Cellulose Crystallinity Index Research Articles

Distinct polymer extraction and cellulose DP reduction for complete cellulose hydrolysis under mild chemical pretreatments in sugarcane

In this study, liquid hot water (LHW) and chemical (H2SO4, NaOH, CaO) pretreatments were performed in Saccharum species including sugarcane bagasse. In comparison, the LHW and CaO pretreatments significantly enhanced biomass enzymatic hydrolysis, leading to much high bioethanol yield obtained at 19% (% dry matter) with an almost complete hexoses-ethanol conversion in the desirable So5 bagasse sample. Despite the LHW and CaO are distinctive for extracting hemicellulose and lignin, both pretreatments largely reduced cellulose degree of polymerization for enhanced lignocellulose enzymatic saccharification. Further chemical analysis indicated that the pretreated So5 sample had much lower cellulose crystalline index, hemicellulosic Xyl/Ara and lignin S/H ratio than those of other biomass samples, which explained that the So5 had the highest bioethanol yield among Saccharum species. Therefore, a mechanism model was proposed to elucidate how mild pretreatments could enhance biomass enzymatic saccharification for a high bioethanol production in the desirable sugarcane bagasse.

Impact of biomass feedstock variability on acid-catalyzed alcoholysis performance

Alcoholysis was an efficient way for liquefying lignocellulosic biomass into valuable platform chemicals. In this study, the impact of feedstock types on the acid-catalyzed alcoholysis performance was systematically investigated by comparing the alcoholysis ratio, product distribution and production of main products. Component analysis showed that three major chemical components could be efficiently degraded, further, hemicellulose and lignin were prone to be decomposed than cellulose. The time dependent alcoholysis ratio evolution was highly related to the feedstock types with the variation in lignin content and cellulose crystallinity index (CrI). The alcoholysis product distributions also varied significantly with different feedstocks according to the GC–MS analysis results. Ethyl levulinate (EL), furfural and ethyl p-hydroxybenzoate were identified as the major components in the products. The high mass yield 12.4% of EL was obtained from corn stover, and it was highly correlated to the cellulose content and CrI. The maximum mass yield of furfural was produced from wheat straw while a considerable amount of ethyl p-hydroxybenzoate was typically produced from poplar wood. With the comprehensive understanding of the impact of feedstock variability on the alcoholysis performance, our study could give an empirical evidence for product-oriented feedstock selection in biofuels and chemicals production.

Ultrasound-assisted alkaline pretreatment to intensify enzymatic saccharification of Crotalaria juncea using a statistical method

Sunn hemp as a non-woody fiber crop was selected to determine the effect of ultrasound-assisted alkali pretreatment on enzymatic hydrolysis. We hypothesized that ultrasound-assisted alkali pretreatment (US-NaOH) was more efficient than alkali pretreatment alone; maximum fermentable sugars were released in US-NaOH-pretreated biomass by enzymatic hydrolysis. In this study, sunn hemp was pretreated with NaOH and US-NaOH at 121 °C. A higher cellulose content of 67% was obtained in US-NaOH-pretreated biomass (1% NaOH, 10-min sonication, 121 °C) as compared with that of the alkali-pretreated biomass. After ultrasound-assisted alkaline pretreatment, the crystallinity index of cellulose and the solubilization of pentose and lignin increased from 39 to 53%, leading to a significant increase in enzyme accessibility to cellulose to release reducing sugars. Scanning electron microscopy showed that the biomass underwent erosion after ultrasound pretreatment. Response surface methodology was chosen to study the individual effects of variables on enzymatic hydrolysis and their inter-dependence. The quantity of reducing sugars released was optimized using a response surface methodology, and the experimental results with optimized process variables gave 5.17 mg/mL glucose and 2.08 mg/mL xylose.

Understanding the influences of different pretreatments on recalcitrance of Populus natural variants

Four different pretreatment technologies were applied to two Populus natural variants and the effects of each pretreatment on glucose release were compared. Physicochemical properties of pretreated biomass were analyzed by attenuated total reflection Fourier transform infrared spectroscopy, gel permeation chromatography, and cross polarization/magic angle spinning carbon-13 nuclear magnetic resonance techniques. The results revealed that hemicellulose and lignin were removed to different extents during various pretreatments. The degree of polymerization of cellulose was decreased in the order of alkali > hydrothermal > organosolv > dilute acid pretreatment. Cellulose crystallinity index was slightly increased after each pretreatment. The results also demonstrated that organosolv pretreatment resulted in the highest glucose yield. Among the tested properties of Populus, degree of polymerization of cellulose was negatively correlated with glucose release, whereas hemicellulose and lignin removal, and cellulose accessibility were positively associated with glucose release from the two Populus natural variants.

Improvement to the solubility and reactivity of purified bamboo fibers using a combined chemi-mechanical process

Bamboo fibers exhibit poor solubility and reactivity because of the aggregational structure of cellulose macro-molecules in fiber cell walls. It has been shown that more free hydroxyl groups on cellulose molecules can be exposed via fibrillation of the fiber walls during a PFI beating process. The changes in fiber characteristics, such as the fibrillation degree, water retention value (WRV), and crystallinity, were analyzed. The results showed that the fiber fibrillation increased from 0.781% to 1.072%, and the WRV increased from 112.8% to 213.6% during the beating process, indicating that a fibrillation effect was present in the bamboo fiber walls that corresponded to an incremental change in the degree of mechanical pretreatment. The saturated solubility value of the treated fibers in an alkali/urea solvent system at low temperature increased from 0.22 wt.% to 2.69 wt.% with an incremental change in the degree of mechanical pretreatment. After high-revolution PFI beating, the cellulose crystallinity index of the samples decreased from 66.4% to 50.0%, but the intrinsic viscosity changed only slightly. The oxidation degree of the cellulose in the treated samples increased from 0.85 mol/AGU to 1.03 mol/AGU, which suggested that the reagent accessibility and chemical reaction performance of the bamboo fibers were both improved.

Structural and Thermal Stability Changes of Rice Straw Fibers during Anaerobic Digestion

Rice straw fibers are potential raw materials that can be used to produce biogas and reinforcing fibers for composites. In order to ascertain the effects of anaerobic digestion on the structural properties of the fibers, the structure of fibrous residuals with different digestion time, including 0, 10, 20, and 30 days, were investigated. The normalized biogas production volume was 224 mL/g volatile solid of substrate, of which the methane content was about 50%. Fiber detergent analyses of the straw before and after 10 days digestion indicated that the cellulose levels increased from 34.3% to 41.3%, and cellulose crystallinity index ranged from 44.9% to 49.9%, respectively. After the rice straw had been digested for 30 days, the cellulose and hemicelluloses of the rice straw were partially degraded; the crystallinity index of the cellulose decreased from 44.9% to 40.1% based on XRD analyses, and the amount of hydroxyl groups were observed to decrease based on FT-IR analyses. Consequently, the polarity and hygroscopicity of the rice straw fibers were speculated to be lowered based on these observed changes. Furthermore, the relative amount of lignin in the straw residuals increased as digestion time increased, which increased the thermal stability of the resulting fibers. As a result of anaerobic digestion, the properties of the rice straw fibers for their use in plastic composites were enhanced.

The degradation and saccharification of microcrystalline cellulose in aqueous acetone solution with low severity dilute sulfuric acid

Abstract Hydrolysis properties of microcrystalline cellulose (MCC) in different aqueous polar aprotic solvents with low severity sulfuric acid were compared. Comparing to other polar aprotic solvents, acetone had better performance in hydrolysis of MCC. The effects of reaction conditions on the degradation and saccharification of MCC were investigated. The results indicated some glucose was converted to fructose by isomerization during the degradation process, but fructose was more easily degraded to by-products in subcritical system, which resulted in the decline of saccharification yield. After MCC was treated with 80 wt% acetone solution with 0.1 wt% H2SO4, solid-liquid ratio of 1:10 (g/g) at 180 °C for 60 min, its weight loss rate and saccharification yield could achieve 58% and 71%, respectively The specific surface area of MCC increased in this process, although the crystallinity index of cellulose increased. Furthermore, 72.9% of levulinic acid and almost all of the HMF and furfural in the hydrolysate could be extracted by ethyl acetate. Remarkably, the recovered sugars could be used as the carbon source for succinic acid production.

Deterioration effects of wet environments and brown rot fungus Coniophora puteana on pine wood in the archaeological site of Biskupin (Poland)

The archaeological site of Biskupin (Poland) is a prehistoric settlement dating to the 8th century BC, situated on a marshy island. Excavations started in 1934 and a considerable number of wooden artifacts were found in the lake water. Unfortunately, during many years of archaeological excavations, wooden remains deposited in the trenches were exposed to degradation and underwent considerable decomposition. Among the main causes of wood degradation, fungi and bacteria were the most destructive ones.The chemical effects induced by fungi and bacteria on wood are not well-known or studied. Here we present the investigation of a set of pine wood samples (Pinus sylvestris) buried in the Biskupin site, with the aim of reproducing the burial conditions of the original archaeological wood. Two monitoring stations (wet peat and lake water) were chosen and the samples were then removed from these burial environments after four and ten years. After removal, the samples were exposed to laboratory-controlled attack by the brown rot fungus Coniophora puteana. The final aim was to evaluate the effects of fungal activity on the wood substrates with different degrees of natural degradation. The study is part of an experiment designed to evaluate the short-term effects of the in situ preservation strategy adopted for the Biskupin archaeological woods.Various techniques were used to assess the physical and chemical degradation of the wood. The morphological changes induced by the exposure to the burial environment and by the action of the fungi were investigated using scanning electron microscopy (SEM). The chemical state of the wood was evaluated by using infrared spectroscopy (FTIR), analytical pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS) and XRD spectroscopy.Fungal action caused the depletion of polysaccharides resulting in mass loss and the FTIR spectra of the wood samples highlighted that cellulose was more degraded with respect to hemicelluloses. This trend correlated with an increase in the relative abundance of furans, which are among the main pyrolysis products of polysaccharides. Fungal attack also induced oxidation of lignin and an increase in the crystallinity index of cellulose, which points towards a preferential metabolisation of amorphous cellulose. The overall results highlighted that the burial in these wet environments caused changes mostly in the hemicelluloses, whereas the fungal attack was mainly directed to cellulose degradation.

Recycled ionic liquid 1-ethyl-3-methylimidazolium acetate pretreatment for enhancing enzymatic saccharification of softwood without cellulose regeneration

In this work, pretreatment of wood meals using a recycled ionic liquid (IL), 1-ethyl-3-methylimidazolium acetate ([Emim]Ac), enhanced glucose liberation by enzymatic saccharification, without dissolution of cellulose and lignin. In contrast, previous studies on IL pretreatment have mostly focused on lignocellulosic dissolution to regenerate cellulose and removing lignin. Softwood (Cryptomeria japonica) was pretreated with [Emim]Ac at 60–100 °C for 2–8 h without collecting regenerated cellulose. The pretreatment did not have a strong effect on wood component dissolution (weight of residues: 91.7–98.8%). The residues contained relatively high amounts of lignin (26.6–32.6%) with low adsorption of [Emim]Ac (0.9–2.7%). Meanwhile, the crystallinity index (C r I) of cellulose in the wood was significantly reduced by pretreatment, from 50.9% to 28.4–37.1%. In spite of the high lignin contents in the residues, their glucose liberation values by enzymatic saccharification using a cellulase mixture were 3–16 times greater than that of untreated wood. A good correlation was found between the saccharification effectiveness of pretreated samples and the C r I. Although lignin dissolved in [Emim]Ac continued to accumulate after repeated use of [Emim]Ac, the pretreatment was found to be effective for three consecutive cycles without the need to remove the dissolved materials.

The effect of liquid hot water pretreatment on the chemical\u2013structural alteration and the reduced recalcitrance in poplar

BackgroundHydrothermal pretreatment using liquid hot water (LHW) is capable of substantially reducing the cell wall recalcitrance of lignocellulosic biomass. It enhances the saccharification of polysaccharides, particularly cellulose, into glucose with relatively low capital required. Due to the close association with biomass recalcitrance, the structural change of the components of lignocellulosic materials during the pretreatment is crucial to understand pretreatment chemistry and advance the bio-economy. Although the LHW pretreatment has been extensively applied and studied, the molecular structural alteration during pretreatment and its significance to reduced recalcitrance have not been well understood.ResultsWe investigated the effects of LHW pretreatment with different severity factors (log R0) on the structural changes of fast-grown poplar (Populus trichocarpa). With the severity factor ranging from 3.6 to 4.2, LHW pretreatment resulted in a substantial xylan solubilization by 50–77% (w/w, dry matter). The molecular weights of the remained hemicellulose in pretreated solids also have been significantly reduced by 63–75% corresponding to LHW severity factor from 3.6 to 4.2. In addition, LHW had a considerable impact on the cellulose structure. The cellulose crystallinity increased 6–9%, whereas its degree of polymerization decreased 35–65% after pretreatment. We found that the pretreatment severity had an empirical linear correlation with the xylan solubilization (R2 = 0.98, r = + 0.99), hemicellulose molecular weight reduction (R2 = 0.97, r = − 0.96 and R2 = 0.93, r = − 0.98 for number-average and weight-average degree of polymerization, respectively), and cellulose crystallinity index increase (R2 = 0.98, r = + 0.99). The LHW pretreatment also resulted in small changes in lignin structure such as decrease of β-O-4′ ether linkages and removal of cinnamyl alcohol end group and acetyl group, while the S/G ratio of lignin in LHW pretreated poplar residue remained no significant change compared with the untreated poplar.ConclusionsThis study revealed that the solubilization of xylan, the reduction of hemicellulose molecular weights and cellulose degree of polymerization, and the cleavage of alkyl–aryl ether bonds in lignin resulted from LHW pretreatment are critical factors associated with reduced cell wall recalcitrance. The chemical–structural changes of the three major components, cellulose, lignin, and hemicellulose, during LHW pretreatment provide useful and fundamental information of factors governing feedstock recalcitrance during hydrothermal pretreatment.

Structural features influential to enzymatic hydrolysis of cellulose-solvent-based pretreated pinewood and elmwood for ethanol production.

Dissolution of lignocelluloses in N-methylmorpholine-N-oxide (NMMO or NMO)at moderate conditions, e.g., 120°C for 3h under atmospheric pressure, and regeneration with water, is among the most effective nonderivatization pretreatment for the improvement of enzymatic hydrolysis and ethanol production. The effects of the pretreatment on two different types of wood, hardwood elm and softwood pine, were compared via physicochemical structural analyses, i.e., FTIR, XRD, SEM, TGA, and enzyme adsorption techniques, to relate their properties to the extent of enzymatic conversion. After the pretreatment, cellulose was highly recovered and characterized to be mainly cellulose II and amorphous cellulose, with lower cellulose crystallinity index, higher thermal stability, and more favorable surface features for hydrolysis, compared to native woods. Moreover, the strength of enzyme binding onto the lignocelluloses, which was directly related to the enzymatic hydrolysis rate, increased by 57% and 164% for pinewood and elmwood, respectively. The highest total reducing sugars yield for untreated pinewood was 9.8% (74mg/g-substrate) and improved to 58.5% (330mg/g-substrate) after the pretreatment, whereas the corresponding values for elmwood were 14.7% (104mg/g-substrate) vs. 51.4% (274mg/g-substrate). Furthermore, maximum ethanol theoretical yields of 63.5 and 41.4% were obtained from pinewood and elmwood by Saccharomyces cerevisiae and Mucor indicus, respectively.

Extended light exposure increases stem digestibility and biomass production of switchgrass.

Switchgrass is a photoperiod-sensitive energy grass suitable for growing in the marginal lands of China. We explored the effects of extended photoperiods of low-irradiance light (7 μmol·m-2·s-1, no effective photosynthesis) on the growth, the biomass dry weight, the biomass allocation, and, especially, the stem digestibility and cell wall characteristics of switchgrass. Two extended photoperiods (i.e., 18 and 24 h) were applied over Alamo. Extended light exposure (18 and 24 h) resulted in delayed heading and higher dry weights of vegetative organs (by 32.87 and 35.94%, respectively) at the expense of reducing the amount of sexual organs (by 40.05 and 50.87%, respectively). Compared to the control group (i.e., natural photoperiod), the yield of hexoses (% dry matter) in the stems after a direct enzymatic hydrolysis (DEH) treatment significantly increased (by 44.02 and 46.10%) for those groups irradiated during 18 and 24 h, respectively. Moreover, the yield of hexoses obtained via enzymatic hydrolysis increased after both basic (1% NaOH) and acid (1% H2SO4) pretreatments for the groups irradiated during 18 and 24 h. Additionally, low-irradiance light extension (LILE) significantly increased the content of non-structural carbohydrates (NSCs) while notably reducing the lignin content and the syringyl to guaiacyl (S/G) ratio. These structural changes were in part responsible for the observed improved stem digestibility. Remarkably, LILE significantly decreased the cellulose crystallinity index (CrI) of switchgrass by significantly increasing both the arabinose substitution degree in xylan and the content of ammonium oxalate-extractable uronic acids, both favoring cellulose digestibility. Despite this LILE technology is not applied to the cultivation of switchgrass on a large scale yet, we believe that the present work is important in that it reveals important relationships between extended day length irradiations and biomass production and quality. Additionally, this study paves the way for improving biomass production and digestibility via genetic modification of day length sensitive transcription factors or key structural genes in switchgrass leaves.

Post-sulfonation of cellulose nanofibrils with a one-step reaction to improve dispersibility

Cellulose nanofibrils (CNF) were sulfonated and the dispersion quality was compared to unfunctionalized and 2,2,6,6-tetramethylpiperdine-1-oxyl radical (TEMPO) post-oxidation treatment of existing CNF (mechanically fibrillated pulp). A post-sulfonation treatment on existing CNF in chlorosulfonic acid and dimethylformamide (DMF) resulted in sulfonated CNF that retained a fibril-like morphology. There was a small decrease in the cellulose crystallinity index for the sulfonated CNF, but this was much lower than the reported regioselective oxidative bisulfite pretreatment method used to make sulfonated CNF. The current approach was extremely quick, and 5min of reaction time was sufficient to result in significant improvements in dispersibility compared to unfunctionalized CNF. The sulfonated CNF and TEMPO oxidized CNF had better dispersibility compared to the unfunctionalized CNF when dispersed in DMF and water, and in many cases the sulfonated CNF had better dispersibility than the TEMPO CNF. It was found that when CNF was dispersed in DMF the TEMPO CNF formed carboxyl dimethylammonium groups, while the sulfonated CNF formed formate groups.

Length-controlled cellulose nanofibrils produced using enzyme pretreatment and grinding

The length of cellulose nanofibrils (CNFs) is a significant parameter for various applications. The goal of this research was to employ a fabrication method to produce length-controlled CNFs; the chosen technique was enzy-grinding (enzyme pretreatment followed by mechanical grinding). Here, we presented the results of the optimization of the diameter and length, the characterization of the properties of CNFs and nanofilms prepared using these fibrils. The cellulose morphology, crystallinity index (CrI), chemical structure, and thermal stability were investigated as functions of the enzyme loading and hydrolysis time. The results showed that enzy-grinding could effectively reduce the diameter and length of cellulose fibrils. The average diameter was about 8.6 ± 3.6 nm, and the length could be controlled over the range from 0.76 ± 0.38 μm to ≥ 4 μm (i.e. aspect ratios from 43 to ≥ 328). After the grinding process, the CNFs maintained high thermal stability and no change in the chemical structure compared to the original pulp. The transmittance and mechanical properties of the CNF films were strongly dependent on the fibril length. The fabrication of length-controlled CNFs using the enzy-grinding process is meaningful and significant research which could be relevant to the optimization of such materials for various applications.

Production of Microfibrillated Cellulose by Novel Continuous Steam Explosion Assisted Chemo-Mechanical Methods and Its Characterizations

In this study, microfibrillated cellulose (MFC) was successfully isolated with different time treatments of steam explosion, which were combined with chemo-mechanical stages. The objectives of this study were to isolate and characterize MFC obtained from steam explosion—assisted novel chemo-mechanical methods, and to investigate the effects of different steam explosion times on obtained MFC. Characterizations used were SEM, TEM, PSA, GC–MS, EDS, XRD, FTIR, and STA. The result of this study showed an optimal diameter range of MFC samples was between 23.45 and 77.65 nm at 1 h steam explosion time. However, MFC fibers were aggregated until its particle size distribution by number was about 645.83 nm. That lignocellulose MFC comprised C, N, and O with a dramatic decrease of Si. Most of the samples had many transmittance peaks, indicating the presence of cellulose with –OH, –CH2, C–H, and C–O functional groups whereas IR peaks designated to hemicellulose and lignin were almost absent. The presence of n-heptadecanol-1; n-nonadecanol-1; n-nonadecanol; hexadecanoic acid, ethyl ester; ethyl oleate; and octadecanoic acid, ethyl ester was linked with existance of cellulose and cementing agents (hemicellulose and lignin). There was an increase of cellulose crystallinity along with the increase in steam explosion time. Native cellulose or cellulose I was the initial nature of obtained MFC. The decrease of thermal stability of hemicellulose was correlated with acid treatment and acetyl groups, while the increase of cellulose thermal stability was in accordance with the increase of cellulose crystallinity index.

Ultrasound assisted alkaline pretreatment to enhance enzymatic saccharification of grass clipping

Grass clipping, a cellulose-rich raw material, has great potential to produce biofuels, but must be firstly hydrolyzed to liberate fermentable sugars. In this study, grass clipping was pretreated with ultrasound (US), Ca(OH)2, NaOH, US-Ca(OH)2 and US-NaOH at relatively low temperature to enhance its enzymatic hydrolysis. The solubilization of hemicellulose and lignin, and crystallinity index of cellulose increased after US-alkaline pretreatment, leading to a significant increase of enzyme accessibility to cellulose. Compared with another four pretreatments, US-Ca(OH)2 pretreatment of grass clipping showed the best improvement for reducing sugar yield. X-ray diffraction (XRD) determination and scanning electron microscope (SEM) observation showed that the crystallinity index of grass clipping increased and the grass clipping surface suffered from serious erosion after US-Ca(OH)2 pretreatment. Then, the operating conditions of US-Ca(OH)2 pretreatment and enzymatic hydrolysis were systematically optimized, and the suitable operating conditions were as follows: US power density of 0.65W/ml, US pretreatment time of 30min, Ca(OH)2 concentration of 0.75%, pretreatment temperature of 75°C, enzyme loading of 125FPU/g, and hydrolysis time of 72h. The reducing sugar yield of grass clipping pretreated by US-Ca(OH)2 reached 414mg/g, increasing by 3.5 times compared with that of raw grass clipping. The US-Ca(OH)2 pretreatment of grass clipping at low temperature significantly enhanced the potential of grass clipping as a promising raw material to produce biofuels.

Morphological, Chemical, and Thermal Characteristics of Nanofibrillated Cellulose Isolated Using Chemo-mechanical Methods

The objective of this research was to analyze the morphology, crystallinity, elemental components, and functional group changes, as well as thermal stability of nanofibrillated cellulose (NFC). Nanofibrillated cellulose has an irregular and aggregated shape with a diameter of about 100 nm. NFC self-aggregations were observed due to hydrogen bonding and Van-der Waals forces. The cellulose crystallinity index, atomic size, and polymorph of the NFC sample were found to be 63.57%, 2.2 nm, and cellulose I, respectively. The NFC sample was composed of various elemental components, such as C, O, N, Na, Al, Si, and K. IR analysis showed only small amounts of hemicellulose and lignin deposits, whereas cellulose functional groups appeared in several wavenumbers. Aromatic and oxygenated compounds, such as carboxylic acids, phenols, ketones, and aldehydes, were deposited as extractive on NFC; these compounds were associated with cellulose, hemicellulose, and lignin. The NFC thermal degradation process consisted of four steps: water evaporation (50-90 oC); hemicellulose degradation and glycosidic linkage cleavage (250-325 oC); amorphous cellulose and lignin degradation (325-429.29 oC); and cellulose crystalline degradation (above 429.29 oC).

Exploring crystalline structural variations of cellulose during pulp beating of tobacco stems

In this work, crystalline structural variations of cellulose during pulp beating of tobacco stems were characterized through X-ray diffraction (XRD) and FT-IR spectroscopy. The results showed that the correlation between the cellulose crystallinity index and the degree of beating was not a linear but an initially upward and then downward trend followed by a repeating fluctuation as a result of the beating action on amorphous regions first and then on crystalline cellulose. It was proposed that the whole beating process might be presumably divided into two phases in the case of the evolution of the crystallinity index. The crystallite sizes of 101 and 101¯ lattice planes showed an obvious fluctuation during the beating while the crystallite sizes and d-spacings from representative 002 lattice planes exhibited little change. Complementally, FT-IR characterization of cellulose structural properties further proved that the crystallinity index was highly affected by mechanical beating and the intact beating process might be divided into two stages characteristic of a first ascending and then descending tendency.

Chemical and Biological Pretreatments on Sugarcane Bagasse to Enhance its Enzymatic Hydrolysis.

AbstractAlkaline and biological lignocellulose pre‐treatments are commonly used to enhance enzymatic hydrolysis and improve ethanol production. In this study, 13C CPMAS NMR spectroscopy was used to describe changes in sugarcane bagasse (SCB) pre‐treated with NaOH, Ca(OH)2 and with Pycnoporus sanguineus. Changes in the contents of alkyl C, Carboxyl C, Aromatic C (tertiary, quaternary and p‐hydroxyphenyl C), O‐alkyl C, amino acids, ergosterol and chitin, as well as in the crystallinity index of cellulose were observed. Through a multivariate analysis, relations between changes in the chemical composition of SCB and enzymatic hydrolysis were established. P. sanguineus promotes better lignin decay, glucose release and hydrolysis yields than chemical pre‐treatments, and increases the amount of amino acids and ergosterol in SCB, while NaOH increases the cellulose crystallinity index. The hydrolysates were fermented with Saccharomyces cerevisiae for 96 h, and analysed through HPLC. The initial composition of the hydrolysates [mg.ml−1] and biomass production (cells.ml−1) were then related to the ethanol production and fermentation yields. We found that ethanol production and fermentation yields were negatively correlated with cell growth in Saccharomyces, but positively correlated with glucose consumption in the P. sanguineus pre‐treatment. We conclude that the biological pre‐treatment using P. sanguineus in the conditions hereby described, has a potential to increase ethanol productivity.

Conversion of various types of lignocellulosic biomass to fermentable sugars using kraft pulping and enzymatic hydrolysis

The aim of this work was to assess the utility of seven different kraft pulps produced from softwood (pine), hardwood (poplar, birch and beech), wheat straw and hemp (bast and harl) as potential sources of sugar feedstocks for fermentation processes. The pulps contained low amounts of hemicelluloses (1.9–8.2% d.w.) and lignin (1.7–15% d.w.). The crystallinity index values ranged from 55% (wheat straw pulp) to 79% (hemp bast pulp), while the average DP varied from around 230 (hemp bast pulp) to 1482 (poplar and birch pulps). The results of enzymatic hydrolysis showed that not only the residual lignin content but also the cellulose crystallinity index decided on the sugar yields while the average polymerization degree had a weak impact. More reducing sugars were obtained from the hardwood pulps and wheat straw pulp (100% d.w.) than from the pine pulp (around 89% d.w.) and two hemp pulps (40.5% d.w. and 44.7% d.w. from the bast and harl pulps, respectively). Glucose was the dominating (69–79% w/w) soluble sugar in enzymatic hydrolysates of the pulps. The sugar profiles of these hydrolysates make them suitable sugar feedstocks for fermentation processes.