Adilson R. Gonçalves

Industrial-scale steam explosion pretreatment of sugarcane straw for enzymatic hydrolysis of cellulose for production of second generation ethanol and value-added products

Steam explosion at 180, 190 and 200°C for 15min was applied to sugarcane straw in an industrial sugar/ethanol reactor (2.5m(3)). The pretreated straw was delignificated by sodium hydroxide and hydrolyzed with cellulases, or submitted directly to enzymatic hydrolysis after the pretreatment. The pretreatments led to remarkable hemicellulose solubilization, with the maximum (92.7%) for pretreatment performed at 200°C. Alkaline treatment of the pretreated materials led to lignin solubilization of 86.7% at 180°C, and only to 81.3% in the material pretreated at 200°C. All pretreatment conditions led to high hydrolysis conversion of cellulose, with the maximum (80.0%) achieved at 200°C. Delignification increase the enzymatic conversion (from 58.8% in the cellulignin to 85.1% in the delignificated pulp) of the material pretreated at 180°C, but for the material pretreated at 190°C, the improvement was less remarkable, while for the pretreated at 200°C the hydrolysis conversion decreased after the alkaline treatment.

Hydroxymethylation and oxidation of Organosolv lignins and utilization of the products

Organosolv lignins obtained from Eucalyptus grandis, sugarcane bagasse and Picea abies by Acetosolv, Formacell and Organocell processes were characterized, fractionated and converted to hydroxymethylated and oxidized products. The reactivity of lignins with formaldehyde did not improve significantly with the fractionation. Both eucalyptus Acetosolv (EAc) and eucalyptus Formacell (EFo) lignins retained high heterogeneity in relation to the molecular weight distribution but not in relation to structural units. The temperatures of the exothermic peaks and the apparent activation energies for the cross-linking are different for hydroxymethylated lignins and phenol, with similar cure temperatures of the resols. Chemical oxidation using cobalt(II) and manganese(II) salts furnished oxidized lignins with improved chelating properties. These chelating agents can remove up to 14% of Mn present in pulps, decreasing the peroxide consumption in the bleaching process. The products obtained can be also used as oxidized phenols and controlled-release matrices. Oxidation of Acetosolv bagasse lignin with polyphenol oxidase furnishes lignins with chelating capacity 110% higher than that of original lignin.

Mass balance of pilot-scale pretreatment of sugarcane bagasse by steam explosion followed by alkaline delignification.

Five pilot-scale steam explosion pretreatments of sugarcane bagasse followed by alkaline delignification were explored. The solubilised lignin was precipitated with 98% sulphuric acid. Most of the pentosan (82.6%), and the acetyl group fractions were solubilised during pretreatment, while 90.2% of cellulose and 87.0% lignin were recovered in the solid fraction. Approximately 91% of the lignin and 72.5% of the pentosans contained in the steam-exploded solids were solubilised by delignification, resulting in a pulp with almost 90% of cellulose. The acidification of the black liquors allowed recovery of 48.3% of the lignin contained in the raw material. Around 14% of lignin, 22% of cellulose and 26% of pentosans were lost during the process. In order to increase material recovery, major changes, such as introduction of efficient condensers and the reduction in the number of washing steps, should be done in the process setup.

Eucalyptus organosolv lignins: study of the hydroxymethylation and use in resols

Abstract Lignins obtained from Acetosolv and Formacell delignification of Eucalyptus grandis chips (EAc and EFo, respectively) were reacted with formaldehyde in alkaline medium. The hydroxymethylation was followed by dynamic DSC, to determine the relative reactivity of both lignins. TGA results showed that hydroxymethylated lignins are thermally stable up to 250°C, while the original lignins are stable until 200°C. The synthesis of resols containing EAc and EFo lignins were carried out following multivariate factorial designs (24−1). The effects of four parameters were studied on the synthesis time and on the final viscosity (η). The NaOH:phenolics ratio and the solid content have the more significant effects on the synthesis time and η, for both lignins. Shorter synthesis time is obtained increasing the lignin:phenol ratio from 2:3 to 1:1 for EAc and EFo lignin, but the effect of the HCHO:phenolics ratio is important only for resols containing EFo. For this study, the multivariate experimental design is more adequate than an univariate method, since there is a large interaction between the synthesis parameters as demonstrated by the second order effects.

Carboxymethylcellulose Obtained by Ethanol/Water Organosolv Process Under Acid Conditions

Sugar cane bagasse pulps were obtained by ethanol/water organosolv process under acid and alkaline conditions. The best condition of acid pulping for the sugarcane bagasse was 0.02 mol/L sulfuric acid at 160°C, for 1 h, whereas the best condition for alkaline pulping was 5% sodium hydroxide (base pulp) at 160°C, for 3 h. For the residual lignin removal, the acid and alkaline pulps were submitted to a chemical bleaching using sodium chlorite. Pulps under acid and alkaline conditions bleached with sodium chlorite presented viscosities of 3.6 and 7.8 mPa·s, respectively, and μ-kappa numbers of 1.1 and 2.4, respectively. The pulp under acid condition, bleached with sodium chlorite was used to obtain carboxymethylcellulose (CMC). CMC yield was 35% (pulp based), showing mass gain after the carboxymethylation reaction corresponding to 23.6% of substitution or 0.70 groups −CH2 COONa per unit of glucose residue. The infrared spectra showed the CMC characteristic bands and by the infrared technique it was possible to obtain a substitution degree (0.63), similar to the substitution degree calculated by mass gain (0.70).

Identifying the origin of lignins and monitoring their structural changes by means of FTIR-PCA and -SIMCA

Abstract Lignins from sugarcane bagasse and eucalyptus, isolated respectively from soda and kraft liquors by precipitation with HCl or H 2 SO 4 , have been investigated together with samples of lignins isolated after organosolv pulping. Sugarcane bagasse lignin precipitated by HCl underwent oxidation by O 2 in aqueous NaOH. The reaction products, the oxidized lignin (reprecipitated with HCl) and the soluble products (isolated by evaporation) formed two other groups of samples. Fourier transform infra-red (FTIR) spectra of 49 of these lignins samples in KBr disks were recorded and analysed by principal component analysis (PCA) and statistical isolinear multicomponent analysis (SIMCA). After normalization of the spectra by dividing the absorbance value at a certain wavenumber by the absorbance value at 1510 cm −1 , PCA analysis using 597 data points collected between 1950 and 800 cm −1 showed that the first two principal components describe most of the total spectral variance. The plot of these two principal components allowed the lignins to be grouped according to their isolation (kraft, alkaline pulping or organosolv), but no difference could be observed when the lignins were isolated from liquor by precipitation with HCl or H 2 SO 4 . Furthermore, the method allows a very good separation of the acetylated samples and can be used as a tool to rapidly identify the origin of lignin samples or to monitor their structural changes.

Evaluation of Panus tigrinus in the delignification of sugarcane bagasse by FTIR-PCA and pulp properties

Abstract Seven strains of Panus tigrinus were grown, without any additional carbon source, on sugarcane bagasse for 10 days in a semi-solid state fermentation. The production of MnP, LiP and Lac by fungi were correlated with the efficiency of delignification process in bagasse after organosolv pulping with aqueous acetic acid. Analysis of decayed sugarcane bagasse by FTIR indicated a correlation between lignin modification and pulp properties in some strains, in such a way that the more the lignin modifies, the more the pulp properties improve. This correlation became more evident after PCA treatment of the spectra. The absorption at 1000 cm −1 , corresponding to C–O bonds, determines the separation of the samples in the principal component plot. PCA of FTIR spectra can be used together with activity values to predict pulp properties of decayed bagasse samples.

Ceriporiopsis subvermispora used in delignification of sugarcane bagasse prior to soda/anthraquinone pulping.

Sugarcane bagasse was pretreated with the white-rot fungus Ceriporiopsis subvermispora for 30 d of incubation. The solid-state fermentation of 800 g of bagasse was carried out in 20-L bioreactors with an inoculum charge of 250 mg of fungal mycelium/kg of bagasse. The oxidative enzymes manganese peroxidase (MnP), lignin peroxidase (LiP), and laccase (Lac) and the hydrolytic enzyme xylanase (Xyl) were measured by standard methods and related to the funguss potential for delignification. Among the lignocellulolytic assayed enzymes, Xyl was detected in larger quantity (4478 IU/kg), followed by MnP (236 IU/kg). LiP and Lac were not detected. The results of chemical analysis and mass component loss showed that C. subvermispora was selective to lignin degradation. Pretreated sugarcane bagasse and control pulps were obtained by soda/anthraquinone (AQ) pulping. Pulp yields, kappa number, and viscosity of all pulps were determined by chemical analysis of the samples. Yields of soda/AQ ranged from 46 to 54%, kappa numbers were 15-25, and the viscosity ranged from 3.6 to 7 cP for pulps obtained from pretreated sugarcane bagasse.

Integrated processes for use of pulps and lignins obtained from sugarcane bagasse and straw: a review of recent efforts in Brazil.

Sugarcane bagasse and straw can be converted into pulps, oils, controlled-release formulations, chelating agents, and composites. This article reviews bagasse and straw conversion efforts in Brazil. Laboratory-scale processes were developed aiming at the integral use of these biomass byproducts. Organosolv pulping and oxidation of lignin are the most promising processes for the rational use of sugarcane residues. Fungal pretreatment and spectroscopic characterization are also discussed.

Hydrogenolysis of lignins: influence of the pretreatment using microwave and ultrasound irradiations.

Hydrolytic eucalyptus lignin was converted to oils by hydrogenolysis. The lignin was obtained by acid hydrolysis of eucalyptus chips from two semi-industrial sources in Brazil: FTI and Coalbra. Hydrogenolysis was performed in an 1-L reactor using lignin/water ratio 1/4 (w/v), pH 9 (adjusted with NaOH), 0.1 g sodium formate/g lignin, 20 MPa (argon pressure) at 280°C for 15 min. After reaction, the products were filtered and the solids extracted with chloroform/ethanol 3/1 (v/v). The solvent was evaporated from the organic phase and a dark oil was obtained. The solid remaining after extraction was weighed to calculate the conversion. Without pretreatment conversions were 41.3 and 47.9% for Coalbra and FTI, respectively. The oil yields were 22.7–27.6% for Coalbra and FTI, respectively. Using microwave pretreatment (30 min of irradiation at 490 W) the conversions were 41.6–50.5% and the oil yields increased slightly to 25.2–31.4%. The polymeric chains in the lignin breakdown due to the action of water near the boiling point under microwave irraditation. On the other hand, by using ultrasound (30 min at 50°C in a ultrasound bath of 25 kHz and 0.8 W/cm2) the conversions were 35.2–46.9% and oil yields were 22.0–27.1%. Ultrasound favors the formation of radicals that probably caused the reticulation of lignins, decreasing the conversion and yield. Oils analyzed by infrared spectroscopy showed an increase in C=O bond intensities, compared with the original lignins.