Hemicellulosic Hydrolysate Research Articles

Inhibition kinetics of acetosyringone on xylanase in hydrolysis of hemicellulose.

Many phenolic compounds, derived from lignin during the pretreatment of lignocellulosic biomass, could obviously inhibit the activity of cellulolytic and hemicellulolytic enzymes. Acetosyringone (AS) is one of the phenolic compounds produced from lignin degradation. In this study, we investigated the inhibitory effects of AS on xylanase activity through kinetic experiments. The results showed that AS could obviously inhibit the activity of xylanase in a reversible and noncompetitive binding manner (up to 50% activity loss). Inhibitory kinetics and constants of xylanase on AS were conducted by the HCH-1model (β=0.0090±0.0009mM-1). Furthermore, intrinsic and 8-anilino-1-naphthalenesulfonic (ANS)-binding fluorescence results showed that the tertiary structure of AS-mediated xylanase was altered. These findings provide new insights into the role of AS in xylanase activity. Our results also suggest that AS was an inhibitor of xylanase and targeting AS was a potential strategy to increase xylose production.

A Review of Potential of Lignocellulosic Biomass for Bioethanol Production in Kenya

Lignocellulosic biomass is the earth’s most abundant and renewable resource, and, lignin is its strongest component. The lignocellulosic biomass has a potential to produce bioethanol for both domestic and industrial use. The presence of lignin in the biomass, however, hinders the processing and production of bioethanol from the biomass. Hence, to enhance the chances of bioethanol production from the lignocellulosic biomass, lignin has to be pre-treated. The pre-treatment process efficiently separates the interlinked complex components. During the pre-treatment process, the strong lignin component that is highly resistant and a major barrier to solubilization is broken down by hydrolysis of cellulose and hemicellulose. Pre-treatment of lignocellulosic biomass is therefore, necessary to make it more susceptible to microorganisms, enzymes, and pathogens. The initial pre-treatment approaches include physical, physicochemical, and biological methods. The major drawback of this pre-treatment process is its cost implications, as it’s very costly. Studies suggest that even though it’s a costly affair, the pre-treatment methods, however, have a significant impact on the efficient production of ethanol from biomass.
 Situation Analysis: Bioethanol production from lignocellulosic biomass has mostly been undertaken in Brazil, USA, China, and India. In Kenya, however, little research on bioethanol production from lignocellulosic biomass has been done and adopted. The present review paper seeks to outlay the benefits of bioethanol production from lignocellulosic biomass, the composition of lignocellulosic biomass, its properties, different pre-treatment methods alongside advantages, and, disadvantages, and challenges encountered during bioethanol production. This review eventually will be of great assistance to researchers while developing bioethanol from different lignocellulosic biomass. Research, technology adaption/adaptation, and policy targeted at growing bioethanol industry, could enable Kenya to grow her bioethanol industry.

New Proposal in a Biorefinery Context: Recovery of Acetic and Formic Acids by Adsorption on Hydrotalcites

Acetic acid (AA) and formic acid (FA) are two of the major fermentation inhibitors found in hemicellulosic hydrolysates. Their removal, which is necessary for the use of hydrolysates as fermentatio...

Co-production of ethanol-hydrogen by genetically engineered Escherichia coli in sustainable biorefineries for lignocellulosic ethanol production

This work shows the impact of the hydrogen and ethanol co-production –via dark fermentation– using a genetically engineered Escherichia coli in the environmental and economic sustainability of a lignocellulose-based biorefinery. Wheat straw (WS) and corn stover (CS) were used as feedstock. These were treated with either a 1.5% dilute sulphuric acid pretreatment (DAP) or an autohydrolysis followed by a 0.25% dilute sulphuric acid pretreatment (AH-VDAP) to compare the effect of the lignocellulosic matrix and its pretreatment as strategies for obtaining rich hemicellulosic hydrolysates, which were used as substrate in the dark fermentation experiments. The engineered E. coli strain used here increased 30% the co-production of hydrogen and ethanol compared to other genetically modified strains. Further, their impact on the profitability was determined on biorefinery conceptual designs incorporating the pretreatment and dark fermentation stages experimental results. The dark fermentation stage contributed with 20% to 30% of the total ethanol production in the lignocellulose-based biorefinery designs proposed here. Techno economic and sustainability analyses established that the biorefinery design using WS as feedstock and employing AH-VDAP presented the lowest negative environmental impact with the lowest Total Production Cost (TPC). This design produced 187,846 L EtOH/day with a TPC of $1.37 USD/L EtOH. The results showed that co-production schemes could be an alternative for lignocellulosic ethanol biorefineries.

Hydrolysis of Corncob Hemicellulose by Solid Acid Sulfated Zirconia and Its Evaluation in Xylitol Production

Corncob is an abundant agricultural residue containing high content of hemicellulose. In this paper, the hemicellulosic hydrolysate was prepared from the hydrolysis of corncob using the solid acid sulfated zirconia as a catalyst. According to response surface analysis experiments, the optimum conditions for preparing hemicellulosic hydrolysate catalyzed by sulfated zirconia were determined as follows: solid (sulfated zirconia)-solid (corncob) ratio was 0.33, solid (corncob)-liquid (water) ratio was 0.09, temperature was 153 °C, and time was 5.3 h. Under the optimized conditions, the soluble sugar concentration was 30.12 g/L with a yield of 033 g/g corncob. Subsequently, xylitol production from the resulting hemicellulosic hydrolysate was demonstrated by Candida tropicalis, and results showed that the yield of xylitol from the hemicellulosic hydrolysate could be significantly improved on a basis of decolorization and detoxification before fermentation. The maximum yield of xylitol from the hemicellulosic hydrolysate fermented by C. tropicalis was 0.76 g/g. This study provides a new attempt for xylitol production from the hemicellulosic hydrolysate.

Synergic recombinant enzyme association to optimize xylo-oligosaccharides production from agricultural waste

Abstract Xylo-oligosaccharides (XOS) are one of the classes of prebiotics obtained from lignocellulosic biomass, by hydrolysis of hemicellulose, abundant in agroindustrial residues. Several endoxylanases were studied in order to provide better conversion of the biomass to XOS. The resulting product presents multi-benefits, favoring the intestinal microbiota and maintaining the viability of probiotics in food. XOS production from sugarcane straw by action of thermostable recombinant endoxylanase of Cryptococcus flavescens, expressed in Pichia pastoris GS115 using vector pGAPZαA, in synergic association with α- l -arabinofuranosidase (GH 51) (Megazyme®) was optimized using a central composite rotatable design (CCRD), enabling 72.56% of xylan conversion. The main products xylobiose and xylotriose are short chain oligosaccharides preferred by probiotics. Hydrolysis of xylan from sugarcane straw using endoxylanase and α- l -arabinofuranosidase has great potential for XOS production with high prebiotic activity, representing a possible sustainable way to reduce enzymatic and raw material costs.

Multi-scale study of the integrated use of the carbohydrate fractions of sugarcane bagasse for ethanol and xylitol production

A multi-scale study of sugarcane bagasse (SB) pretreatments and integrated developments for use of its carbohydrates portions for ethanol and xylitol production, are presented. In a first approach, after SB acid hydrolysis, hemicellulosic ethanol production was investigated, verifying ethanol yield of 0.31 g/g and volumetric productivity (QP) of 0.1 g/L.h. Xylitol production was also studied, showing xylitol yield and QP of 0.61 g/g and 0.38 g/L.h, respectively. Thus, remaining cellulignin from acid pretreatment was submitted to alkaline hydrolysis followed by Semi-Simultaneous Saccharification and Co-fermentation in sequential processes to ethanol production, by using mixture of SB hemicellulosic and enzymatic hydrolysate as carbon source, verifying QP of 0.6 g/L.h. Moreover, a biomass multi-scale study was conducted by analysis of MEV, X-Ray, FTIR and Ramman Spectroscopy, verifying clear changes in SB structure along each pretreatment. These novel approaches indicated the potential of these integrated use of SB carbohydrates portion for bioproducts obtaining from SB in sustainable processes.

Enabling butanol production from crude sugarcane bagasse hemicellulose hydrolysate by batch-feeding it into molasses fermentation

Butanol is a chemical and advanced biofuel whose fermentative production from hemicellulose hydrolysates is hindered by lignocellulose-derived microbial inhibitory compounds. In this work, Clostridium saccharoperbutylacetonicum DSM 14923 was not able to ferment a sugarcane hemicellulose hydrolysate supplemented with either laboratory-grade nutrients or sugarcane molasses. To circumvent this problem, the crude hemicellulose hydrolysate was fed, after 24 h, to a molasses fermentation containing 45 g/L total reducing sugars. Without the need of supplementing nutrients, the culture was able to co-ferment sucrose, glucose, fructose, and xylose (conversion of sucrose and xylose were 81 and 90 %, respectively) in a fermentation containing a diluted molasses-to-hydrolysate volume ratio of 3:1. Butanol yield (0.31 g/g) was remarkable, and butanol titer was 10.0 g/L after 72 h of fermentation. Therefore, this research demonstrated that sugarcane molasses ‒ a by-product of the sugar industry rich in sucrose and nutrients ‒ can be an efficient feedstock for enabling the production of butanol from sugarcane bagasse hemicellulose hydrolysate.

A two-step process for pre-hydrolysis of hemicellulose in pulp-impregnated effluent with high alkali concentration to improve xylose production

The viscose fiber production process is accompanied by the accumulation of pulp-impregnated effluent (PIE), including hemicellulose and large amounts of alkali, and discharge of PIE will cause environment pollution. This paper aims to relieve the inhibition of high concentration of alkali on xylose production from hydrolysis of hemicellulose in PIE. Based on the fact that solid acid uses H+ at the acid sites to exchange with cations in PIE and can be recycled, a two-step method including an extra pretreatment process before pre-hydrolysis (SPP) is proposed. After the alkali was removed by the H+ dissociated from solid acid in the extra pretreatment process, the pH of PIE dropped from 14 to 4, and the content of Na+ and proteins was reduced by 99.13 % and 78.51 %, respectively. After SPP, the polymerization degree of the hemicellulose decreased by 73.4 %, and the subsequent enzymatic hydrolysis process was promoted. Finally, the xylose yield of SPP followed by enzymatic hydrolysis reached 57.15 g/L, which was 145.38 % more than that of enzymatic hydrolysis alone. The load of a downstream ion purification procedure was relieved compared to that of inorganic acid hydrolysis. The development of SPP contributes to the resource utilization of high alkali concentration wastewater.

Assessment of different Bacillus coagulans strains for l-lactic acid production from defined media and gardening hydrolysates: Effect of lignocellulosic inhibitors

Cellulose valorisation has been successfully addressed for years. However, the use of hemicellulosic hydrolysates is limited due to the presence of C5-sugars and inhibitors formed during pretreatment. Bacillus coagulans is one of the few bacteria able to utilize both C6- and C5-sugars to produce l-lactic acid, but its susceptibility to the lignocellulosic inhibitors needs further investigation. For such a purpose, the tolerance of different B. coagulans strains to increasing concentrations of inhibitors is studied. The isolated A162 strain reached the highest l-lactic acid productivity in all cases (up to 2.4 g L−1 h−1), even in presence of 5 g L−1 of furans and phenols. Remarkably, most of furans and phenolic aldehydes were removed from defined media and hemicellulosic gardening hydrolysate after fermentation with A162. Considering the high productivities and the biodetoxifying effect attained, A162 could be pointed out as a great candidate for valorisation of mixed sugars from hemicellulosic hydrolysates with high inhibitors concentration, promoting the implementation of lignocellulosic biorefineries.

Multifarious pretreatment strategies for the lignocellulosic substrates for the generation of renewable and sustainable biofuels: A review

Currently major part of the world’s energy requirements is fulfilled by fossil resources. Severe economic and environmental problems along with their limited resources are still a major issue. Long-term environmental and commercial concern has focussed into huge research in the past decades to replace fossil fuels with renewable sources of energy. The main focus of energy research is lignocellulosic substrates, which seems to be the best for energy application due to easily availability, cost-effective and environment favourable production process. Therefore, lignocellulosic materials provide economical, environmental and energetic benefits with an alternative to traditional or high cost substrates. However, the close association of major constituents of lignocellulosic biomass forms different barriers, which hinders the enzymatic hydrolysis of cellulose and hemicellulose to different fermentable sugars. To overcome this problem, different pretreatment approaches including physical, chemical, biological and combination of them have been used to improve the enzymatic accessibility or digestibility of lignocellulosic biomass. Various pretreatment methods have specific effect on different lignocellulosic components. Among all the methods, biological methods have performed better with respect to yield, cost and environmental related problems. Pretreated substrates from various pretreatments have been saccharified for the production of sustainable and renewable biofuels like ethanol, butanol, hydrogen, acetoin and 2,3-butanediol. • Multifarious pretreatment strategies for the lignocellulosic substrates. • Biological pretreatment of lignocellulosic biomass and analysis. • Production of renewable and sustainable biofuels from lignocellulosic substrates. • Techno-economical analysis of various pretreatment methods.

Physiochemical properties and pyrolysis behavior evaluations of hydrochar from co-hydrothermal treatment of rice straw and sewage sludge

Co-hydrothermal treatment is an effective approach to recovery the energy and fuels from organic matter in rice straw (RS) and sewage sludge (SS). In this study, the basic fuel characteristics, ash composition, the subsequent pyrolysis behavior and relevant reaction kinetic parameters of obtained hydrochar were evaluated. The results indicated that co-hydrothermal treatment improved the fuel characteristics of hydrochar with high HHV and low N and S contents. FTIR analysis indicated that the presence of the synergy between RS and SS during co-hydrothermal treatment that the organic acids from hydrolysis of hemicellulose promoted the degradation of N-containing functional groups. In addition, the ash composition analyses showed that the obtained hydrochar had high ash fusion temperature as a result of the high removal efficiency of alkali metals during co-hydrothermal treatment. Moreover, co-hydrothermal treatment can promote the pyrolysis reaction by reducing the activation energy with the synthetic effect of RS and SS during co-hydrothermal treatment process. In summary, co-hydrothermal treatment improved the physiochemical properties and promoted the pyrolysis behavior of obtained hydrochar from RS and SS.

Investigation of factors that inhibit furfural production using metal chloride catalysts

To increase the furfural yield from corncobs biomass when implementing metal chloride-based catalysts, four different routes that could inhibit furfural production were investigated: hydrolysis of hemicellulose, oxidation of corncobs and xylose, and humins formation. The evaluation was performed at both 90 and 170 °C. The results show that the hydrolysis of hemicellulose is not a factor for inhibiting furfural production at 170 °C while humins formation is. Oxidation of corncobs and xylose are factors for inhibiting furfural production at 90 and 170 °C. A novel method for predicting the activity of a catalyst for furfural production based on the fundamental chemical properties of metal ions (e.g., Lewis acid strengths, oxidizing properties, and solubility products of the corresponding hydroxides) was developed. The proposed method explains why AlCl3 enables the highest furfural production yield among FeCl3, FeCl2, AlCl3, and CuCl2.

Hydrothermal liquefaction of wood using a modified multistage shrinking-core model

Wood liquefaction in hot compressed water is modeled using the hydrolysis of Cellulose, Hemicellulose, and Lignin. These three components are reacted under catalyst-free subcritical conditions in a temperature range from 553 K to 640 K, and the heating rate ranges from 2 K/min to 6 K/min. Using a simplified reaction scheme, water-soluble products11WSP: - Water soluble products (WSP), Biocrude, char, and gas are generated through intermediates with each wood component. A modified multistage shrinking core model is employed to simulate biomass particle degradation. The reaction and kinetic regime of the hydrothermal liquefaction22HTL: -Hydrothermal Liquefaction (HTL) process are treated separately for each wood component. Although the lack of initial fast reaction kinetic data limits the development of more accurate models, computed results displayed a generous fit to data from the literature. At 593 K for a 2 K/min heating rate and particle size of 0.08 mm, biocrude shows the maximum yield of 26.87% for wood liquefaction. Although lower heating rates show fast initial lignin hydrolysis, for longer residence times, and close to the critical point, yield outputs show similar yields. Meanwhile, char and gas yields of cellulose model show maximums of 55 wt% and 25 wt% respectively at 640 K with a 2 K/min heating rate. Nevertheless, char yield values become very similar at 640 K for different heating rates for the cellulose hydrolysis model. Both cellulose and lignin hydrolysis models show better hydrolysis with smaller particle sizes. Besides, lignin decomposition shows more dependence on the particle size, where it decomposes much faster with 0.08 mm particle and slower than Cellulose with the 1 mm particle.

Model-based optimization of xylooligosaccharides production by hydrothermal pretreatment of Eucalyptus by-product

Eucalyptus wood is the main source of fiber for the production of paper and cellulose in South America. One of the by-products of the pulp industry is sawdust generated during wood chip production; sawdust from Eucalyptus is denominated as Eucalyptus by-product (EB). Xylooligosaccharides (XOS) are oligomers mainly comprising xylose units, which have beneficial effects on health. In this study, was report the optimization of XOS production through the hydrothermal pretreatment (HP) of EB. A central composite experimental design comprising a 23-factorial design with six axial points and four replicates at the central point was employed to optimize the HP conditions for maximum XOS production using response surface method; these conditions were as follows: temperature of 161 °C, reaction time of 65 min, and consistency of 10 %. The hemicellulosic hydrolysate showed potential for the production of XOS, containing 60 milligrams of XOS per gram of EB.

Effect of the autohydrolytic treatment of Miscanthus sacchariflorus Andersson on the yield of the reducing substances during the subsequent fermentolysis

The effect of the autohydrolytic treatment of Miscanthus sacchariflorus Andersson on the yield of the reducing substances during the subsequent fermentolysis has been determined. It was established that a change in the conditions of the auto-hydrolytic treatment of Miscanthus sacchariflorus Andersson induces a formation of solid fractions containing cellulose, lignin, hemicellulose and mineral substances, the ratio of which depends on the severity factor, i.e. temperature and processing time. It was shown that at the severity factor of 5.67, almost complete hydrolysis of hemicellulose occurs, however, there is an increase in the lignin content in the solid fraction (up to 46.0 %) relative to the lignin content in the feedstock (20.8 %), which is due to lignin condensation with a consequent formation of pseudo lignin. The highest content of cellulose in the solid phase is observed as a result of hydrolytic processing of raw materials with a severity factor of 4.17 to 4.39, a temperature of 160 о С and a processing time of 25 min. At an increased temperature, an increase in the acidity of the medium catalyzes the hydrolysis of cellulose and reduces its content in the solid fraction to 60 % at a severity factor of 5.67. During the auto-hydrolytic treatment of Miscanthus sacchariflorus Andersson, an increase in the ash content in the solid fraction is observed. The solid fractions obtained after treatment with Miscanthus sacchariflorus Andersson were used as a substrate and were subjected to enzymatic hydrolysis with the enzyme preparations “Cellolux-A” and “BrewZime BGX” at an initial substrate concentration of 33 g/l. The increase in the yield of reducing substances has shown a steady increase with the removal of hemicelluloses and reached its maximum value (45.1 %) with an increase in the treatment severity factor to 4.48. The availability of the cellulose surface for the action of enzymes has decreased with an increase in the stiffness factor beyond a value of 4.48 due to the accumulation of lignin in the solid phase, as evidenced by a decrease in the yield of reducing substances in the enzyme to 31.8 %.

Valorization of apple pomace using bio-based technology for the production of xylitol and 2G ethanol.

Apple pomace was studied as a raw material for the production of xylitol and 2G ethanol, since this agroindustrial residue has a high concentration of carbohydrate macromolecules, but is still poorly studied for the production of fermentation bioproducts, such as polyols. The dry biomass was subjected to dilute-acid hydrolysis with H2SO4 to obtain the hemicellulosic hydrolysate, which was concentrated, detoxified and fermented. The hydrolyzate after characterization was submitted to submerged fermentations, which were carried out in Erlenmeyer flasks using, separately, the yeasts Candida guilliermondii and Kluyveromyces marxianus. High cellulose (32.62%) and hemicellulose (23.60%) contents were found in this biomass, and the chemical hydrolysis yielded appreciable quantities of fermentable sugars, especially xylose. Both yeasts were able to metabolize xylose, but Candida guilliermondii produced only xylitol (9.35gL-1 in 96h), while K. marxianus produced ethanol as the main product (10.47gL-1 in 24h) and xylitol as byproduct (9.10gL-1 xylitol in 96h). Maximum activities of xylose reductase and xylitol dehydrogenase were verified after 24h of fermentation with C. guilliermondii (0.23 and 0.53U/mgprot, respectively) and with K. marxianus (0.08 e 0.08U/mgprot, respectively). Apple pomace has shown potential as a raw material for the fermentation process, and the development of a biotechnological platform for the integrated use of both the hemicellulosic and cellulosic fraction could add value to this residue and the apple production chain.

Green and novel adsorbent from rice straw extracted cellulose for efficient adsorption of Hg (II) ions in an aqueous medium

Cellulose nanofibrils (CNF) were extracted from rice straw, a waste lignocellulosic biomass, using soda cooking, which resulted in a reduction of the recalcitrance of biomass, leading to hydrolysis of hemicellulose into sugars, which was subsequently washed, leaving a residue of cellulose. FTIR confirmed the removal of lignin and hemicellulose to yield pure CNF while XRD, DTG and TGA results showed increased crystallinity and thus higher thermal stability.CNFs were functionalized using l-methionine, a natural amino acid, to graft sulfides and amino functional groups onto the surface of fibers. Structural and morphological changes induced by grafting were confirmed by FTIR, XRD, TEM, Mapping and Elemental analysis. Modified fibers exhibited a high adsorption capacity of 131.86 mg/g for Hg (II) ions even at low concentration i.e. 300 ppm owing to sulfides. Optimization of pH on adsorption behavior was established through extensive pH studies and adsorption kinetics. Adsorption follows pseudo second order kinetic model indicating chemisorption for removal of Hg (II) ions from simulated wastewater.

One-step process to produce furfural from sugarcane bagasse over niobium-based solid acid catalysts in a water medium

This study investigated the production of furfural from sugarcane bagasse over niobic acid (Nb2O2·nH2O, called as NbO) or niobium phosphate (NbOPO4·nH2O, called as NbP) in a one-step process performed in water. The variables temperature (T), the mass of catalyst (mcat), reaction time (rt), and vibration time (Vt) for mixing SCB and catalyst were studied through a design of experiments. After 5 h at 150 °C, the furfural yields were 52.1 g kg−1 for NbO and 59.3 g kg−1 for NbP, while the yields of xylose and arabinose were, respectively, 69.7 g kg−1 and 6.4 g kg−1 for NbO and 147.4 g kg−1 and 11.1 g kg−1 when using NbP. It was proved that furfural yield is independent of the SCB genotype. The selective depolymerization and hydrolysis of hemicellulose into monomers and its further dehydration to furfural were observed. The cellulose and lignin remained readily utilizable for further processing. The better catalytic performance of NbP was attributed to the higher ratio of Brønsted to Lewis acid sites on its surface than NbO.

Acid-functionalized magnetic nanocatalysts mediated pretreatment of sugarcane straw: an eco-friendly and cost-effective approach

The ubiquitous nature of lignocellulosic biomass on planet earth and its economic viability attracted a great deal of attention from researchers and becomes foremost feedstock for biofuel production particularly bioethanol. However, due to complexity in structure, its pretreatment is essentially required prior to actual use. In the present study, a promising approach has been proposed through the development of acid-functionalized magnetic nanocatalysts. Two different acid-functionalized magnetic nanocatalysts i.e. alkylsulfonic acid functionalized magnetic nanoparticles (Fe3O4-MNPs-Si-AS) and butylcarboxylic acid functionalized magnetic nanoparticles (Fe3O4-MNPs-Si-BCOOH) were developed and their efficacy was studied in the pretreatment of sugarcane straw at varying concentrations (100, 200, 300, 400, 500 mg/g of straw). The enhanced concentration dependent production of sugar (xylose) was reported in case of both the nanocatalysts. The maximum 17.06 g/L for Fe3O4-MNPs-Si-AS and 15.40 g/L for Fe3O4-MNPs-Si-BCOOH sugar was reported at 500 mg which is comparatively higher than normal acid (H2SO4) (14.63 g/L) and non-treated (0.24 g/L) sugarcane straw. Further, both the nanocatalysts were recovered by applying an external magnetic field and reused for the next two subsequent cycles of pretreatment. It was observed that with every reuse of nanocatalysts the concentration of sugar production was reduced. Moreover, generation of very less amount of toxic inhibitors was reported in the hemicellulosic hydrolyzate obtained in the present study. Considering these facts, it is believed that such nanocatalysts can be used as an effective, eco-friendly and economically viable alternative to the conventional pretreatment agents like mineral acids.