Fractional and physico-chemical characterization of hemicelluloses from ultrasonic irradiated sugarcane bagasse

The present study was undertaken to investigate the extractability of the hemicelluloses from bagasse obtained by ultrasound-assisted extraction methods. The results showed that the ultrasonic treatment and sequential extractions with alkali and alkaline peroxide under the conditions given led to a release of over 90% of the original hemicelluloses and lignin. This fact as well as the sugar composition and structural features of the isolated seven hemicellulosic fractions indicated that ultrasonication attacked the integrity of cell walls, cleaved the ether linkages between lignin and hemicelluloses, and increased accessibility and extractability of the hemicelluloses. Increasing alkali concentration from 0.5 to 2M and alkaline peroxide percentage from 0.5% to 3.0% resulted in degradation of hemicellulosic backbone as shown by a decrease in their molecular weights from 43,580 to 14,470 and 30,180 to 18,130gmol(-1), respectively. However, there were no significant differences in the structural features of the seven sequential alkali- or alkaline peroxide-soluble hemicellulosic fractions, which are composed mainly of L-arabino-(4-O-methyl-D-glucurono)-D-xylans. Ferulic and p-coumaric acids were found to be chemically linked with hemicelluloses.     

Preparation of sugarcane bagasse hemicellulosic succinates using NBS as a catalyst

The chemical modification of native sugarcane bagasse hemicelluloses with succinic anhydride using N-bromosuccinimide as a catalyst and N,N-dimethylacetamide/lithium chloride system as solvent was studied. The parameters optimised included succinic anhydride concentration by the molar ratio of succinic anhydride/anhydroxylose units in native hemicelluloses from 1:1 to 9:1, reaction time 0.5–6 h, NBS concentration 0.5–3.0%, and reaction temperature 25–85 °C required in the process. Results were also compared with other catalysts such as pyridine, DMAP, H₂SO₄, and other two tertiary amine catalysts, N-methyl pyrrolidine, and N-methyl pyrrolidinone. The degree of substitution of succinylated hemicelluloses ranged between 0.19 and 1.39, depending on the experimental conditions. FT-IR and ¹H and ¹³C NMR spectroscopic characterization of the esterified polymers indicated a monoester substitution. The thermal stability of the succinylated hemicelluloses decreased upon chemical modification.     

Production of bioethanol, methane and heat from sugarcane bagasse in a biorefinery concept

The potential of biogas production from the residues of second generation bioethanol production was investigated taking into consideration two types of pretreatment: lime or alkaline hydrogen peroxide. Bagasse was pretreated, enzymatically hydrolyzed and the wastes from pretreatment and hydrolysis were used to produce biogas. Results have shown that if pretreatment is carried out at a bagasse concentration of 4% DM, the highest global methane production is obtained with the peroxide pretreatment: 72.1 L methane/kg bagasse. The recovery of lignin from the peroxide pretreatment liquor was also the highest, 112.7 ± 0.01 g/kg of bagasse. Evaluation of four different biofuel production scenarios has shown that 63-65% of the energy that would be produced by bagasse incineration can be recovered by combining ethanol production with the combustion of lignin and hydrolysis residues, along with the anaerobic digestion of pretreatment liquors, while only 32-33% of the energy is recovered by bioethanol production alone.     

Comparative study of alkali- and acidic organic solvent-soluble hemicellulosic polysaccharides from sugarcane bagasse

Two-stage treatments of sugarcane bagasse with mild alkali and acidic 1,4-dioxane were performed. Pretreatment with 1M NaOH aqueous solution at 20, 25, 30, 35, and 40 degrees C for 18 h released 55.5%, 57.3%, 59.1%, 60.9%, and 62.1% of the original hemicelluloses, respectively. Post-treatment of the corresponding alkali-treated residue with 1,4-dioxane-2M HCl (9:1, v/v) at 87 degrees C for 2h, respectively, degraded 11.6%, 11.9%, 11.4%, 10.9%, and 10.6% of hemicelluloses (% dry starting material). It was found that the five alkali-soluble hemicellulosic preparations contained a much higher amounts of xylose (78.0-82.2%) and slightly higher uronic acids (4.8-5.8%), mainly 4-O-methyl-alpha-d-glucopyranosyluronic acid, but were lower in arabinose (9.3-11.7%) and glucose (2.2-4.1%) than those of the corresponding five acidic dioxane-degraded hemicellulosic fractions in which xylose (44.9-46.8%), arabinose (35.9-38.1%), and glucose (13.0-13.7%) were the major sugar constituents. The studies revealed that the five alkali-soluble hemicellulosic preparations were more linear and acidic, and had a large molecular weight (35,200-37,430 g mol(-1)) than those of the hemicellulosic fractions (12,080-13,320 g mol(-1)) degraded during the acidic dioxane post-treatment. This demonstrated that the post-treatment with acidic dioxane under the condition used resulted in substantial degradation of the hemicellulosic polymers. The 10 hemicellulosic samples were further characterized by FT-IR and 1H and 13C NMR spectroscopy, GPC and thermal analysis, and the results are reported.     

Acid hydrolysis of sugarcane bagasse for lactic acid production

In order to use sugarcane bagasse as a substrate for lactic acid production, optimum conditions for acid hydrolysis of the bagasse were investigated. After lignin extraction, the conditions were varied in terms of hydrochloric (HCl) or sulfuric (H₂SO₄) concentration (0.5–5%, v/v), reaction time (1–5 h) and incubation temperature (90–120 °C). The maximum catalytic efficiency (E) was 10.85 under the conditions of 0.5% of HCl at 100 °C for 5 h, which the main components (in g l⁻¹) in the hydrolysate were glucose, 1.50; xylose, 22.59; arabinose, 1.29; acetic acid, 0.15 and furfural, 1.19. To increase yield of lactic acid production from the hydrolysate by Lactococcus lactis IO-1, the hydrolysate was detoxified through amberlite and supplemented with 7 g l⁻¹ of xylose and 7 g l⁻¹ of yeast extract. The main products (in g l⁻¹) of the fermentation were lactic acid, 10.85; acetic acid, 7.87; formic acid, 6.04 and ethanol, 5.24.     

The effect of biomass moisture content on bioethanol yields from steam pretreated switchgrass and sugarcane bagasse

This study aimed to determine the effect of moisture content of three different feedstocks on overall ethanol yield. Switchgrass and sugarcane bagasse from two sources were either soaked in water (∼80% moisture) or left dry (∼12% moisture), and half each of these were impregnated with 3% w/w SO₂ and all were steam pretreated. The twelve resulting substrates were compared based on overall sugar recovery after pretreatment, cellulose conversion following enzymatic hydrolysis, and ethanol yield following simultaneous saccharification and fermentation. The overall ethanol yield after simultaneous saccharification and fermentation of hexoses was 18-28% higher in samples that were soaked prior to SO₂ addition than in SO₂-catalyzed samples that were not soaked. In samples that were uncatalyzed, soaking made little difference, indicating that the positive effect of increased moisture content may be related to increased permeability of the biomass to SO₂.     

Optimization of sugarcane bagasse conversion by hydrothermal treatment for the recovery of xylose

This work aims at the valorization of sugarcane bagasse by extracting xylose which is destined to the production of xylitol after purification and hydrogenation. Our approach consists in applying the principle of biorefinery to sugarcane bagasse because of its hemicellulose composition (particularly rich in xylan: (92%)). Optimizing of the thermal treatment was investigated. A treatment at 170 °C for 2 h was found optimal, with higher solubilzation of hemicellulose than that at 150 °C and lower degradation of sugar monomers than 190 °C. Recovery of xylose was high and the purity of xylose solution (78%) allows expecting an easy purification and separation of xylose before hydrogenation. Analysis of thermal hydrolyzates shows the presence of xylan oligomers and polymers with large distribution of DPs. This fraction should be submitted to enzymatic treatment to recover more xylose monomer.     

Delignification of sugarcane bagasse using glycerol-water mixtures to produce pulps for saccharification

This paper describes the organosolv delignification of depithed bagasse using glycerol–water mixtures without a catalyst. The experiments were performed using two separate experimental designs. In the first experiment, two temperatures (150 and 190 °C), two time periods (60 and 240 min) and two glycerol contents (20% and 80%, v/v) were used. In the second experiment, which was a central composite design, the glycerol content was maintained at 80%, and a range of temperatures (141.7–198.3 °C) and time (23–277 min) was used. The best result, obtained with a glycerol content of 80%, a reaction time of 150 min and a temperature of 198.3 °C, produced pulps with 54.4% pulp yield, 7.75% residual lignin, 81.4% delignification and 13.7% polyose content. The results showed that high contents of glycerol tend to produce pulps with higher delignification and higher polyoses content in relation to the pulps obtained from low glycerol content reactions. In addition, the proposed method shows potential as a pretreatment for cellulose saccharification.     

Enzymatic hydrolysis of sugarcane bagasse and straw mixtures pretreated with diluted acid

Abstract

In Brazil, sugarcane biomass is generated in large amounts. Sugarcane bagasse and straw are considered as an important feedstock for renewable energy and biorefinery. This paper aims to study the generation of monosaccharides (C5 and C6) from sugarcane biomass via processing bagasse or straw and mixtures of both materials (bagasse:straw 3:1, 1:1 and 1:3). Samples were pretreated with sulfuric acid which resulted in approximately 90% of hemicellulose solubilization, corresponding to around 58 g L^{? 1} of xylose. Pretreated straw showed greater susceptibility to enzymatic hydrolysis in comparison to bagasse, as shown by glucose yields of 76% and 65%, respectively, whereas the mixtures showed intermediate yields. Thus, one strategy to balance sugarcane biomass availability and possibly increasing 2G ethanol production would be to use bagasse–straw mixtures in appropriate ratios according to market fluctuations. Untreated and pretreated samples were analyzed using X-ray diffraction, but there was no relationship to enzymatic hydrolysis.     

Homogeneous modification of sugarcane bagasse cellulose with succinic anhydride using a ionic liquid as reaction medium

The homogeneous chemical modification of sugarcane bagasse cellulose with succinic anhydride using 1-allyl-3-methylimidazolium chloride (AmimCl) ionic liquid as a reaction medium was studied. Parameters investigated included the molar ratio of succinic anhydride/anhydroglucose units in cellulose in a range from 2:1 to 14:1, reaction time (from 30 to 160min), and reaction temperature (between 60 and 110 degrees C). The succinylated cellulosic derivatives were prepared with a low degree of substitution (DS) ranging from 0.071 to 0.22. The results showed that the increase of reaction temperature, molar ratio of SA/AGU in cellulose, and reaction time led to an increase in DS of cellulose samples. The products were characterized by FT-IR and solid-state CP/MAS (13)C NMR spectroscopy, and thermal analysis. It was found that the crystallinity of the cellulose was completely disrupted in the ionic liquid system under the conditions given. The data also demonstrated that homogeneous modification of cellulose with succinic anhydride in AmimCl resulted in the production of cellulosic monoester. The thermal stability of the succinylated cellulose decreased upon chemical modification.     

Utilization of sugarcane bagasse for bioethanol production: sono-assisted acid hydrolysis approach

In this study, the production of sugar monomers from sugarcane bagasse (SCB) by sono-assisted acid hydrolysis was performed. The SCB was subjected to sono-assisted alkaline pretreatment. The cellulose and hemicellulose recovery observed in the solid content was 99% and 78.95%, respectively and lignin removal observed during the pretreatment was about 75.44%. The solid content obtained was subjected to sono-assisted acid hydrolysis. Under optimized conditions, the maximum hexose and pentose yield observed was 69.06% and 81.35% of theoretical yield, respectively. The hydrolysate obtained was found to contain very less inhibitors, which improved the bioethanol production and the ethanol yield observed was 0.17 g/g of pretreated SCB.     

Production, characterization and evaluation of methylcellulose from sugarcane bagasse for applications as viscosity enhancing admixture for cement based material

In previous works, methylcellulose (MC) was prepared from sugarcane bagasse cellulose in heterogeneous medium using dimethyl sulfate (DMS) as etherification agent. MC was produced in a range of degrees of substitution (DS) from 0.70 to 1.40 and the materials showed low water solubility. In this work methylcellulose was prepared with 5 h (MC5h) of reaction with reagent substitution at each hour. MC5h showed a DS of 1.89 ± 0.04. An aqueous viscous suspension was produced with MC5h for application as viscosity enhancing admixture of cimentitious adhesive mortars. It was observed a 40.37% increase on the consistency index (CI) and a 27.70% increase on the Potential Tensile Adhesion Strength. Such characteristics show the potential of this material for the utilization in situations that require good workability, improve viscosity and adhesive properties such as for tile setting in civil engineering.     

A study on xylitol production from sugarcane bagasse hemicellulosic hydrolysate by Ca-alginate entrapped cells in a stirred tank reactor

Candida guilliermondii FTI 20037 cells were entrapped in Ca-alginate beads and used for xylitol production from sugarcane bagasse hemicellulosic hydrolysate in a stirred tank reactor (STR). Screening design and response surface methodologies were used to determine adequate cultivation conditions for this fermentation system. Quadratic models were fitted to the experimental data by regression analysis, considering the yield (Y_P/S) and the productivity (Q_P) of the xylose-to-xylitol bioconversion as dependent variables. Using a five-fold concentrated hydrolysate, air flowrate of 1.30 l/min, agitation speed of 300 rpm, initial cell concentration of 1.4 g/l and value 6.0 for the initial pH of the fermentation medium resulted in a xylitol production of 47.5 g/l after 120 h of fermentation, corresponding to a Y_P/S of 0.81 g/g and to a Q_P of 0.40 g/l h.     

Pure enzyme cocktails tailored for the saccharification of sugarcane bagasse pretreated by using different methods

The compositions and physical properties of pretreated lignocellulose vary depending on pretreatment methods; therefore, enzyme cocktails specific to pretreatments are desired for efficient saccharification of lignocellulose. Here, enzyme cocktails consisting of three pure lignocellulolytic enzymes endoglucanase (EG), cellobiohydrolase (CBH) and endoxylanase (XN) with a fixed amount of β-glucosidase were tailored for acid- and alkali-pretreated sugarcane bagasse (ACID and ALKALI, respectively). Based on a mixture design, the optimal mass ratios of EG, CBH, and XN were determined to be 61.25:38.73:0.02 and 53.99:34.60:11.41 for ACID and ALKALI, respectively. The optimized enzyme cocktail yielded a higher or comparable amount of reducing sugars from the hydrolysis of ACID and ALKALI when compared to that obtained using commercial cellulase mixtures. Using the commercial and easily available pure enzymes, this simple method for the in-house preparation of an enzyme cocktail specific to pretreated lignocellulose consisting of only four enzymes with a high level of hydrolysis will be helpful for achieving enzymatic saccharification in the lignocellulose-based biorefinery.     

Secretome analysis of Trichoderma reesei and Aspergillus niger cultivated by submerged and sequential fermentation processes: Enzyme production for sugarcane bagasse hydrolysis

Cellulases and hemicellulases from Trichoderma reesei and Aspergillus niger have been shown to be powerful enzymes for biomass conversion to sugars, but the production costs are still relatively high for commercial application. The choice of an effective microbial cultivation process employed for enzyme production is important, since it may affect titers and the profile of protein secretion. We used proteomic analysis to characterize the secretome of T. reesei and A. niger cultivated in submerged and sequential fermentation processes. The information gained was key to understand differences in hydrolysis of steam exploded sugarcane bagasse for enzyme cocktails obtained from two different cultivation processes. The sequential process for cultivating A. niger gave xylanase and β-glucosidase activities 3- and 8-fold higher, respectively, than corresponding activities from the submerged process. A greater protein diversity of critical cellulolytic and hemicellulolytic enzymes were also observed through secretome analyses. These results helped to explain the 3-fold higher yield for hydrolysis of non-washed pretreated bagasse when combined T. reesei and A. niger enzyme extracts from sequential fermentation were used in place of enzymes obtained from submerged fermentation. An enzyme loading of 0.7 FPU cellulase activity/g glucan was surprisingly effective when compared to the 5–15 times more enzyme loadings commonly reported for other cellulose hydrolysis studies. Analyses showed that more than 80% consisted of proteins other than cellulases whose role is important to the hydrolysis of a lignocellulose substrate. Our work combined proteomic analyses and enzymology studies to show that sequential and submerged cultivation methods differently influence both titers and secretion profile of key enzymes required for the hydrolysis of sugarcane bagasse. The higher diversity of feruloyl esterases, xylanases and other auxiliary hemicellulolytic enzymes observed in the enzyme mixtures from the sequential fermentation could be one major reason for the more efficient enzyme hydrolysis that results when using the combined secretomes from A. niger and T. reesei.     

Extracellular L-asparaginase production in solid-state fermentation by using sugarcane bagasse as support material

Abstract

L-asparaginase is an important enzyme used in the pharmaceutical and food industry, which can be produced by different microorganisms using low cost feedstocks. In this work, sugarcane bagasse (SCB) was used as support for enzyme production in solid-state fermentation (SSF) by A. terreus. Initially, the influence of the variables carbon and nitrogen sources on the enzyme production was studied following an experimental design carried out in Erlenmeyer flasks. Statistical analysis indicated the use of 0.54% of starch, 0% of maltose, 0.44% of asparagine, and 1.14% of glutamine in the medium, resulting in enzyme activity per volume of produced extract of 120.723?U/L. Then, these conditions were applied in a horizontal column reactor filled with SCB, producing 105.3?U/L of enzyme activity. Therefore, the potential of extracellular L-asparaginase enzyme production in the column reactor using sugarcane bagasse as support was demonstrated and it represents a system that can favor large scale production.     

Enhanced saccharification kinetics of sugarcane bagasse pretreated in 1-butyl-3-methylimidazolium chloride at high temperature and without complete dissolution

Dissolution of bagasse with 1-butyl-3-methylimidazolium chloride at high temperatures (110-160 °C) is investigated as a pretreatment process for saccharification and fermentation based biofuel production. Material balances are reported and used along with enzymatic saccharification data to identify optimum pretreatment conditions (150 °C for 90 min). At all pretreatment temperatures, dissolved and reprecipitated material is enriched in cellulose, has a low crystallinity and the cellulose component is easily and quantitatively hydrolysed (100%, 3h, 15 FPU). At pretreatment temperatures ≤ 150 °C, the undissolved material has only slightly lower crystallinity than the starting. At pretreatment temperatures ≥ 150 °C, the undissolved material has low crystallinity and when combined with the dissolved material has a saccharification rate and extent similar to completely dissolved material. Complete dissolution is not necessary to maximise saccharification efficiency at temperatures ≥ 150 °C.     

Extraction and characterization of wax from sugarcane bagasse and the enzymatic hydrolysis of dewaxed sugarcane bagasse

Extraction of high-value products from agricultural wastes is an important component for sustainable bioeconomy development. In this study, wax extraction from sugarcane bagasse was performed and the beneficial effect of dewaxing pretreatment on the enzymatic hydrolysis was investigated. About 1.2% (w/w) of crude sugarcane wax was obtained from the sugarcane bagasse using the mixture of petroleum ether and ethanol (mass ratio of 1:1) as the extraction agent. Results of Fourier-transform infrared characterization and gas chromatography–mass spectrometry qualitative analysis showed that the crude sugarcane wax consisted of fatty fractions (fatty acids, fatty aldehydes, hydrocarbons, and esters) and small amount of lignin derivatives. In addition, the effect of dewaxing pretreatment on the enzymatic hydrolysis of sugarcane bagasse was also investigated. The digestibilities of cellulose and xylan in dewaxed sugarcane bagasse were 18.7 and 10.3%, respectively, compared with those of 13.1 and 8.9% obtained from native sugarcane bagasse. The dewaxed sugarcane bagasse became more accessible to enzyme due to the disruption of the outermost layer of the waxy materials.     

Lipid production from Yarrowia lipolytica Po1g grown in sugarcane bagasse hydrolysate

This study investigated the possibility of utilizing detoxified sugarcane bagasse hydrolysate (DSCBH) as an alternative carbon source to culture Yarrowia lipolytica Po1g for microbial oil and biodiesel production. Sugarcane bagasse hydrolysis with 2.5% HCl resulted in maximum total sugar concentration (21.38 g/L) in which 13.59 g/L is xylose, 3.98 g/L is glucose, and 2.78 g/L is arabinose. Detoxification of SCBH by Ca(OH)₂ neutralization reduced the concentration of 5-hydroxymethylfurfural and furfural by 21.31% and 24.84%, respectively. Growth of Y. lipolytica Po1g in DSCBH with peptone as the nitrogen source gave maximum biomass concentration (11.42 g/L) compared to NH₄NO₃ (6.49 g/L). With peptone as the nitrogen source, DSCBH resulted in better biomass concentration than d-glucose (10.19 g/L), d-xylose (9.89 g/L) and NDSCBH (5.88 g/L). The maximum lipid content, lipid yield and lipid productivity of Y. lipolytica Po1g grown in DSCBH and peptone was 58.5%, 6.68 g/L and 1.76 g/L-day, respectively.