Production of xylose,furfural, fermentable sugars and ethanol from agricultural residues

With the developing shortage of petroleum, reliance on biomass as a source of chemicals and fuels will increase. In the present work, bagasse and rice husk were subjected to dilute acid (H₂SO₄) hydrolysis using pressurised water to obtain furfural and fermentable sugars. Various process conditions such as particle size, solid-liquid ratio, acid concentration, reaction time and temperature have been studied to optimise yields of furfural, xylose and other fermentable sugars. The use of particle sizes smaller than 495 μm did not further increase the yield of reducing sugars. A solid-liquid ratio of 1:15 was found to be the most suitable for production of reducing sugars. Hydrolysis using 0.4% H₂SO₄ at 453 K resulted in selective yields (g per 100 g of dried agricultural residues) of xylose from bagasse (22.5%) and rice husk (21.5%). A maximum yield of furfural was obtained using 0.4% H₂SO₄ at 473 K from bagasse (11.5%) and rice husk (10.9%). It was also found that hydrolysis using 1% H₂SO₄ at 493 K resulted in maximum yields of total reducing sugar from bagasse (53.5%) and rice husk (50%). The reducing sugars obtained were fermented to ethanol after removal of furfural. The effect of furfural on the fermentation of sugars to ethanol was also studied. Based on these studies, an integrated two-step process for the production of furfural and fermentable sugars could be envisaged. In the first step, using 0.4% H₂SO₄ at 473 K, furfural could be obtained, while in the second step, the use of 1% H₂SO₄ at 493 K should result in the production of fermentable sugars.     

Hydrolysis of sugarcane bagasse in subcritical water

In this work, a subcritical water process was used for the hydrolysis of sugarcane bagasse with the aim of producing fermentable sugars. Hydrolysis kinetics was determined using a semi-batch unit equipped with a 50 mL reactor. Different sample loads (2 and 11 g), flow-rates (11, 22, 33, 44 and 55 mL/min) and temperatures (213, 251 and 290 °C) were evaluated, while maintaining constant pressure (20 MPa). The liquefaction degree of the sugarcane bagasse was not affected by water flow rate and increased with temperature; the maximum liquefaction degree was 95% for hydrolysis at 251 °C and 33 mL/min. The total reducing sugars recovered increased with flow rate up to 23%. The hydrolysis process was completed faster at higher temperatures, requiring 16 min. Maximum monosaccharides + cellobiose + cellotriose yield was 5.6% at 213 °C and 33 mL/min. Approximately 60% of the sugars recovered were in the oligomeric form.     

Extracellular endo-mannanase from Bacillus sp. CFR1601: Economical production using response surface methodology and downstream processing using aqueous two phase system

Bacillus sp. CFR1601, isolated from decaying plant litter, produced an extra-cellular endo-mannanase (198.0 IU/g) under solid state fermentation (SSF) using defatted coconut residue as the prime solid substrate. In order to enhance endo-mannanase production, three component, five level central composite design (CCD) of response surface methodology (RSM) was used. Based on contour plots and variance analysis, optimum conditions for endo-mannanase production from Bacillus sp. CFR1601 were attained when defatted coconut residue was supplemented with sesame oil meal (10.0, w/w), Tween-80 (0.2%, v/v) and inoculated with bacterial cells from log phase (12 h old; OD_600 nm ≈ 3.6). The empirical model developed through RSM brought about 4.04–4.39-fold (800.0–870.0 IU/g) improvement in endo-mannanase yield as compared to un-optimized growth conditions. Downstream processing of endo-mannanase from SSF media was carried out for the first time using polyethylene glycol (PEG)/salt aqueous two phase system (ATPS). ATPS system consisting of a combination of PEG 3350 12.0% (w/w), Na₂SO₄ 12.0% (w/w), protein load 10.0% (w/w) and pH 5.0 resulted in one-sided partitioning of endo-mannanase towards bottom phase with 3.8-fold purification and 95.4% recovery. Second stage ATPS with fresh top phase further improved purification of endo-mannanase to 12.32-fold. Our overall results suggest a cost-effective and integrated process for production and downstream processing of endo-mannanase.     

Monolithic acidic catalysts for the dehydration of xylose into furfural

We report the application of hierarchically porous zirconium phosphate monoliths with high surface area as acidic heterogeneous catalysts for the dehydration of xylose into furfural. Analyses by NH₃-temperature programmed desorption and ³¹P solid state NMR reveal the presence of both Lewis and Brønsted acid sites in the as-synthesized zirconium phosphate monolith and that calcined at 600 °C. High accessibility and availability of the acidic sites and easy separation of the monolith from the liquid medium result in good catalytic activity (initial reaction rate for furfural production as 8.7 mmol g_cat^− 1 h^− 1) with easy handling of the catalyst.     

Potential use of different agroindustrial by-products as supports for fungal ellagitannase production under solid-state fermentation

Ellagitannase is a novel enzyme responsible for biodegradation of ellagitannins and ellagic acid production. Ellagic acid is a bioactive compound with great potential in food, pharmaceutical and cosmetic industries. This work describes the ellagitannase enzyme production from partial purified ellagitannins as inducers by Aspergillus niger GH1 grown on solid-state fermentation. Solid-state fermentation was carried out on four different lignocellulosic materials (sugarcane bagasse, corn cobs, coconut husks and candelilla stalks) as matrix support and production of ellagitannase enzyme was evaluated. All lignocellulosic materials were characterized in terms of water absorption index and critical humidity point. The best lignocellulosic materials for ellagitannase production were sugarcane bagasse and corn cobs (1400 U L⁻¹ and 1200 U L⁻¹, respectively). The lowest values were obtained with candelilla stalks (500 UL-1). The highest specific productivity was obtained with corn cobs (2.5 U mg⁻¹ h⁻¹) which enable increase ellagitannase productivity up to 140 times. Corn cobs have great potential as support matrix for production of fungal ellagitannase in SSF.     

An approach to optimization of enzymatic hydrolysis from sugarcane bagasse based on organosolv pretreatment

BACKGROUND: The organosolv pretreatment followed by enzymatic hydrolysis of the pretreated material and subsequent fermentation of the hydrolysate produced, was the strategy used for ethanol production from sugarcane bagasse. The effect of different operational variables affecting the pretreatment (the catalyst type and its concentration, and the pretreatment time) and enzymatic hydrolysis stage (substrate concentration, cellulase loading, addition of xylanase and Tween 20, and the cellulase/β‐glucosidase ratio), were investigated. RESULTS: The best values of glucose concentration (28.8 g L^?1) and yield (25.1 g per 100 g dry matter) were obtained when the material was pretreated with 1.25% (w/w) H₂SO₄ for 60 min, and subsequently hydrolyzed using 10% (w/v) substrate concentration in a reaction medium supplemented with xylanase (300 UI g^?1) and Tween 20 (2.5% w/w). Fermentation of the broth obtained under these optimum conditions by Saccharomyces cerevisiae resulted in an ethanol yield of 92.8% based on the theoretical yield, after 24 h. CONCLUSION: Organosolv pretreatment of sugarcane bagasse under soft conditions, and subsequent enzymatic hydrolysis of the pretreated material with a cellulolytic system supplemented with xylanase and Tween 20, is a suitable procedure to obtain a glucose rich hydrolysate efficiently fermentable to ethanol by Sacharomyces cerevisiae yeasts. Copyright © 2010 Society of Chemical Industry     

Integrated supercritical fluid extraction and subcritical water hydrolysis for the recovery of bioactive compounds from pressed palm fiber

Pressed palm fiber (PPF), a residue obtained from palm oil industry, is a source of bioactive compounds, such as carotenoids, which are used as food additives. It also has cellulose and hemicellulose that can be used to yield fermentable sugars for the production of second generation ethanol. Supercritical fluid extraction (SFE) of pressed palm fiber provides an oil rich in carotenoids while subcritical water hydrolysis (SubWH) produces hydrolysates with high amounts of fermentable sugars. In this work, the effects of pressure (15–30 MPa) and temperature (318 and 328 K) on SFE of carotenoids were investigated. The SFE extract with highest carotenoid content was obtained at 318 K and 15 MPa (2.3% d.b., 0.81 mg β-carotene/g extract). After the extraction, the influence of process temperature (423–633 K), pressure (15 and 25 MPa), solvent:feed ratio (120 and 240), and residence time (1.25–5 min) on SubWH of the extraction residue was studied. At the temperature of 523 K, the highest total reducing sugar yield (11–23 g glucose/100 g carbohydrate) and the highest biomass conversion (40–97%) were obtained for any pressure and solvent:feed ratio. The highest selectivity for saccharide formation was found at 423 K (20–59 mol glucose/mol furfural equivalent). Optimal conditions for high saccharide formation and low sugar degradation product in subcritical hydrolysis were obtained at 523 K, 15 MPa, solvent:feed ratio of 120, residence time of 2.5 min with a total reducing sugar yield of 22.9 g glucose/100 g carbohydrate and a conversion of 84.9%.     

Kinetic studies of hemicellulose hydrolysis of corn stover at atmospheric pressure

The object of this work was to study the xylose production by hydrolysis of corn stover with diluted sulfuric acid at 100 °C. Several concentrations of H₂SO₄ (2%, 4% and 6% w/w) and reaction time (0–300 min) were evaluated. Kinetic parameters of mathematical models for predicting the concentrations of xylose, glucose and furfural in the hydrolysates were found. Optimal conditions for hydrolysis were 5.5% H₂SO₄ at 100 °C for 60 min; under these conditions, 86.7% of xylose yield and 2.82 g/g selectivity were attained, leading to liquors containing up to 18.73 g/l xylose, 6.64 g/l glucose and 0.63 g/l furfural. The models could be successfully used to predict the concentrations of xylose, glucose and furfural within 0–300 min under experimental acid concentrations. Furthermore, the hydrolysis process of corn stover using dilute acid could be conceived as the first stage of an integrated strategy for corn stover utilization.     

Biodiesel production from waste tallow

In the present investigation an attempt has been made to use waste tallow as low cost sustainable potential feed stock for biodiesel production. Effect of various process parameters such as amount of catalyst, temperature and time on biodiesel production was investigated. The optimal conditions for processing 5 g of tallow were: temperature, 50 and 60 °C; oil/methanol molar ratio 1:30 and 1:30, amount of H₂SO_4, 1.25 and 2.5 g for chicken and mutton tallow, respectively. Under optimal conditions, chicken and mutton fat methyl esters formation of 99.01 ± 0.71% and 93.21 ± 5.07%, was obtained after 24 h in the presence of acid. The evaluation of transesterification process was followed by gas chromatographic analysis of tallow fatty acid esters. A total of 98.29% and 97.25% fatty acids were identified in chicken and mutton fats, respectively. Both fats were found highly suitable to produce biodiesel with recommended fuel properties.     

Production of polyphenol extracts from grape bagasse using supercritical fluids: Yield,extract composition and economic evaluation

The objective of this work was to determine the economic feasibility of large-scale operations of supercritical fluid extraction (SFE) for the recovery of phenolics using grape bagasse from Pisco residues. Experimental data were used to estimate the extraction kinetic parameters, as well as the cost of manufacturing the extracts. Experimental data were obtained using supercritical CO₂ containing 10% ethanol (w/w) at 313 K and 20–35 MPa. The supercritical CO₂/ethanol extraction process produced extracts with higher concentrations of phenolics than extracts produced using conventional techniques. The compounds identified in the extracts were syringic, vanillic, gallic, p-hydroxybenzoic, protocatechuic and p-coumaric acids, as well as quercetin. An evaluation of the economics of the process indicated the feasibility of an industrial SFE plant with a capacity of 0.5 m³ for producing an extract with an expected phenolics concentration of approximately 23 g/kg of extract at an estimated cost of manufacturing of US$ 133.16/kg.     

Biodiesel production from waste cooking oil in a microtube reactor

Waste cooking oil (WCO) was used to produce biodiesel in a microtube reactor. First, the acid value of the WCO was reduced from 3.96 mg KOH/g to less than 1 mg KOH/g via acid catalyzed esterification. The effects of the methanol-to-WCO molar ratio (4.5:1–18:1), the H₂SO₄ concentration (0.5–2 wt.%), reaction temperature (55–70 °C), and reaction time (5–20 s) were studied. The optimal conditions were 9:1 methanol-to-WCO molar ratio, 1 wt.% H₂SO₄, 65 °C and 5 s of reaction time. Triglycerides in the product from the first step were transesterified with methanol and alkaline catalyst. Methyl ester content of the biodiesel was 91.76%.     

Carbocatalytic dehydration of xylose to furfural in water

Graphene, graphene oxide, sulfonated graphene, and sulfonated graphene oxide (SGO) have been prepared, characterized and tested for the dehydration of xylose to furfural in water. In particular, SGO was proven to be a rapid and water-tolerant solid acid catalyst even at very low catalyst loadings down to 0.5 wt.% vs xylose, maintaining its initial activity after 12 tested repetitions at 200 °C, with an average yield of 61% in comparison to 44% for the uncatalyzed system. Raman spectroscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, ¹³C solid state nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy and surface area analysis suggested that the aryl sulfonic acid groups were the key active sites for high temperature production of furfural in water. They were more thermally stable under the reaction conditions and acidic than other functional groups attached to the graphene surface.     

Was pretreatment beneficial for more biogas in any process? Chemical pretreatment effect on hydrogen–methane co-production in a two-stage process

The study focused on the mesophilic anaerobic hydrogen production from PPS (pulp and paper sludge) and FW (food waste) pretreated by NaOH or H₂SO₄, and the subsequent thermophilic anaerobic methane production with the effluent in a two-stage process. The maximum hydrogen yield (78.35 mL g^?1 VS_fed) which was 50.21% higher than that of CK, was achieved when 10 g NaOH/100 g TS_substrate was used. However, the maximum methane yield (383.8 mL g^?1 VS_fed) was obtained in CK as well as 64% SCOD removal efficiency was achieved. In short, NaOH/H₂SO₄ pretreatment was suitable to enhance the hydrogen production.     

Wet oxidation pretreatment of lignocellulosic residues of sugarcane,rice, cassava and peanuts for ethanol production

Wet oxidation (WO) pretreatment of sugarcane bagasse, rice hulls, cassava stalks and peanut shells was investigated. WO was performed at 195 °C for 10 min, with 2 g kg^?1 of Na₂CO₃ and under either 3 or 12 bar of oxygen. Oxygen pressure and the type of raw material used had a major effect on the fractionation of the materials, formation of sugars and by‐products, and cellulose enzymatic convertibility. Cellulose content in the solid fraction increased after pretreatment of all materials, except rice hulls. The greatest increase, from 361 g kg^?1 to almost 600 g kg^?1, occurred for bagasse. The solubilisation of individual components was different for each material. Bagasse xylan was solubilised to a large extent, and 45.2% of it was recovered as xylose and xylo‐oligosaccharides in the liquid fraction. In the prehydrolysates of rice hulls around 40% of the original glucan was recovered as gluco‐oligosaccharides, due to hydrolysis of starch contained in grain remains. The formation of by‐products was modest for all the materials, but increased with increasing oxygen pressure. The highest yield of acetic acid (34–36 g kg^?1 of raw material) and furfural (0.7–1.8 g kg^?1) occurred for bagasse. The pretreatment enhanced the enzymatic convertibility of cellulose giving the best result (670.2 g kg^?1) for bagasse pretreated at the highest oxygen pressure. However, for the other materials the pretreatment conditions were not effective in achieving cellulose conversions above 450 g kg^?1. Some enzymatic conversion of xylan was observed. Copyright © 2007 Society of Chemical Industry     

The production of hypocrellin colorants by submerged cultivation of the medicinal fungus Shiraia bambusicola

Hypocrellin production using submerged cultivation of the medicinal fungus Shiraia bambusicola revealed that both glucose and (NH₄)₂SO₄ were optimal carbon and nitrogen sources. Hypocrellin production increased with increasing initial glucose concentration within the range of 10–50 g l^?1 and (NH₄)₂SO₄ concentration in the range of 1–2 g l^?1. The effects of carbon and nitrogen concentration were optimized using central composite experimental design and response surface analysis; maximum hypocrellin production (196.94 ± 6.93 mg l^?1) was achieved using 45.7 g l^?1 glucose and 1.93 g l^?1 (NH₄)₂SO₄.     

Preparation of solid acid catalyst packing AAO/SBA-15-SO3H and application for dehydration of xylose to furfural

The solid acid catalyst packing AAO/SBA-15-SO₃H was prepared by the co-condensation and grafting method with porous anodic aluminum oxide (AAO) as support. FT-IR, SEM and TEM were applied to characterize the prepared samples. Results showed that catalysts prepared by two methods both contained active centers, and SBA-15 nanorod arrays grow inside a porous alumina membrane AAO and are perpendicular to the substrate. Their catalytic performances were tested for dehydration of xylose to furfural. The conversion of xylose and selectivity of furfural were 90% and 74% on the AAO/SBA-15-SO₃H(C) catalyst prepared by the co-condensation method, respectively. The deactivation and regeneration of the AAO/SBA-15-SO₃H(C) catalyst for the dehydration of xylose were also investigated, the activity of catalyst treated by 30 wt.% H₂O₂ almost was recovered.     

Preparation and hierarchical porous structure of biomorphic woodceramics from sugarcane bagasse

Biomorphic woodceramics with controllable pore structure were prepared from sugarcane bagasse impregnated with epoxy resin followed by sintering at different temperatures. The phase composition, chemical composition, morphology and pore texture of the products were characterized by XRD, FTIR, SEM, mercury porosimetry and N₂ adsorption. The biomorphic woodceramics are typical non-graphitizable carbon and display a hierarchical porous structure from micrometer (0.6–21 μm) to nanometer scale (3.1–9.3 nm). The woodceramics retain the tubular structures of sugarcane bagasse before calcination at 1100 °C. Furthermore, an increase in the sintering temperature results in the decrease of BET surface area, average pore diameter and pore volume in the mesopore scale. This work provides a simple, economical, and environmentally friendly method for the production of hierarchical porous woodceramics. The final products have their potential applications as adsorbents, catalyst supports and filters.     

Investigating the effect of porosity level and pore former type on the mechanical and corrosion resistance properties of agro-waste shaped porous alumina ceramics

The strength integrity and chemical stability of porous alumina ceramics operating under extreme service conditions are of major importance in understanding their service behavior if they are to stand the test of time. In the present study, the effect of porosity and different pore former type on the mechanical strength and corrosion resistance properties of porous alumina ceramics have been studied. Given the potential of agricultural wastes as pore-forming agents (PFAs), a series of porous alumina ceramics (Al₂O₃-xPFA; x=5, 10, 15 and 20 wt%) were successfully prepared from rice husk (RH) and sugarcane bagasse (SCB) through the powder metallurgy technique. Experimental results showed that the porosity (44–67%) and the pore size (70–178 µm) of porous alumina samples maintained a linear relationship with the PFA loading. Comprehensive mechanical strength characterization of the porous alumina samples was conducted not just as a function of porosity but also as a function of the different PFA type used. Overall, the mechanical properties showed an inverse relationship with the porosity as the developed porous alumina samples exhibited tensile and compressive strengths of 20.4–1.5 MPa and 179.5–10.9 MPa respectively. Moreover, higher strengths were observed in the SCB shaped samples up to the 15 wt% PFA mark, while beyond this point, the silica peak observed in the XRD pattern of the RH shaped samples favored their relatively high strength. The corrosion resistance characterization of the porous alumina samples in hot 10 wt% NaOH and 20 wt% H₂SO₄ solutions was also investigated by considering sample formulations with 5–15 wt% PFA addition. With increasing porosity, the mass loss range in RH and SCB shaped samples after corrosion in NaOH solution for 8 h were 1.25–3.6% and 0.44–2.9% respectively; on the other hand, after corrosion in H₂SO₄ solution for 8 h, the mass loss range in RH and SCB shaped samples were 0.62–1.5% and 0.68–3.3% respectively.     

A model system for cocomposting hydrocarbon contaminated soil by using water activity and porosity as response variables

Cocomposting of soil is the process of simultaneously stabilising organic materials and degrading toxic compounds foreign to the environment. The fraction of components in cocomposting modifies water activity (a_w), it is therefore important to define the composition of the bulk medium. Water activity and the porosity of the bulk medium were response variables applied to a system for the biodegradation of hydrocarbons in the soil. This work proposes a definition of a model system for cocomposting using hydrocarbon contaminated soil, sugarcane bagasse pith and water. The experimental mixtures were determined according to a simplex centroid design. The results were adjusted to a Scheffé multiple regression model and response surfaces were generated. In order to follow the biodegradation of hydrocarbons and a_w, an appropriate mixture (weight basis) was established at 25% sugarcane bagasse pith, 15% contaminated soil, and 60% water. This mixture was then tested in packed bed bioreactors of both 50 and 864 g, resulting in 40% biodegradation of total hydrocarbons after 150 h of composting.     

SO42−–Mn–Co–Ce supported on TiO2/SiO2 with high sulfur durability for low-temperature SCR of NO with NH3

The catalysts SO₄^2 − Mn–Co–Ce/TiO₂/SiO₂ were investigated for the low-temperature SCR of NO with NH₃ in the presence of SO₂. An excellent SO₂ durability at low temperature was obtained with the catalyst used TiO₂/SiO₂ as support and modified with SO₄^2 −. The catalyst sulfated with 0.1 mol/L H₂SO₄ solution and then calcined at 300 °C exhibited the best NO_x conversion efficiency of 99.5% at 250 °C in the presence of 50 ppm SO₂. The conversion efficiency did not decrease after repeatedly used for 8 times.