IMPACT OF HEMICELLULOSES PRE-EXTRACTION ON PULP PROPERTIES OF SUGARCANE BAGASSE (original) (raw)
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Covalent lignin-carbohydrate linkages between lignin and carbohydrates have been suggested to be a major obstacle to complete delignification of biomass feedstocks during chemical processing, e.g. pulping or enzymatic hydrolysis of the biomass to release sugars for ethanol production. The current study is aimed at developing an understanding of the structural composition and the behaviour of lignin carbohydrate complexes (LCCs) in sugarcane bagasse, a potential raw material for bio-ethanol production. Hemicelluloses were pre-extracted prior to soda AQ pulping with the aim of preserving it for further use instead of losing it in the black liquor (Value Prior Pulping or VPP). LCCs from the hemicelluloses pre-extracted soda AQ pulps as well, as non-extracted materials i.e. controls, were isolated and quantified. Mainly, two types of LCCs were identified: the xylan-lignin and glucan-lignin-xylan complexes. FTIR and GPC analyses of LCC fractions confirmed that the ester bonds of LCCs were degraded through hemicelluloses pre-extraction, leading to a significant change in their structure. This in turn resulted in more cellulose being more accessible to pulping and enzymatic hydrolysis respectively. The study showed that alkaline pre-extracted biomass materials have a more amenable structure to processing, as a result of the disruption of the unreactive LCCs in the residual lignin. Further, alkaline hemicelluloses pre-extraction in combination with soda AQ holds more promise for VPP due to reduced LCCs. This could have a positive impact in downstream processes such as bleaching.
Search for optimum conditions of sugarcane bagasse hemicellulose extraction
A process has been elaborated for one-step low lignin content sugarcane bagasse hemicellulose extraction using alkaline solution of hydrogen peroxide. To maximize the hemicellulose yields several extraction conditions were examined applying the 2 4 factorial design: H 2 O 2 concentration from 2 to 6% (w/v), reaction time from 4 to 16 h, temperature from 20 to 60 • C, and magnesium sulfate absence or presence (0.5%, w/v). This approach allowed selection of conditions for the extraction of low and high lignin content hemicellulose. At midpoint the yield of hemicellulose was 94.5% with more than 88% of lignin removed. Lignin removal is suppressed at low extraction temperatures and in the absence of magnesium sulfate. Hemicellulose in 86% yield with low lignin content (5.9%) was obtained with 6% H 2 O 2 treatment for 4 h and 20 • C. This hemicellulose is much lighter in color than samples obtained at the midpoint condition and was found suitable for subsequent enzymatic hydrolysis.
Pre-Extraction and Its Impact on the Alkaline Pulping of Bagasse
Journal of Biobased Materials and Bioenergy, 2009
the fibrous structure.le The problems associated with the presence of pith on pulping and on black liquor characteristics were studied by Kulkarni and co-workers.zo Further, commercial experience on the production of bleached bagasse kraft pulp employed the wet de-pithing process.2l Others have also studied the use of bagasse for the production of pulp and paper products.22 However, the use of bagasse for the production of high-quality pulp revealed major drawbacks due to the presence of pith, including a lower pulp yield, a higher chemical consumption, and pith-related pulp quality problems. There has always been interest in the efficient removal of pith from bagasse so that a good-quality bagasse pulp can be produced. On the other hand, bagasse pith contains high amount of hemicelluloses,23 which after removal, could be used as valuable raw materials for many value-added products, thus the concept is in harmony with the bio-refinery initiative.
Covalent lignin-carbohydrate linkages between lignin and carbohydrates have been suggested to be a major obstacle to complete delignification of biomass feedstocks during chemical processing, e.g. pulping or enzymatic hydrolysis of the biomass to release sugars for ethanol production. The current study is aimed at developing an understanding of the structural composition and the behaviour of lignin carbohydrate complexes (LCCs) in sugarcane bagasse, a potential raw material for bio-ethanol production. Hemicelluloses were pre-extracted prior to soda AQ pulping with the aim of preserving it for further use instead of losing it in the black liquor (Value Prior Pulping or VPP). LCCs from the hemicelluloses pre-extracted soda AQ pulps as well, as non-extracted materials i.e. controls, were isolated and quantified. Mainly, two types of LCCs were identified: the xylan-lignin and glucan-lignin-xylan complexes. FTIR and GPC analyses of LCC fractions confirmed that the ester bonds of LCCs wer...
Alkali extraction of hemicellulose from depithed corn stover and effects on soda-AQ pulping
BioResources
A biorefinery using the process of hemicellulose pre-extraction and subsequent pulping provides a promising way for the utilization of straw biomass and resolution of problems related to silicon. In this work, hemicellulose was extracted from depithed corn stover with sodium hydroxide solution before soda-AQ pulping. Components of the extracts were quantified by ion chromatography. The parameters (alkali concentration and temperature) affecting hemicellulose pre-extraction were optimized. The main constituent of hemicellulose in corn stover was xylan, which accounted for 18.1% of the depithed raw material. More than 90% of the xylan can be extracted under the optimal conditions: NaOH concentration of 10%, temperature of 75ºC, and time of 2h. Solid fractions after extraction were subjected to soda-AQ pulping. In comparison with control pulp obtained without extraction, it was found that alkali pre-extraction could improve the brightness and decrease kappa number of the subsequent pul...
Carbohydrate Polymers, 2014
Developing optimum treatment and separation procedures for hemicellulose components of lignocellulosic biomass could be useful in ethanol fermentation processes and obtaining pure hemicelluloses as biopolymers. Sugarcane bagasse analyses indicate that xylose is the major hemicellulose component constituting 17.7% of dry bagasse weight. In this study the effects of treatment conditions such as time, temperature and pressure on the yields of extracted hemicelluloses were studied. The optimum conditions were achieved at 180 • C for 30 min and 1 MPa pressure, with the yield of xylose reaching to 85% and the concentrations of sugar degradation products such as HMF and furfural remaining minimal at 0.95 and 0.07 g/L, respectively. Further, isolation of hemicelluloses from extracted hemicelluloses solutions was performed using Alfa Laval M20 membrane filtration system in two steps: (1) concentration of high molar mass hemicelluloses by ultrafiltration; and (2) separation of low molar mass hemicelluloses and oligomeric sugars by nanofiltration. The isolated hemicelluloses with the optimum pretreatment conditions were characterized by FT-IR and 13 C NMR techniques, resulting in agreement with typical spectra of xylan-type hemicelluloses.
Comparative Study of Hemicelluloses Obtained by Graded Ethanol Precipitation from Sugarcane Bagasse
Journal of Agricultural and Food Chemistry, 2009
The sequential treatment of dewaxed sugarcane bagasse with H 2 O and 1 and 3% NaOH at a solid to liquid ratio of 1:25 (g mL -1 ) at 50°C for 3 h yielded 74.9% of the original hemicelluloses. Each of the hemicellulosic fractions was successively subfractionated by graded precipitation at ethanol concentrations of 15, 30, and 60% (v/v). Chemical composition, physicochemical properties, and structures of eight precipitated hemicellulosic fractions were elucidated by a combination of sugar analysis, nitrobenzene oxidation of bound lignin, molecular determination, Fourier transform infrared (FT-IR), 1 H and 13 C nuclear magnetic spectroscopies, and thermal analysis. The results showed that the sequential treatments and graded precipitations were very effective on the fractionation of hemicelluloses from bagasse. Comparison of these hemicelluloses indicated that the smaller sized and more branched hemicelluloses were extracted by the hot water treatment; they are rich in glucose, probably originating from R-glucan and pectic polysaccharides. The larger molecular size and more linear hemicelluloses were dissolved by the alkali treatment; they are rich in xylose, principally resulting from L-arabino-(4-O-methylglucurono)-D-xylans. In addition, noticeable differences in the chemical composition and molecular weights were observed among the graded hemicellulosic subfractions from the water-soluble and alkali-soluble hemicelluloses. The Ara/Xyl ratio increased with the increment of ethanol concentration from 15 to 60%, and the arabinoxylans with higher Ara/Xyl ratios had higher molecular weights. There were no significant differences in the structural features of the precipitated hemicellulosic subfractions, which are mainly constituted of L-arabino-(4-O-methyl-D-glucurono)xylan, whereas the difference may occur in the distribution of branches along the xylan backbone.
The extraction of hemicelluloses prior to pulping is an attractive process to be incorporated in the pulp and paper mills to generate valuable by-products such as xylose and xylo-oligomers in addition to core products. This paper investigates the impact of xylan extraction by dilute acid on cooking conditions, pulp yield and properties during kraft and soda-AQ pulping of Eucalyptus grandis wood chips. Modified soda-AQ pulping of the wood chips from which 21.3% of xylan was extracted using a low alkali charge maintained the pulp yield, viscosity and kappa number of non-extracted wood chips. The combination of these processes resulted in chemical reduction while increasing the digester capacity by 12%. Due to extraction, the handsheet properties were reduced, especially the tear index. The degree of hemicellulose pre-extraction and pulping conditions can be optimized based on final paper application.
Extraction of Cellulose from Sugarcane Bagasse Optimization and Characterization
Advances in Materials Science and Engineering
In this study, cellulose was extracted from sugarcane bagasse (SCB) through a convenient five-step treatment, and procedures were performed. During the alkaline curing process of the extraction of cellulose, NaOH has a concentration of (0.5, 1.5, 2.75, and 4%) and the extraction time (15, 30, and 45 min) at a constant temperature of 120°C were taken as variables and perfectly optimized by response surface methodology (RSM) for cellulose with the highest product. The optimum conditions were found to be 2.75% NaOH, 120°C, and 45 min with a cellulose yield of 73.71 ± 0.67% cellulose, 17.22 ± 0.82% hemicellulose, and 9.07 ± 0.95% lignin. Though most of the lignin was eliminated during the alkaline and dilute acid pretreatment process, the remaining lignin was removed by a solution treatment of 4% NaOH, and 21.92% H2O2 at 121°C for 44.97 min where the cellulose yield was found as 89.75 ± 0.64%, hemicellulose was 6.15 ± 0.83%, and lignin was 2.65 ± 0.66%. Morphological analysis revealed t...
The alkaline and acid preextraction of giant bamboo (Bambusa balcooa Roxburgh), grown in South Africa, before kraft and soda-anthraquinone (AQ) pulp-ing was in focus and the effects of NaOH concentration, temperature, and time on hemicelluloses extraction were studied by means of a statistical experimental design. The NaOH concentration exerted the strongest influence, solubilizing up to 20.4% of the available xylan with 2.0 M NaOH at 90°C for 240 min. The optimal extraction condition was achieved with 1 M NaOH at 90°C for 240 min, in the course of which 13.6% of the xylan was removed; the screened pulp yield was 50.4% without viscosity reduction , whereas the burst index of the handsheets was even improved. In the case of dilute acid preextraction before soda-AQ pulping, 11.3% xylan could be removed without affecting the pulp quality. The viscosity of the pulp was even better than that of pulps from nonextracted bamboo. The biorefinery approach, alkaline preextraction in combination with kraft pulping, is superior to the approach, acid prehydrolysis/soda-AQ pulping.