (sugarcane bagasse) to 178 mL CH 4 /g COD (agave bagasse). The biodegradability percentage was decreasing from sugarcane bagasse (100%), corn straw (65%), wheat straw (55%) and agave bagasse (51%). The liquid fraction produced higher BMP values than the BMP obtained for the solid fraction. The relatively low biodegradability of the hydrothermally pretreated wastes, considering the carbohydrate-rich nature of the substrate, was associated with an inhibitory effect. A double effect caused by the presence of furfural was observed. At lower concentrations, there was an inhibitory effect, while for the high concentration a stimulatory effect was detected. [ABSTRACT FROM AUTHOR]