Lignin fractionation to realize the comprehensive elucidation of structure-inhibition relationship of lignins in enzymatic hydrolysis.

A better understanding of the relationship between lignin structures and their inhibitory effects in enzymatic saccharification would facilitate the development of lignocellulose biorefinery process. However, the heterogeneity of lignins challenges the elucidation of lignin structure-inhibition correlation. In this study, two types of lignin fractions including ethanol soluble lignins and ethanol insoluble lignins were respectively isolated from the poplars pretreated with various severities. The impacts of pretreatment severities on the structural changes of lignin fractions were studied from the perspective of inter-units linkages, condensed aromatic substructure, and hydroxyl groups. Furthermore, it was observed that lignin addition strongly inhibited the enzymatic saccharification of pure cellulose by 13.3 âˆ¼ 56.3%. Lignin inhibition extents were increased with the elevated pretreatment severity. The relationships between the lignin structural features and lignin inhibition were analyzed, which revealed that the contents of condensed aromatic units and phenolic hydroxyl were crucial factors determining the lignin inhibition.

In-situ lignin modification with polyethylene glycol-epoxides to boost enzymatic hydrolysis of combined-pretreated masson pine.

Acid pretreatment was insufficient to disrupt the recalcitrance derived from lignins in softwood, thus a lignin-targeting post-treatment was required. In this study, a combined acid and alkali pretreatment with polyethylene glycol-epoxides (PEG-epoxides) was developed on masson pine. Results showed although the combined pretreatment achieved a limited delignification, but a remarkably increment of 15.9-34.9% on hydrolysis yields was achieved. This was ascribed to the successful incorporation of hydrophilic PEG chains to residual lignins. Moreover, the improvement on enzymatic digestibility varied with the PEG chain lengths in modifiers. The underlying reasons for this improvement were primarily investigated by monitoring the lignin properties as well as water retention values variation after in-situ lignin modification by PEG-epoxides with varied molecular weights. It indicated that the enzymatic hydrolysis improvement was mainly due to both reduced enzyme nonspecific adsorption and increased fiber swelling. Results will give new insights to resolve the challenge on softwood biorefinery.

Synergistic effects of hydrothermal and deep eutectic solvent pretreatment on co-production of xylo-oligosaccharides and enzymatic hydrolysis of poplar.

Full utilization of lignocellulose is critical for its biorefinery development. In this study, a sustainable biorefinery process based upon poplar sawdust was established using sequential hydrothermal and deep eutectic solvent treatment (HP-DES). Results showed that single hydrothermal pretreatment (HP) could produce 53.2% xylo-oligosaccharides (XOS) (based on raw xylan), while the enzymatic digestibility was low. Conversely, single DES treatment achieved effective enzymatic digestibility but low XOS yields. As compared to HP, both DES treatment and HP-DES showed high selectivity for lignin removal and high glucose yield. Surprisingly, most of HP-DES residues had obviously lower enzymatic digestibilities than those of single DES residues. This was mainly explained by the differences of the surface lignin contents between DES and HP-DES residues. Moreover, nearly complete enzymatic hydrolysis of HP-DES residues was achieved with the addition of bovine serum albumin. This work demonstrated this HP-DES yielded XOS, fermentable sugar, and pure lignin with high processibility.

Comparative study on enzymatic digestibility of acid-pretreated poplar and larch based on a comprehensive analysis of the lignin-derived recalcitrance.

Enzymatic digestibility of an acid-pretreated poplar (AP, 42.9%) was superior to that of a similarly acid-pretreated larch (AL, 12.5%). Effects of lignin-related recalcitrance on enzymatic hydrolysis were comprehensively investigated by disrupting the two predominant lignin fractions present in acid-pretreated material (extractable lignin and bulk lignin). Lignin removal and bovine serum albumin (BSA) addition were performed to estimate the relative contributions of lignin towards physical blocking and enzyme binding on enzymatic hydrolysis. The lignin physical blocking played a more significant role in limiting the enzymatic hydrolysis of AL. BSA addition improved enzymatic hydrolysis of AP more significantly than AL. Moreover, the effects of lignin embedded in the lignocellulosic matrix on enzyme non-productive binding were compared with the isolated lignin. It indicated that the lignin distribution would influence the lignin effects on enzyme non-productive binding during enzymatic hydrolysis. Results will give insights towards improvement of enzymatic hydrolysis on acid-pretreated woody biomass.

Promoting enzymatic saccharification of organosolv-pretreated poplar sawdust by saponin-rich tea seed waste.

Organosolv pretreatment with two ethanol concentrations (25% and 50%, v/v) was performed to improve enzymatic saccharification of poplar sawdust. It was found that lower ethanol concentration (25%, v/v) pretreatment resulted in a higher enzymatic digestibility of poplar (38.1%) due to its higher xylan removal and similar lignin removal ratios, compared to that pretreated with 50% (v/v) ethanol pretreatment (27.5%). However, the residual lignin still exhibited a strong inhibition on enzymatic hydrolysis of organosolv-pretreated poplar (OP). Bio-surfactant preparations including tea saponin (TS), TS crude extract, and tea seed waste were applied in enzymatic hydrolysis of OP, due to their potential ability of reducing enzyme non-productive binding on lignin. Their optimal loadings in enzymatic hydrolysis of OP were optimized, which indicated that adding 0.075 g/g glucan of TS improved the 72-h glucose yield of OP by 48.3%. Moreover, adding TS crude extract and tea seed waste exhibited the better performance than TS for improving enzymatic hydrolysis of OP. It was verified that the presence of protein in TS crude extract and tea seed waste accounted for the higher improvement. More importantly, the directly application of tea seed waste in enzymatic hydrolysis could achieve the similar improvement on enzymatic hydrolysis of OP, where chemosynthetic surfactant (PEG6000) was added. The residual enzyme activities in supernatant of enzymatic hydrolysis were also determined to reveal the changes on enzyme adsorption after adding surfactants. Generally, tea seed waste could be directly applied as an alternative to chemosynthetic surfactants to promote enzymatic hydrolysis of lignocelluloses.

Facilitating enzymatic digestibility of larch by in-situ lignin modification during combined acid and alkali pretreatment.

To overcome the recalcitrance of residual lignins in acid-pretreated larch (AL), a combined acid and alkali pretreatment with in-situ lignin modification was developed in this study. The results showed that introducing in-situ lignin modification with 2-naphthol to acid pretreatment (160 and 180 oC) improved the enzymatic digestibility of AL by 12.7-14.4%, through suppressing lignin repolymerization. The obviously higher improvement (57.8-88.3%) was achieved by applying alkali post-treatment (90 oC) with poly (ethylene glycol) diglycidyl ether (PEGDE) on AL, mainly due to the function of in-situ lignin modification with PEGDE for reducing enzyme non-productive binding on lignins. More importantly, the synergism of 2-naphthol and PEGDE modification facilitated the enzymatic hydrolysis of AL more significantly. Its beneficial mechanism was explored by investigating the effects of in-situ lignin modification on lignin properties, including extraction yields, functional groups, and enzyme affinity of lignins. Results will give insights into establishing an efficient pretreatment of softwood biomass.

Serum amino acid metabolic profiles of ankylosing spondylitis by targeted metabolomics analysis.

BACKGROUND: Ankylosing spondylitis (AS) is a common chronic inflammatory arthritis, causing lasting back pain with progressive loss of spinal mobility. However, the exact pathogenesis of AS remains unclear. We aim to use the metabolomics analysis to characterize the metabolic profile of AS, in order to better understand the pathogenesis of AS and monitor disease activity and progression. METHODS: The ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-TQ-MS) was used for investigating the serum amino acid metabolomic profiling of 30 AS patients, in comparison with 32 rheumatoid arthritis (RA) patients and 30 healthy controls, combined with multivariate statistical analysis. Metabolite association analysis with disease activity was performed using generalized linear regression. The metabolic pathway analysis for the important metabolites was performed using MetPA and the metabolic network was constructed. RESULTS: A total of 29 amino acids and biogenic amines were detected in all participants by UPLC-TQ-MS. It showed significant amino acid differences between the AS/RA patients and control subjects. Additionally, 4-hydroxy-L-proline, alanine, γ-aminobutyric acid, glutamine, and taurine were identified as candidate markers shared by AS/RA groups. Specifically, lysine, proline, serine, and alanine were found correlated with disease activity of AS. Furthermore, the most significant metabolic pathway identified were alanine, aspartate, and glutamate metabolism, arginine and proline metabolism, aminoacyl tRNA biosynthesis and glycine, serine, and threonine metabolism. CONCLUSIONS: These preliminary results demonstrate that UPLC-TQ-MS analysis method is a powerful tool to identify metabolite profiles of AS. Research in identified disease activity-associated metabolites and biological pathways may provide assistance for clinical diagnosis and pathological mechanism of AS. Key Points • There are perturbations of serum amino acid metabolism in AS, compared with RA and healthy controls, determined by UPLC-TQ-MS. • Metabolomics pathway is used to analysis for the differential metabolites of AS. • The altered serum amino acid could monitor disease activity of AS.

Perturbations in amino acids and metabolic pathways in osteoarthritis patients determined by targeted metabolomics analysis.

Osteoarthritis (OA) is a degenerative synovial joint disease affecting people worldwide. However, the exact pathogenesis of OA remains unclear. Metabolomics analysis was performed to obtain insight into possible pathogenic mechanisms and diagnostic biomarkers of OA. Ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-TQ-MS), followed by multivariate statistical analysis, was used to determine the serum amino acid profiles of 32 OA patients and 35 healthy controls. Variable importance for project values and Student's t-test were used to determine the metabolic abnormalities in OA. Another 30 OA patients were used as independent samples to validate the alterations in amino acids. MetaboAnalyst was used to identify the key amino acid pathways and construct metabolic networks describing their relationships. A total of 25 amino acids and four biogenic amines were detected by UPLC-TQ-MS. Differences in amino acid profiles were found between the healthy controls and OA patients. Alanine, γ-aminobutyric acid and 4-hydroxy-l-proline were important biomarkers distinguishing OA patients from healthy controls. The metabolic pathways with the most significant effects were involved in metabolism of alanine, aspartate, glutamate, arginine and proline. The results of this study improve understanding of the amino acid metabolic abnormalities and pathogenic mechanisms of OA at the molecular level. The metabolic perturbations may be important for the diagnosis and prevention of OA.