Evaluation of strategies for second generation bioethanol production from fast growing biomass Paulownia within a biorefinery scheme

Applied Energy

http://dx.doi.org/10.1016/j.apenergy.2016.11.114

Fast-growing and short-rotation biomass is identified as glucan-rich feedstock to be used for bioenergy purposes. For the first time to our knowledge, fast growing biomass (Paulownia tomentosa) was evaluated for bioethanol production in a biorefinery scheme. For that, Paulownia wood was subjected to autohydrolysis pretreatment under severity (S0) conditions in the range of 3.31–5.16. The effect of this treatment on its fractionation was evaluated by means of hemicelluloses solubilization as hemicellulose-derived compounds in liquid phase and enzymatic hydrolysis of glucan (remained in the solid phase) into glucose. A xylose and xylooligosaccharides concentration of 17.5 g/L was obtained at S0 = 3.99 which corresponds to complete xylan solubilization. On the other hand, glucose yield of enzymatic hydrolysis increased up to reach 99% at S0 = 4.82. In addition, separate and simultaneous saccharification and fermentation assays (SHF and SSF) of autohydrolyzed Paulownia were compared for ethanol production. An increase of 47% in ethanol concentration was obtained by SHF in comparison with results achieved by SSF for Paulownia treated at S0 = 4.19. In SSF, Paulownia was successfully converted into ethanol (52.7 g/L which corresponded to 80% of ethanol yield) operating at 20% solid loadings and S0 = 4.72. Energy analysis of results obtained in this work showed that 83% of energy respect to raw material can be recovered considering the ethanol and the combustion of residual lignin. This work provides a feasible process for bioethanol production using fast growing specie which could enrich the feedstock needs for biofuels sector.

A biorefinery scheme for residual biomass using autohydrolysis and organosolv stages for oligomers and bioethanol production

Energy & Fuels

DOI: 10.1021/acs.energyfuels.6b00277

Straw is one of the main lignocellulosic waste produced during cereal crop cultivation. The abundance of barley straw makes it a good candidate for bioethanol production. This work deals with barley straw pretreatment by means of autohydrolysis in order to get xylooligosaccharides in the liquid phase, followed by an organosolv treatment using ethanol to increase the solid phase enzymatic susceptibility. Up to 17.4 g oligomers/L were obtained in the hydrothermal stage, in which practically all the cellulose and lignin remained in the solid phase. The solid phase from the hydrothermal-delignification was subjected to an experimental design in order to study the effect of pretreatment conditions in the bioethanol production, with values of solids concentrations in the range 7.7 to 20 weight % and values of enzyme loading in the range 14 FPU/g to 6 FPU/g. In the experiments carried out at a liquid to solid ratio = 4 g/g it is possible to obtain 31.6 g ethanol/L in just 9 h (corresponding to 100% ethanol conversion), with optimum results of 44.5 g ethanol/L in 46 h (90-93% glucose to ethanol conversion) and with a maximum concentration of 48.7 g ethanol/L in 89 h (79% conversion). The combination of a hydrothermal pretreatment (under conditions that lead to the recovery of high amounts of hemicellulosic by-products), followed by an organosolv treatment under mild conditions turns out to be suitable for second generation bioethanol production, applying a high solids loading, by means of fed-batch simultaneous saccharification and fermentation.

Combined alkali and hydrothermal pretreatments for oat straw valorization within a biorefinery concept

Bioresource Technology

http://dx.doi.org/10.1016/j.biortech.2016.08.077

The aim of this work was the evaluation of lime pretreatment combined or not with previous step of autohydrolysis for oat straw valorization. Under selected conditions of lime pretreatment, 96% of glucan and 77% of xylan were recovered and 42% of delignification was achieved. Xylose fermentation to ethanol by metabolic engineered Saccharomyces cerevisiae (MEC1133) strain improved the ethanol production by 22% achieving 41 g/L. Alternatively, first step of autohydrolysis (S0=4.22) allowed a high oligosaccharides recovery (68%) and subsequent lime pretreatment attained a 57% of delignification and 99% of glucan to glucose conversion. Oat straw processed by autohydrolysis and lime pretreatment reached the maximal ethanol concentration (50 g/L). Both strategies led to oat straw valorization into bioethanol, oligosaccharides and lignin indicating that these pretreatments are adequate as a first stage within an oat straw biorefinery.

Production and characterization of a novel distilled alcoholic beverage produced from blueberry (Vaccinium corymbosum L.)

Fruits, 2016, vol. 71(4), 215-220

http://dx.doi.org/10.1051/fruits/2016013

The cultivation of underutilized berries and the process production of high-value-added products, such as fruit-based spirits, could have a beneficial effect on the economy of disadvantaged rural mountain areas of Spain. However, production of a distilled alcoholic beverage from the blueberry has not been reported before. The pulp of blueberries var. Bluecrop was fermented with Saccharomyces cerevisiae IFI83, distilled by using a steam drag distillation system and the volatile compounds were determined by gas chromatography. In the distillate obtained, the mean concentrations of ethanol (45.3 mL 100 mL-1 distillate), volatile substances (317.1 g hL-1 absolute alcohol) and methanol (261.0 g hL-1 absolute alcohol) were in accordance with the specifications that the European Council (Regulation 110/2008) fixed for these compounds. In addition, the ratios [3-methyl-1-butanol/2-methyl-1-propanol] and [2-methyl-1-propanol/1-propanol] were 2.60 and 1.34, respectively, indicating that the distilled alcoholic beverage has a good organoleptic quality. The results suggest that blueberry can be successfully used for the production of a novel spirit with a good sensory quality that is safe for the consumers.

Production et caractérisation d’une nouvelle boisson alcoolisée distillée produite à partir de grande myrtille (Vaccinium corymbosum L.)

Fruits, 2016, vol. 71(4), 215-220

http://dx.doi.org/10.1051/fruits/2016013

La culture d’espèces de baies sous-utilisées et leur transformation en produits à haute valeur ajoutée, tels que les spiritueux à base de fruits, pourraient avoir un effet bénéfique sur l’économie des régions rurales et défavorisées des montagnes d’Espagne. La production d’une boisson alcoolisée distillée à partir de grandes myrtilles ou bleuets n’a pourtant jamais été signalée auparavant. La pâte de bleuet var. Bluecrop fermentée avec Saccharomyces cerevisiae IFI83, a été distillée en utilisant un système de distillation par train de vapeur d’eau; les composés volatils ont été déterminés par chromatographie en phase gazeuse. Dans le distillat obtenu, les concentrations moyennes d’éthanol (45,3 mL 100 mL-1 distillat), de substances volatiles (317,1 g hL-1 alcool absolu, aa) et de méthanol (261,0 g hL-1 aa) étaient conformes aux spécifications que le Conseil européen (règlement 110/2008) fixe pour ces composés. De plus, les rapports [3-méthyl-1-butanol/2-méthyl-1-propanol] et [2-méthyl-1-propanol/1-propanol] ont été de 2,60 et 1,34, respectivement, indiquant que la boisson alcoolisée distillée a une bonne qualité organoleptique. Les résultats suggèrent que la grande myrtille peut être utilisée avec succès pour la production d’un nouveau spiritueux de bonne qualité organoleptique et sanitaire pour les consommateurs.

Agricultural residue valorization using a hydrothermal process for second generation bioethanol and oligosaccharides production

Bioresource Technology, 191, 263-270 (2015)

DOI: 10.1016/j.biortech.2015.05.035

In the present work, the hydrothermal valorization of an abundant agricultural residue has been studied in order to look for high added value applications by means of hydrothermal pretreatment followed by fed-batch simultaneous saccharification and fermentation, to obtain oligomers and sugars from autohydrolysis liquors and bioethanol from the solid phase. Non-isothermal autohydrolysis was applied to barley straw, leading to a solid phase with about a 90% of glucan and lignin and a liquid phase with up to 168gkg-1 raw material valuable hemicellulose-derived compounds. The solid phase showed a high enzymatic susceptibility (up to 95%). It was employed in the optimization study of the fed-batch simultaneous saccharification and fermentation, carried out at high solids loading, led up to 52gethanol/L (6.5% v/v). 

Biomass, sugar, and bioethanol potential of sweet corn

GCB Bioenergy, 7, 153-160 (2015)

DOI: 10.1111/gcbb.12136

Sweet corn is a widely distributed crop that generates agricultural waste without significant commercial value. In this study, we show that sweet corn varieties produce large amounts of residual biomass (10 t ha-1) with high content of soluble sugars (25% of dry matter) in a short growing season (3 months). The potential ethanol production from structural and soluble sugars extracted from sweet corn stover reached up to 4400 l ha-1 in the most productive hybrids, 33% of which (1500 l ha-1) were obtained by direct fermentation of free sugars. We found wide genetic variation for biomass yield and soluble sugars content suggesting that those traits can be included as complementary traits in sweet corn breeding programs. Dual-purpose sweet corn hybrids can have an added value for the farmers contributing to energy generation without affecting food supply or the environment.