Characterization of Acetylxylan Esterase from White-Rot Fungus Irpex lacteus

The carbohydrate esterase family 1 (CE1) in CAZy contains acetylxylan esterases (AXEs) and feruloyl esterases (FAEs). Here we cloned a gene coding for an AXE belonging to CE1 from Irpex lacteus (IlAXE1). IlAXE1 was heterologously expressed in Pichia pastoris, and the recombinant enzyme was purified and characterized. IlAXE1 hydrolyzed p-nitrophenyl acetate, α-naphthyl acetate and 4-methylumbelliferyl acetate, however, it did not show any activity on ethyl ferulate and methyl p-coumarate. We also examined the activity on partially acetylated and feruloylated xylan extracted from corncob by hydrothermal reaction. Similarly, ferulic and p-coumaric acids were not liberated, and acetic acid was only detected in the reaction mixture. The results indicated that IlAXE1 is an acetylxylan esterase actually reacted to acetyl xylan. However, since IlAXE1 was unable to completely release acetic acid esterifying xylopyranosyl residues, it is assumed that acetyl groups exhibiting resistance to deacetylation by IlAXE1 are present in corn cob xylan.     

Real-time monitoring of hemicellulose liquefaction in ethylene glycol

Xylan was used as a model material to study the liquefaction of hemicellulose in the presence of ethylene glycol. The ReactIR^TM reaction analysis system was used to monitor the entire liquefaction process online. The results showed that xylan was decomposed and transferred to liquid phase. The gel permeation chromatography results of the liquid products showed that the weight average molecular of xylan decreased signi?cantly to around 1728 g/mol after liquefaction. Gas chromatography-mass spectrometry revealed that the ethylene glycol liquefaction products from xylan include ethylene glycol and its derivatives, alcohols, aldehydes, ketones, some acids and their esters.     

Enhanced crystallization of poly(lactide) stereocomplex by xylan propionate

The effect of xylan propionate (XylPr) as a novel biomass‐derived nucleating agent on the poly(lactide) sterecomplex was investigated. Addition of XylPr to an enantiomeric blend of poly(l ‐lactide) (PLLA) and poly(d ‐lactide) (PDLA) was performed in either the solution state or molten state. The solution blend of PLLA/PDLA with XylPr was prepared by mixing equal volumes of 1 wt% XylPr/PLLA and 1 wt% XylPr/PDLA solutions in chloroform and precipitating in methanol. The solution blend with XylPr showed shorter half‐time crystallization than the solution blend without XylPr in isothermal crystallization between 80 and 140 °C, although homocrystallization occurred. Enhanced stereocomplex crystallization in the solution blend with XylPr was observed at 180 °C, where no crystallization occurred in the solution blend without XylPr. Addition of XylPr to PLLA/PDLA blend in the molten state was performed at 240 °C. Thereafter, the melt blend of PLLA/PDLA with or without XylPr was either quenched in iced water or isothermally crystallized directly from the melt. Isothermal crystallization of the melt‐quenched blend with XylPr gave a similar result to the solution blend with XylPr. In contrast, the melt‐crystallized blend with XylPr formed only stereocomplex crystals after crystallization above 140 °C. Furthermore, the melt‐crystallized blend with XylPr showed a higher crystallinity index and melting temperature than the melt‐crystallized blend without XylPr. This shows that XylPr promotes stereocomplex crystallization only when the blend of PLLA/PDLA with XylPr is directly crystallized from the molten state just after blending. © 2016 Society of Chemical Industry     

The sorption of monovalent cations onto norway spruce: Model studies using wood flour and LiCl solution

The transport of chemicals in a porous material such as wood is very complex and involves several processes: the diffusion of chemicals in the cell pores (lumen and pit pores), through the cell walls at certain conditions, and sorption of wood tissue. In the present study, batch sorption experiments were performed to examine the sorption of Li⁺ ions from an aqueous LiCl solution onto Norway spruce wood flour samples. The experimental methodology employed is suitable for differentiating the amount of ions sorbed onto the wood tissue and dissolved in the solution in wood pores. The apparent equilibrium sorption data were analyzed using two widely applied isotherm models: Langmuir and Freundlich. The results suggest that the sorption was spontaneous, and for the experimental conditions studied, probably involved several interaction types between the different functional groups of the wood and the Li⁺/Cl^? ions.     

Impact of xylan structure and lignin–xylan association on methane production from C5-sugars

Xylan biopolymers are the dominant hemicelluloses present in agricultural plant materials which have potential use in various biotechnological processes including methane production. Hence, the effect of lignin content and the structural features of xylan on anaerobic digestion were studied by using synthetic assemblies consisting of xylans and lignin models (dehydrogenation polymers). The ramification by arabinose and uronic acid was shown to be a key factor in low methane potential (BMP) from xylans and xylan–lignin assemblies. Indeed, BMP increased when xylose content was increased, and decreased when arabinose and uronic acid contents were increased. Lignin content and molecular weight were found to be the most influential parameters on the anaerobic digestion rate. Digestion rate decreased when the lignin content and molecular mass increased.     

蔗渣木聚糖-丙烯酰胺交联接枝共聚物的合成与表征

通过过硫酸铵引发丙烯酰胺与蔗渣木聚糖接枝共聚,合成了蔗渣木聚糖-丙烯酰胺接枝共聚物.考察了引发剂浓度、单体用量、反应温度和反应时间对单体转化率、接枝率和接枝效率的影响.确定较佳的反应条件为:过硫酸铵物质的量浓度0.043 mol/L,m(蔗渣木聚糖):m(丙烯酰胺)=1:1,反应温度55℃,反应时间7 h.用FTIR,...     

Estimating Glucan,Xylan, and Methylglucuronic Acids in Kraft Pulps of Eucalyptus globulus Using FT-NIR Spectroscopy and Multivariate Analysis

Abstract

Fourier transform near infrared (FT-NIR) associated with multivariate analysis was used to estimate glucan, xylan, 4-O-Methyl-α -D-glucuronic acid (MeGlcA) content, and pulp yield in kraft pulps of Eucalyptus globulus Labill. Several models were applied to correlate chemical composition in samples with the NIR spectral data by means of principal components regression (PCR) or partial least square (PLS) algorithms. Calibration models were built and validated by using all the spectral data and cross-validation methodology. The r_c ² values for the best calibration models for quantification of glucan, xylan, MeGlcA contents and pulp yield were between 0.71–0.92. The model was validated using a set of external samples. The amount of glucan (64–77%), xylan (12–18%), and MeGlcA (204–363 mmol kg pulp^–1) in pulps were predicted with a root mean square error of prediction (RMSEP) of 0.91%, 0.46%, and 15.21% for glucan, xylan, and MeGlcA, respectively. Pulp yield (in the range of 46–70%) was also predicted with good accuracy with a RMSEP of 1.63%. These results suggest that glucan, xylan, MeGlcA composition, and pulp yield in kraft pulps of E. globulus can be adequately estimated by NIR spectroscopy for laboratory or industrial applications. NIR predictions can also provide useful and cost-effective tools for the rapid screening of large numbers of samples.     

凝胶过滤色谱法研究酶解过程中木聚糖分子结构的变化

采用凝胶过滤色谱法研究了木聚糖在酶解过程中分子量分布的变化。结果表明,木聚糖酶对高分子量组分的木聚糖的降解能力较差,而主要降解分子量介于15000～3000之间组分的木聚糖,使得这部分木聚糖变为分子量更低的木聚糖组分。随着酶解时间的延长,酶解得率上升,酶解产物中低聚木糖含量增多,未被酶解的木聚糖的平均聚合度上升,当酶解时间超过4h时,这种变化趋势缓慢。随着酶解轮次的增加,酶解产物中可溶性木聚糖的含量越来越少,木聚糖被降解的难度越来越大。在实际生产中,用来作为低聚木糖生产的木聚糖其聚合度应在20～100之间,酶解时间以4h为宜,重复利用未水解木聚糖的轮次以2轮为宜。     

Properties of an Alkaline‐Tolerant,Thermostable Xylanase from Streptomyces chartreusis L1105, Suitable for Xylooligosaccharide Production

Abstract: An extracellular xylanase was purified to homogeneity from a culture of Streptomyces chartreusis L1105 by a 2‐step method of ammonium sulfate precipitation and carboxymethyl sepharose fast‐flow chromatography (CMSFF). The xylanase was purified by 6.86‐fold, with a recovery yield of 31.96%. The purified xylanase appeared as a single protein band on SDS‐PAGE with a molecular mass of about 34.2 kDa. The optimum temperature and pH of the purified xylanase activity were 70 °C and 7.2 respectively. The xylanase was more stable under alkaline conditions and retained more than 80% activity after 30 min incubation at pH 6 to 10. It also showed specific activity towards different xylans. Hydrolysis of oat‐spelt and corn‐cob xylans by the xylanase yielded xylobiose and xylotriose as principle products without the formation of xylose. These properties indicate that the purified xylanase may potentially be useful in biotechnological applications, such as xylooligosaccharide preparation. This is the first report about the purification and characterization of a xylanase from S. chartreusis.