Search

The removal of lignin is important to the recovery of saccharides from the pre-hydrolysis liquor (PHL) in kraft-based dissolved pulp production. A one-step process for lignin removal from PHL via treatment with horseradish peroxidase (HRP) in the presence of Ca 2+ was proposed, and its principle was studied. The results demonstrated synergy between HRP and Ca 2+ in lignin removal from PHL, whereas NH 4 + had little effect on lignin removal. HRP treatment in the presence of 60 mmol/L of Ca 2+ resulted in a lignin removal of 64.8% accompanied by a saccharide loss of 14.2%. HRP catalyzed both the polymerization and depolymerization of the lignin in the PHL. The HRP-catalyzed lignin polymerization rendered some lignin insoluble enabling it to be directly removed. The HRP-catalyzed depolymerization of lignin decreased its molecular weight with an evident increase in its carboxyl content. The insoluble complexes formed between the lignin with carboxyl and the Ca 2+ facilitated the removal of the depolymerized lignin., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Pseudo-lignin induced by high-severity dilute acid treatment of lignocellulose has been widely studied because of its detrimental effect on enzymatic hydrolysis. However, cooling-induced pseudo-lignin (CIPL) formed during the cooling process after treatment has always been ignored and never been characterized systematically. To investigate the formation and chemistry of CIPL, liquid hot water treatments of poplar wood were conducted. Samples of treated wood and hydrolysate were taken out from digester at various temperatures during the cooling process for characterization. SEM images evidenced a progressive deposition of CIPL on the surface of the treated wood during cooling process with a yield of 19.6 mg/g treated wood. However, the treated wood which was collected isothermally at reaction temperature showed no pseudo-lignin. Variation of organic compounds in hydrolysate from lignocellulose degradation during cooling process revealed that depolymerized lignin and furfural accounted for 80.4 and 10.6 % of CIPL, respectively, while soluble saccharides from carbohydrate hydrolysis were independent from CIPL formation. These findings stress the importance of isothermal separation of treated wood and hydrolysate. Otherwise, CIPL should hinder enzymatic hydrolysis for biofuels production or delignification for cellulosic fiber production. [ABSTRACT FROM AUTHOR]

The removal of colloidal particle and lignin from a pre-hydrolysis liquor (PHL) of biomass is essential for its processing as well as for the value-added utilization of saccharides in the PHL. In this paper, pectinase was used to treat an aspen PHL obtained by pre-hydrolysis at 160 °C, and a novel process in which pectinase treatment was followed by cationic polymer flocculation to enhance colloidal particle and lignin removal was investigated. The results showed that pectinase treatment caused an approximately 50% decrease in the cationic demand of the aspen PHL. For the controlled PHL, approximately 68 mg/L poly-dimethyl diallyl ammonium chloride (pDADMAC) was needed to remove nearly all of the colloidal particles with 40.3% maximum lignin removal; for the enzyme-treated PHL, only approximately 34 mg/L pDADMAC was needed to remove nearly all of the colloidal particles with 43.3% lignin removal. In addition, the enzyme treatment decreased the loss of saccharides during subsequent pDADMAC treatment at the concentration necessary for maximum lignin removal. [ABSTRACT FROM AUTHOR]

In this study, the pre-hydrolysis liquor (PHL) was recycled during aspen chip water pre-hydrolysis, and the effects of PHL recycling on the extraction and accumulation of the hemicellulosic saccharides especially that with high molecular weight in the PHL were studied. The results showed that the concentration of hemicellulose saccharides in PHL depended on the pre-hydrolysis temperature and PHL recycling times. Compared to the unrecycled PHL, the concentration of hemicellulosic saccharides in PHL increased significantly when recycling PHL once or twice at 170 °C. Furthermore, the amount of high-molecular-weight hemicelluloses (HMHs) in PHL recycled once at 170 °C increased from 2.58 g/L (unrecycled) to 6.18 g/L, but the corresponding average molecular weight of HMHs decreased from 9.2 kDa to 7.6 kDa. The concentration of hemicellulosic saccharides in PHL decreased with PHL recycling time at 180 °C, accompanied by the formation of a significant amount of furfural. [ABSTRACT FROM AUTHOR]

[Display omitted] • Poplar was pretreated by reusable organic solvent under mild temperature (≤100 °C). • Almost all hemicelluloses and part of lignin was extracted with cellulose retained. • Sulfonic acid groups were introduced into lignin structure remained in substrates. • 89% improved glucose conversion compared with that of non-sulfonated substance. • New strategy is exploited to realize sulfonation and promote biomass bioconversion. Biomass pretreatment is an essential strategy to overcome biomass recalcitrance and promote lignocellulosic bioconversion. Here, a reusable organic solvent system (formic acid-methanesulfonic acid) was explored to pretreat poplar under a mild temperature (below 100 °C). The results showed that the co-solvent system could extract basically complete hemicelluloses and part of lignin with original cellulose retained in the pretreated substrates. Meanwhile, sulfonic acid groups were introduced into lignin structure remained in the substrates. The glucose conversion yield of the substrates with a higher concentration of sulfonic acid groups (13.2 mmol/kg) reached 45.9 % by reducing the hydrophobic interaction between lignin and cellulase, showing 89.3 % improvement compared with that of the substrates treated with single formic acid. This progressive study aimed to develop a new strategy to realize sulfonation and promote enzymatic hydrolysis of substrates by using mild organic solvent pretreatment. [ABSTRACT FROM AUTHOR]

Prehydrolysis of lignocellulose produces abundant hemicellulose-derived saccharides (HDS). To obtain pure HDS for application in food or pharmaceutical industries, the prehydrolysis liquor (PHL) must be refined to remove non-saccharide compounds (NSC) derived from lignin depolymerization and carbohydrate degradation. In this work, activated carbon (AC) adsorption was employed to purify HDS from NSC with emphasis on adsorption selectivity. The adsorption isotherms showed the priority of NSC to be absorbed over HDS at low AC level. However, increase of AC over 90% of NSC removal made adsorption non-selective due to competitive adsorption between NSC and HDS. Size exclusion chromatography showed that the adsorption of oligomeric HDS was dominant while monomeric HDS was inappreciable. The limited selectivity suggested that AC adsorption is infeasibility for HDS purification, but applicable as a pretreatment method. [ABSTRACT FROM AUTHOR]

A combined process of lime treatment and mixed bed ion exchange was proposed to separate hemicellulose-derived saccharides (HDS) from prehydrolysis liquor (PHL) of lignocellulose as value added products. The optimization of lime treatment achieved up to 44.2% removal of non-saccharide organic compounds (NSOC), mainly colloidal substances, with negligible HDS degradation at 0.5% lime level and subsequent neutralization by phosphoric acid. The residual NSOC and calcium ions in lime-treated PHL were eliminated by mixed bed ion exchange. The breakthrough curves of HDS and NSOC showed selective retention toward NSOC, leading to 75% HDS recovery with 95% purity at 17 bed volumes of exchange capacity. In addition, macroporous resin showed higher exchange capacity than gel resin as indicated by the triple processing volume. The remarkable selectivity of the combined process suggested the feasibility for HDS separation from PHL. [ABSTRACT FROM AUTHOR]

Prehydrolysis of wood biomass prior to kraft cooking provides a stream containing hemicellulose-derived saccharides (HDSs) but also undesired non-saccharide compounds (NSCs) that were resulted from lignin depolymerization and carbohydrate degradation. In this study, a combined process consisting of lime treatment, resin adsorption, and gel filtration was developed to separate HDSs from NSCs. The macro-lignin impurities that accounted for 32.2% of NSCs were removed by lime treatment at 1.2% dosage with negligible HDSs loss. The majority of NSCs, lignin-derived phenolics, were eliminated by mixed bed ion exchange resin, elevating NSCs removal to 94.0%. The remaining NSCs, furfural and hydroxymethylfurfural, were excluded from HDSs by gel filtration. Chemical composition analysis showed that xylooligosaccharides (XOS) with the degree of depolymerization from 2 to 6 accounted for 28% of the total purified HDSs. [ABSTRACT FROM AUTHOR]

Saccharides and lignin components in prehydrolysis liquor (PHL) from kraft-based dissolving pulp production was characterized after being fractionated using membrane filtration. The results showed that the membrane filtration provided a method for organics fractionation with considerable recovery rate, but exhibited some disadvantages. Besides the limited ability in purifying oligosaccharides (OS) due to the overlaps of molecular weight distribution with lignin components, the membrane filtration could not improve the homogeneity of OS as indicated by the analysis of chemical compositions and the degree of polymerization (DP), which may be ascribed to the linear conformation of OS. The characterization of lignin components indicated a great potential for polymer industry because of the remarkable content of phenolic hydroxyl groups (PhOH), especially for low molecular weight (LMW) fraction. It was concluded the organics in PHL provided streams of value-added chemicals. However, the practical significance thereof can be realized and maximized only when they are successfully and completely fractionated. [ABSTRACT FROM AUTHOR]

The specific elimination of lignin derivatives from wood hydrolysate without sugar loss has great practical significance to biorefinery and bioenergy. In the present study, a process consisting of calcium hydroxide and anion exchange resin treatments was developed for the purpose of selective removal of lignin from wood prehydrolysis liquor (PHL). Particular emphasis was made on the ionization of phenolic lignin, and the subsequent binding to metallic salts. It was observed that phenolic hydroxyl groups (PhOH) in lignin played an important role in lignin removal. The results showed that up to 95.2% lignin was removed from PHL with 78.8% sugar recovery. This suggested that the proposed process is highly specific to lignin, and therefore can be envisaged as a great contribution to wood-sugar production or bioenergy conversion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pre-hydrolysis is considered as a promising technology in the biorefinery process. • "Pseudo-lignin" were formed and deposited on biomass surface during pre-hydrolysis. • The surface-deposits could be removed efficiently by isothermal phase separation. • More sugars were extracted by interrupting the formation of "pseudo-lignin". • The efficient removal of surface-deposits improved subsequent enzymatic hydrolysis. During the traditional autohydrolysis, formation and deposition of "pseudo-lignin" and lignin droplets on the surface of biomass had a detrimental effect on the subsequent biomass conversion. In this study, isothermal phase separation was introduced into autohydrolysis, and the effects of isothermal phase separation on the dissolution of components and enzymatic hydrolysis of bamboo were studied. The research showed that isothermal phase separation after autohydrolysis without cooling had an effective reduction in the deposition of "pseudo-lignin" and lignin droplets on the residues surface. After isothermal phase separation, the contents of sugar (14.05 g/L) and lignin (6.16 g/L) in pre-hydrolysates increased by 20% and 19% compared with control, respectively. Moreover, the efficient removal of "pseudo-lignin" and lignin droplets from cell wall surface could further promote the biological conversion of pretreated biomass (22% higher than that of control) during the subsequent enzymatic hydrolysis. [ABSTRACT FROM AUTHOR]