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The present work investigates the impact of the physical properties and loading strategies of wheat straw and miscanthus on enzymatic hydrolysis at high DM concentration. Three parameters have been chosen to evaluate the enzymatic hydrolysis performance: (i) the mixing time, (ii) the energetic mixing consumption and (iii) the glucose concentration. It was demonstrated that the hydrolysis of miscanthus is easy to perform and has low viscosity. On the contrary, the higher porosity grade of wheat straw than miscanthus (73% against 52%) contributed to have a very high viscosity at 20% w/w DM. The development of a fed-batch strategy allowed the reduction of viscosity inducing the energetic consumption lowering from 30 kJ to 10 kJ. It has been also proven that the miscanthus addition in wheat straw achieved to decrease mixing energy consumption at 5-8 kJ, when it represented more than 30% of the total mass of the reaction medium., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

After acidic and high-temperature pretreatment of lignocellulosic biomass, researchers find that some lignin-like substance appeared on the surface of cellulose, which is called pseudo-lignin. Pseudo-lignin can be formed through carbohydrate degradation or substitution reactions on the aromatic ring of lignin. Pseudo-lignin is identified as Klason lignin in compositional analysis, whereas in Py-GC-MS analysis, it is recognized as material derived from carbohydrates. Pseudo-lignin is an aromatic substance. Similar to lignin, it also affects enzymatic hydrolysis efficiency by blocking the enzymatic reaction sites of cellulose and non-productive adsorption with cellulases. In order to offer theoretical guidance and technical support for the advancement of cost-effective and efficient new pretreatment technology, this review summarizes the latest advancements in research concerning the origins of pseudo-lignin, its effects on enzymatic hydrolysis, and the strategies that inhibit pseudo-lignin formation. • Different pretreatment methods that result in the formation of pseudo-lignin are reviewed. • The specific mechanism of pseudo-lignin formation is clarified. • The deposition of pseudo-lignin inhibits enzymatic hydrolysis. • Measures to hinder the formation of pseudo-lignin are discussed. [ABSTRACT FROM AUTHOR]

Corn cob is one of lignocellulosic material used for bioethanol production due to its high content of cellulose which can be converted into glucose through enzymatic hydrolysis. Unfortunately, the hydrolysis process is time consuming and the yield is relatively low. It is necessary to develop a more efficient process by applying optimum conditions. The objective of this research is to study the effect of the substrate concentration and the stirring rate on the amount of the glucose produced, to optimize these parameters and to derive a kinetic model of the enzymatic hydrolysis process studied. Pre-treated corn cobs and multiple enzymes (Cellic® C-Tec2 and Cellic® H-Tec2 from Novozymes) are used. The results show that the higher substrate concentration and the higher stirring rate lead to a higher amount of glucose. However, if the stirring rate is greater than 150 rpm, the enzymes activity decreases as they are sensitive to a mechanical stress. The optimum values of the substrate concentration and the stirring rate in case of corn cobs enzymatic hydrolysis are equal to 15 % (w/v) and 150 rpm, respectively. The kinetics of the process studied is well described by the model of Yi Zhouliang and E. Barson leading to values of Vmax and KM of 0.0043 mg/ml h and 2.856 mg/ml, correspondingly. [ABSTRACT FROM AUTHOR]

In this work, a mathematical model is proposed to predict the kinetic behaviour of the enzymatic conversion of various types of lignocellulosic biomass into fermentable sugars. Digestion of the cellulosic polymers is carried out using enzymatic hydrolysis under different conditions. Unlike other kinetic models, published previously for this process, this one considers the heterogeneous nature of the process by which a solid, in the form of small particles, is decomposed to monosaccharides by the action of a diverse set of enzymes in solution. The effect of the particle size on the hydrolysis rate has also been taken into consideration. To assess the model's goodness of fit to any general situation, the experimental data obtained in the hydrolysis of three different lignocellulosic residues have been analysed. Thus, the hydrolysis data of wheat straw, rice husks and exhausted sugar beet pellets have been compared with the theoretical values calculated by the model. The results obtained show that this model predicts the enzyme's hydrolysis of lignocellulosic substrates under different conditions very accurately and it could therefore be used efficiently in the optimization of the hydrolysis processes implemented in the bio‐refinery industry. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Highlights • Ultrasound-assisted acid hydrolysis (UAAH) of lignocellulosic biomass conversion into furfural. • Reaction time, ultrasound amplitude, and feedstock amount were evaluated using a cup horn system. • UAAH is performed at atmospheric pressure and under milder reaction conditions in contrast to conventional process. • Lignin removal is not required in the present UAAH procedure. • About 7.2% of grass (whole mass) was converted to furfural, using. • 4 mol L−1 HNO 3 , at 30 °C, 50% of amplitude and 60 min of sonication. Abstract Furanic platforms (e.g. furfural, furfuryl alcohol and hydroxymethylfurfural) can be obtained from biomass, being considered as a green alternative to petrochemical products such as fuels, and solvents. In this work, the use of ultrasound energy was investigated for the conversion of several lignocellulosic materials into furfural. The following parameters were evaluated: reaction time (30 to 120 min), ultrasound amplitude (20 to 70%) and feedstock amount (100 to 500 mg). The ultrasound-assisted acid hydrolysis (UAAH) process was applied to several lignocellulosic materials (sugar cane straw, rice husk, yerba-mate waste, grass and wood waste) aiming an investigation about the effects when working with real and complex feedstock. Better furfural yields (72.4 ± 4.3 mg g−1) were obtained from 0.1 g of grass, employing an ultrasound cup horn system operating at 20 kHz, 20 mL of 4 mol L−1 HNO 3 , at 30 °C, 50% amplitude, and 60 min of sonication. Under the same reaction conditions, the results were compared with those obtained at silent condition (mechanical stirring, 100 to 500 rpm), which demonstrate the ultrasound effects for furfural synthesis. Therefore, the proposed UAAH process can be considered as a suitable alternative for biomass conversion to furfural, because it does not need previous step of lignin removal and might be performed in a single step. [ABSTRACT FROM AUTHOR]

Abstract Working at high values of lignocellulosic Dry Matter (DM), as wheat straw, increases the reaction medium viscosity, making the mixing inefficient with the traditional agitators. Batch and fed-batch tests were conducted using different impellers: i) inclined blades, ii) marine impeller, iii) anchor, iv) paravisc and v) double helical impeller. Inclined blades appeared an inadequate device for batch and fed-batch tests. On contrary, double helical impellers and anchor gave optimal performances. An alternative to improve the reactor's rheology is the modification of the feeding strategy. A particular fed-batch strategy allowed keeping low the reaction medium viscosity by a gradual increasing of the DM content in the reactor. In this way, three main benefits were achieved: i) a very good performances in terms of glucose concentration (85 g/L), ii) a strong reduction of the energetic consumption compared to batch test and iii) the adoption of a simple mixing devise. Graphical abstract Image Highlights • Enzymatic hydrolysis from wheat straw causes bad mixing at high DM content. • Different impellers have been tested in batch and fed-batch mode. • Small impellers were inefficacy, double helical impeller had high performances. • A fed-batch strategy (FBGA) has been implemented to use small impellers. • FBGA allowed to minimize energy consumption and to increase the glucose yield. [ABSTRACT FROM AUTHOR]

The goal of this study was to sequential fermentation of hydrogen and methane from sugarcane bagasse (SCB). Steam explosion conditions for pretreating SCB were optimum at 195 °C and 1.5 min, which yielded 36.35 g/L of total sugar and 2.35 g/L of total inhibitors. Under these conditions (all in g/L): glucose, 11.33; xylose, 24.41; arabinose, 0.61; acetic acid, 2.33; and furfural, 0.02 were obtained. The resulting hydrolysate was used to produce hydrogen by anaerobic mixed cultures. A maximum hydrogen production rate of 396.50 mL H 2 /L day was achieved at an initial pH of 6 and an initial total sugar concentration of 10 g/L. The effluent from the hydrogen fermentation process was further used to produce methane. Response surface methodology with central composite design was used to obtain the suitable conditions for maximizing methane production rate (MPR). An MPR of 185.73 mL/L day was achieved at initial pH, Ni and Fe concentrations of 7.59, 3.61 mg/L and 8.44 mg/L, respectively. Total energy of 304.11 kJ/L-substrate was obtained from a sequential fermentation of hydrogen and methane. This approach will not only add value to SCB, in the form of safe and clean energy, but also provide a solution for making use of this abundant waste. [ABSTRACT FROM AUTHOR]

In the present study, we pretreated the plant Guinea grass (Panicum maximum) with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate [EMIM][OAc] to expose its cellulose fibers. For this, we first determined the composition of Guinea grass, with 6.87 ± 1.21% of ash, 14.33 ± 1.18% of lignin, 70.55 ± 1.15% of holocellulose, 29.9 ± 1.20% of cellulose, and 40.65 ± 1.20% of hemicellulose. After characterizing the material, we determined the IL pretreatment conditions that maximized the enzymatic and acid hydrolysis stages [namely: temperature = 157 °C, reaction time = 30 min, and biomass concentration (relative to total mass) = 14%]. Under these conditions, the enzymatic hydrolysis conversions of glucose and total reducing sugars were respectively 69.8 and 54.2%, determined by enzymatic and DNS methods. The acid hydrolysis was also carried out, and conversions of 57.4 and 27.2% were verified by the enzymatic and DNS methods, respectively. Finally, the hydrolysate obtained after the enzymatic hydrolysis was fermented by the yeast Saccharomyces cerevisiae, and the ethanol yield (81.9%) was determined through gas chromatography. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the capacity a cellulolytic complex produced by Rhizopus oryzae has to provide functional compounds from lignocellulosic material. Its characterization upon soybean meal (SBM) and corn husk (CH) was carried out. The effect was estimated in terms of cellulose reduction and protein and starch digestibility, besides the content of phenolic compounds (PC) and their profiles. Enzymatic hydrolysis caused 34% cellulose reduction in SBM whereas, in CH, it was 55%. In CH, the reduction promoted PC release (21%). The greatest change in the antioxidant activity after hydrolysis was found in phenolic compounds soluble in methanol (PCSM), a fact that could be attributed to concomitant reduction in ferulic acid and increase in hydroxybenzoic acid. In SBM, the activity of the cellulolytic complex caused increases in protein (74%) and starch (95%) digestibility. Therefore, available protein in SBM can be used as food supplement and thickener whereas PC derived from CH may be applied as food additive. [ABSTRACT FROM AUTHOR]

Agricultural feedstocks (brewers’ spent grain – BSG, corncob – CC, corn husk – CH, wheat straw – WS and Luffa sponge – LS) were pretreated by liquid hot water (LHW) in order to increase cellulose recovery and enzymatic saccharification. LHW-pretreatment resulted in hemicellulose solubilization, and solids enriched in cellulose. Chemical analysis showed different susceptibilities of the feedstocks to LHW-pretreatment and enzymatic hydrolysis. Pretreated feedstocks presented higher crystallinity (determined through X-ray diffraction) and thermal stability (determined through thermogravimetric analysis) than untreated feedstocks. SEM images confirmed the effect of LHW-pretreatment on structural changes. Moreover, enzymatic hydrolysis and cellulose conversion to glucose (CCG) were improved for pretreated feedstocks, with exception of LS. CCG (in relation to glucose potential on solids) followed the order: BSG > CH > WS > CC > LS. LHW-pretreatment showed to be a good technology to pretreat multi feedstocks and for improving the enzymatic hydrolysis of recalcitrant agricultural feedstocks to sugars, which can be further converted to ethanol-fuel and other value-added chemicals. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of microwave (MW) and microwave–chemical (MWC) pretreatment on barley straw and to identify the acidic, basic, or oxidative chemicals that provide the highest sugar conversion for subsequent enzymatic hydrolysis. The MW and MWC processes were applied as a pretreatment step before fermentation. MW radiation at 200 and 300 W and MW radiation plus a chemical (H2SO4or NaOH or H2O2) as catalyst were applied, and total sugar, total phenol, and Klason and acid-soluble lignin were measured. Although the MWC pretreatment produced a higher total sugar concentration than the MW pretreatment, the addition of an NaOH solution produced the best results in terms of all parameters. Fourier transform infrared analysis was also performed to observe the deterioration of molecular structures after the application of MW and MWC. [ABSTRACT FROM PUBLISHER]

Lignocellulosic materials are potential renewable substrates for fermentative H 2 production; however, most of the methods available to hydrolyze these materials produce fermentation inhibitors. This study assessed the effect of three different groups of inhibitors on fermentative H 2 production by a mixed culture: (1) acetic acid; (2) furan derivatives, such as furfural and 5-hydroxymethylfurfural (HMF); and (3) phenolic monomers, such as vanillin, syringaldehyde, and 4-hydroxybenzoic acid (HBA). Conduction of batch assays in the presence of glucose and different concentrations of inhibitors helped to assess how the inhibitors affected the kinetic parameters of the modified Gompertz model ( R m , H max , and λ ). The concentrations of inhibitors that reduced 50% of the maximum H 2 production rate (IC50) were estimated. In terms of IC50, HBA provided the largest inhibition, 0.38 g L −1 , which is a novel result in the literature. HBA was followed by HMF and furfural, 0.48 and 0.62 g L −1 , respectively. Vanillin, syringaldehyde, and acetic acid at 0.71; 1.05; and 5.14 g L −1 provided the same inhibition level, respectively. Knowledge about the degree of inhibition of these compounds shall contribute to sustainable H 2 production from lignocellulosic substrates. [ABSTRACT FROM AUTHOR]

This work proposes the biorefining of eucalyptus residues (ER), wheat straw (WS) and olive tree pruning (OP) combining hydrothermal pretreatment (autohydrolysis) with acid post-hydrolysis of the liquid fraction and enzymatic hydrolysis of the solid fraction towards maximal recovery of monosaccharides from those lignocellulose materials. Autohydrolysis of ER, WS and OP was performed under non-isothermal conditions (195–230 °C) and the non-cellulosic saccharides were recovered in the liquid fraction while cellulose and lignin remained in the solid fraction. The acid post-hydrolysis of the soluble oligosaccharides was studied by optimizing sulfuric acid concentration (1–4% w/w) and reaction time (10–60 min), employing a factorial (2 2 ) experimental design. The solids resulting from pretreatment were submitted to enzymatic hydrolysis by applying commercial cellulolytic enzymes Celluclast® 1.5 L and Novozyme® 188 (0.225 and 0.025 g/g solid, respectively). This strategy provides high total monosaccharide recovery or high glucose recovery from lignocellulosic materials, depending on the autohydrolysis conditions applied. [ABSTRACT FROM AUTHOR]

This paper is a state-of-the-art review and a consolidated source of information regarding the prebiotic potential of xylooligosaccharides (XOS) derived from lignocellulosic materials (LCM) as bioactive molecules with high-added value for human health. XOS can be obtained by hydrothermal pretreatment (or autohydrolysis), a primary technological step in biological conversion of LCM into value-added products. Purification of XOS is a complex process which aims to remove unwanted compounds and to achieve the necessary degree of polymerization. Proven benefits and positive effects on the human health are mainly in the intestinal microbiota, where food-grade XOS stimulate the growth and proliferation of probiotic bacteria. The main objective of this study was to provide an in-depth overview of the recent published investigations reported in the scientific literature on the production of XOS from xylan-containing LCM by hydrothermal pretreatment, purification of hydrothermally produced XOS and, furthermore, evaluation of the bioactive properties of purified XOS. [ABSTRACT FROM AUTHOR]

Highlights: [•] Dilute-acid pretreatment of Jatropha curcas shells for enzymatic hydrolysis was assessed. [•] Cellulose conversions above 80% were achieved in the enzymatic hydrolysis. [•] Optimal conversion was predicted for pretreatment at 136°C, 30min and 1.5% H2SO4. [•] Water extraction prior to pretreatment was found to further improve the enzymatic conversion. [ABSTRACT FROM AUTHOR]

Production of succinic acid via separate enzymatic hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) are alternatives and are environmentally friendly processes. These processes have attained considerable positions in the industry with their own share of challenges and problems. The high-value succinic acid is extensively used in chemical, food, pharmaceutical, leather and textile industries and can be efficiently produced via several methods. Previously, succinic acid production via chemical synthesis from petrochemical or refined sugar has been the focus of interest of most reviewers. However, these expensive substrates have been recently replaced by alternative sustainable raw materials such as lignocellulosic biomass, which is cheap and abundantly available. Thus, this review focuses on succinic acid production utilizing lignocellulosic material as a potential substrate for SSF and SHF. SSF is an economical single-step process which can be a substitute for SHF - a two-step process where biomass is hydrolyzed in the first step and fermented in the second step. SSF of lignocellulosic biomass under optimum temperature and pH conditions results in the controlled release of sugar and simultaneous conversion into succinic acid by specific microorganisms, reducing reaction time and costs and increasing productivity. In addition, main process parameters which influence SHF and SSF processes such as batch and fed-batch fermentation conditions using different microbial strains are discussed in detail. [ABSTRACT FROM AUTHOR]

Abstract: In this work, dilute sulphuric acid prehydrolysis of residual empty pods of Moringa oleifera fruits was investigated as pretreatment for enzymatic hydrolysis of cellulose. In experiments performed at 130–190°C for 10–30min, corresponding to a severity range between log R o =1.9 and log R o =4.2, the effect of pretreatment conditions on the recovery of polysaccharides and on the enzymatic convertibility of cellulose was evaluated. Overall cellulose recovery was above 95% in the pretreatments performed at 130 and 160°C, and between 87 and 90% in the pretreatments at 190°C, while xylan recovery in the most severe pretreatments was only 24.7–50.2%. The highest sugar concentration in the acid prehydrolysates (15.0g/L) was obtained in the pretreatment performed at 160°C and 20min. The formation of degradation products was low at mild pretreatment conditions, but it increased with the severity. Furfural concentration reached 4.04g/L at log R o =3.1 and decreased again with a further increase of the pretreatment severity. HMF, formic acid and levulinic acid were formed only in the most severe pretreatments. The pretreatment was effective for improving the enzymatic hydrolysis of cellulose, and the highest conversion (84.3%) was achieved in the material pretreated at mid severity (log R o =3.1). [Copyright &y& Elsevier]

Abstract: A Clostridium beijerinckii mutant RT66 with considerable inhibitor-tolerance obtained by continuous culture was used for butanol production from non-detoxified hemicellulosic hydrolysate of corn fiber treated with dilute sulfuric acid (SAHHC). In fed-batch fermentation, 1.8L of diluted SAHHC containing 10g/L of reducing sugar was provided during the acidogenic phase and 0.2L of concentrated SAHHC containing 300g/L of reducing sugar was provided during the solventogenic phase. The mutant produced a total amount of solvents of 12.9g/L, which consisted of 3.1g/L of acetone, 9.3g/L of butanol and 0.5g/L of ethanol. A solvent yield of 0.35g/g sugar and a productivity of 0.18g/Lh in 72h were achieved. The remarkable inhibitor-tolerance of C. beijerinckii RT66 demonstrates that this may be an excellent strain for butanol production from ligocellulosic materials. [Copyright &y& Elsevier]

In this review, the recent advancements and technical challenges associated with the production of ethanol, butanol, and isobutanol via bioconversion routes from celluloses of woody materials are reviewed. Physicochemical processes, e.g. steam explosion, seem to be the most viable process for pretreating woody materials. Although enzymatic hydrolysis is selective, it is rather a slow process. Acid hydrolysis is a relatively fast process with a high yield, but it produces inhibitory compounds of fermentation, which necessitates a detoxification process before the fermentation. Presently, the major challenges in the production of ethanol, butanol, and isobutanol via biological conversions are the rather low production yield and the sensitivity of microorganisms to the presence of inhibitors and products in fermentation media. In this study, the recent advancements in the applications of Saccharomyces cerevisiae, Clostridium acetobutylicum, and Corynebacterium glutamicum, the most promising microorganisms, for ethanol, butanol, and isobutanol production are also discussed. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29: 297-310, 2013 [ABSTRACT FROM AUTHOR]

Abstract: The increasing cost of vegetable oils is turning the use of microbial lipids into a competitive alternative for the production of biodiesel fuel. The oleaginous yeast Rhodotorula graminis is able to use a broad range of carbon sources for lipid production, and is able to resist some of the inhibitors commonly released during hydrolysis of lignocellulosic materials. Using undetoxified corn stover hydrolysate as substrate, the yeast achieved a lipid productivity and lipid content of 0.21g/L/h and 34%w/w, respectively. The corresponding results with crude glycerol as carbon source were 0.15g/L/h and 54%w/w, respectively. Therefore, R. graminis appears to be a suitable candidate for fermentation processes involving renewable resources. [Copyright &y& Elsevier]

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Abstract: In this study, we investigated the enzymatic hydrolysis of pretreated sugarcane bagasse using eight different enzymatic blends obtained from concentrated crude enzyme extracts produced by Penicillium funiculosum and Trichoderma harzianum as well as from the extracts in combination with a commercial enzymatic cocktail. The influence of different levels of biomass delignification, degree of crystallinity of lignicellulose, composition of enzymatic activities and BSA on enzymatic hydrolysis yields (HYs) was evaluated. Our X-ray diffraction studies showed that crystallinity of lignocellulose is not a key determinant of its recalcitrance toward enzymatic hydrolysis. In fact, under the experimental conditions of our study, an increase in crystallinity of lignocellulosic samples resulted in increased glucose release by enzymatic hydrolysis. Furthermore, under the same conditions, the addition of BSA had no significant effect on enzymatic hydrolysis. The most efficient enzyme blends were obtained by mixing a commercial enzymatic cocktail with P. funiculosum or T. harzianum cellulase preparations (HYs above 97%) followed by the concentrated extract of P. funiculosum alone (HY=88.5%). Increased hydrolytic efficiencies appeared to correlate with having an adequate level of both β-glucosidase and xylanase activities in the blends. [Copyright &y& Elsevier]

Abstract: Lignocellulosic materials, such as agricultural residues, are abundant renewable resources for bioconversion to sugars. The sugar cane bagasse was studied here to obtain simple sugars for the production of alcohols and other chemicals. The crystalline structure of cellulose and the lignin that physically seals the surrounding cellulose fibers makes enzymatic hydrolysis difficult by preventing the contact between the cellulose and the enzyme. Two different samples of sugar cane (bagasse pulp and skin) were used and compared with microcrystalline cellulose (Avicel). The investigated samples were pretreated with SC-CO2 explosion before hydrolysis. The experiments were conducted at 12, 14 and 16MPa at a temperature of 60°C. In this process, particles of celluloses within the size range from 0.25 to 0.42mm were placed in defined amounts inside the experimental vessel, CO2 was injected and let stand for 5 and 60min. The explosion pretreatment of cellulosic materials by SC-CO2 was performed in an apparatus of a static type with 300ml of volume. The hydrolysis reaction using cellulose enzyme was carried at 55°C for 8h. After the pretreatment, the glucose yield increased in 72% to the bagasse sample. The SC-CO2 pretreatment together with alkali increased the glucose yield in 20% as compared with alkali only. X-ray, microscopy and thermal analysis were used to investigate the effect of the pretreatment. [Copyright &y& Elsevier]

Abstract: Rice hulls (RH) and bean hulls (BH) were subjected to prehydrolysis treatments, to define the optimum conditions for producing a high percentage of hydrolyzed hemicellulose with a small or moderate degradation of the cellulosic portion. The hydrolysis experiments were performed using hydrochloric and sulfuric acids in concentrations ranging from (0.5 to 5)% (w/w) at 120°C for 90min and 10% consistency. The effects of different temperatures (80 to 120°C) and time (30 to 120min) on acid hydrolysis of lignocellulosic materials were recorded. It was found that, the optimum condition to hydrolyze the lignocellulosic materials (RH) and (BH) are 2% (w/w) of mineral acid at 120°C for 90min and 10% consistency. The cellulose crystallinity index in the different types of lignocellulosic materials with and without acid treatment, were increased from 0.32 to 0.46 in case of RH and from 0.43 to 0.61 in case of BH. Due to the lignin depolymerization during the pretreatment process, the relative absorbency of the methoxyl group and the aromatic rings bands were lowered for the pretreated than the untreated lignocellulosic materials. Also, the band at 1730cm−1 which is attributed to carbonyl groups of uronic acids was lowered due the hemicellulose hydrolysis. [Copyright &y& Elsevier]

The effectiveness of various chemicals pretreatment (NaOH, HCl, NH3, HNO3 and EDTA) on the enzymatic saccharification of solid palm oil mill effluent (POME) and oil palm fruit fibre (OPFF) was investigated. The results showed that NaOH seem to be the most suitable chemical pretreatment for enhancing sugar production and the degree of hydrolysis from saccharification of OPFF. NaOH at a concentration of 2% (w/v) appears to be optimal for alkaline pretreatment of OPFF. However, chemical pretreatment of solid POME using NaOH, NH3, HNO3, HCl and EDTA was found to be ineffective in enhancing the degree of hydrolysis and sugar production as compared to chemically untreated solid POME. Autoclaving OPFF at 121°C, 15 psi for 5 minutes improved the degree of hydrolysis up to 2.4 times. However, the degree of hydrolysis was not significantly affected for solid POME under the same conditions. [ABSTRACT FROM AUTHOR]

Macaúba husks are inedible lignocellulosic wastes obtained after extracting oil from the fruit for biodiesel production. The objective of this study was to valorize macaúba husks through subcritical water hydrolysis (SWH) pretreatment followed by anaerobic digestion (PT+AD) in comparison to a control reactor (CR). The semi-continuous parameters were: 10 g of dried husk; flow rate of 10 mL/min at 200 °C and 14 MPa and for a total reaction time of 40 min. For AD, mesophilic conditions (35 °C) were kept for both experimental trials. For the PT+AD experiment, digestion was performed for 38 days and for 39 days for the CR experiment. The chemical oxygen demand (COD) removal for the PT+AD reactor was 48% and 43% for CR, indicating the pretreatment improved digestibility of the organic feed. Similarly, the CH 4 yield per unit of COD for 590 mL CH 4 /g COD for the PT+AD experiment compared with 57 mL CH 4 /g COD for the CR experiment. The corresponding biogas yield was 161% greater than in the PT+AD experiment compared with the CR. Energy analysis revealed a corresponding benefit from SWH for production of heat and power, and several recommendations were made for decreasing the heat required by SWH to make the process self-sufficient. Macaúba cultivation has promise as an energy crop that can be grown locally in Brazil and similar tropical locations for co-production of biodiesel from the extracted oil and biogas from the husks, thereby avoiding greenhouse gas emissions by replacement of traditional fossil sources. [Display omitted] • Valorization of macaúba by-products through subcritical water hydrolysis and anaerobic digestion for biogas. • Subcritical water hydrolysis is adequate as a pretreatment for lignocellulosic. • Macaúba by-products are suitable for biogas production after pretreatment of the lignocellulosic material. • The energy assessment of macaúba husks was favorable to obtain electricity and thermal energy in a combined heat and power system. [ABSTRACT FROM AUTHOR]

• Pecan raws were processed by subcritical water hydrolysis to obtain reducing sugars. • Different process conditions (temperature; water to solid mass ratio) were evaluated. • 27.1 ± 6.9 g reducing sugars/100 g biomass were obtained at 220 °C for shells. • Efficiency in producing reducing sugars were up to 78 wt%. • The strategy proved to be a clean alternative for adding value to pecan coproducts. Pecan cultivation has increased in recent years. Consequently, the amount of lignocellulosic residuals from its production has expanded. Thus, there is a necessity to explore and add value to their coproducts. The objective of this work was to obtain reducing sugars from pecan biomasses by the optimization of the subcritical water hydrolysis technology in a semi-continuous mode and the physicochemical and morphological characterization of these materials, such as SEM, TGA and FT-IR analysis. Temperatures of 180, 220 and 260 °C, water/solids mass ratio of 15 and 30 g water/g biomass and total reaction time of 15 min were used. The highest reducing sugar yield was 27.1 g/100 g of biomass, obtained at 220 °C and R-15 for pecan shells. TGA, SEM and FT-IR analysis indicated the modifications of structures and compositions of biomasses in fresh and hydrolyzed samples. [ABSTRACT FROM AUTHOR]

• Study into intensification of delignification and enzymatic hydrolysis of sawdust. • Understanding into effect of operating parameters to maximize intensification. • Ultrasound assisted approach yields significant reduction in reaction time. • Significant increase in lignin removal and reducing sugars production. The current work investigates intensification of delignification of sawdust and subsequent enzymatic hydrolysis to produce reducing sugars with the use of ultrasound. Alkaline hydrolysis of sawdust was initially performed to remove lignin which hampers the rate of enzymatic hydrolysis. Effect of different parameters in the case of ultrasound (US) assisted and conventional processes such as alkali concentration (0.5–2.5 N), substrate loading (0.2–1.0% w/v) and temperature (40–80 °C) have been investigated. Optimized parameters obtained for US assisted process showed better trends as compared to conventional process with about 1.25 times higher yields and significant reduction in time by about 4 h. The process parameters for US assisted and conventional enzymatic hydrolysis to produce reducing sugars were also optimized by varying substrate loading (0.5–10% w/v), reaction temperature (30–70 °C) along with variation in US power (10–80 W) and US duty cycle (30–90%). US assisted enzymatic hydrolysis performed at 4% w/v substrate loading along with 50 W US power and 50% duty cycle at 50 °C resulted in 7.46 mg/mL of reducing sugars yield within 1 h while conventional stirring with 6% w/v substrate loading and 50 °C resulted in approximately same yield of reducing sugars within 3 h. The requirement of lower time for similar yields or in other words higher yield in same time clearly highlights the process intensification benefits due to the use of ultrasound. Overall it can be concluded from the study that US assisted processes resulted in efficient delignification along with higher yield of reducing sugars in lower treatment time as compared to conventional process. [ABSTRACT FROM AUTHOR]