Correlation between amino acid racemization and processing conditions for various wheat products,oil seed press cakes and lignin samples

The occurrence of d-amino acids in native and processed plant products is brought into context with the harshness of their treatment condition. It was found that already a small increase in processing harshness such as the milling efficiency of wheat straw or the increased pressure and duration of pumpkin seed oil extraction leads to traceable changes in the overall amino acid content as well as the racemization rate of free and protein bound amino acids. In the top position of our process harshness scale lies the strong alkali and heat-induced extraction of polyphenolic compound lignin from wood and other cellulose-rich plant fibers, e.g. wheat straw, during paper production. Since lignin accumulates in large quantities and its transformation into value-added “bio” products necessitates the recovery of native, functionally preserved lignin, milder pulping methods gain increasing interest. An unexpected drawback of such mild extraction conditions is however the high nitrogen content of such lignin products, which further increase with increasing mildness of the pulping procedure. The presence of amide bands in the FT-IR spectra of such mildly processed lignin has revealed that this nitrogen originated from co-extracted proteins and peptides. The total amino acid content as well as the free amino acid content and the degree of racemization was determined by gas chromatography–ion trap mass spectrometry (GC–Iontrap MS) employing enantiomer labeling for quantification. Cross-determination of the average amino acid content was calculated from nitrogen values obtained by elemental analysis and correlation factors were calculated from measured and calculated data. Since those amino acids with two chiral centers, such as isoleucine, threonine and hydroxyproline exhibit the highest possible diversity in terms of their relative amount to one another as well as their internal enantiomer distribution, this set of two-centered amino acids provided very distinct amino acid pattern, which proofed to be characteristic for the type of plant material as well as the harshness of the different processing conditions.     

麦秸秆的氢氧化钙预处理及酶解试验研究

采用氢氧化钙对麦秸秆进行预处理,以酶解还原糖得率为目的,分别优化预处理及酶解条件。结果表明,氢氧化钙预处理麦秸秆的最佳条件是:Ca(OH)2添加量为0.06g/g(对秸秆),固液比为1:10,在120℃下反应时间为2h;最佳酶解条件是:温度50℃,pH4.8,纤维素酶17FPU/g(对秸秆),木聚糖酶160IU/g,在添加0.15g/g(对秸秆)Tween80条件下,酶解液中还原糖质量浓度为62.32g/L,酶解还原糖得率达85.23%。     

Direct ethanol production from rice straw by coculture with two high-performing fungi

To develop efficient and economical direct ethanol production from fine rice straw crashed mechanically, two high-performing fungi, which can secret hyperactive cellulases and/or ferment effectively various sugars, were selected from some strains belong to Mucor circinelloides preserved in our laboratory. The simultaneous saccharification and fermentation (SSF) by coculture with these fungi was investigated. The screening of high-performing fungi resulted in the selection of NBRC 4572 as an ethanol-producing fungus and NBRC 5398 as a cellulase-secreting fungus. The strain 4572 produced ethanol aerobically from glucose and xylose in high yields of 0.420 g/g at 36 h and 0.478 g/g at 60 h, respectively, but secreted fairly low cellulases. On the other hand, the strain 5398 also produced ethanol from glucose in yield of 0.340 g/g though it had a little growth in xylose culture. However, it secreted hyperactive cellulases that are essential for hydrolysis of rice straw in culture and the maximum activities of endo-β-glucanase and β-glucosidase were 2.11 U/L and 1.47 U/L, respectively. In SSF of rice straw by coculture with two fungi selected, the ethanol production reached 1.28 g/L after 96 h when the inoculation ratio of the strain 5398 to the strain 4572 was 9.     

小麦秸秆催化液化工艺研究

常温常压下小麦秸秆催化液化制绿色化学品。分别研究了小麦秸秆在甲醇、乙醇、丙三醇和丁醇中的液化效果,考察了甲醇和苯酚的混合体系下液化时间与不同催化剂对液化产率的影响。结果表明,常温常压下,4种醇对小麦秸秆的液化产率的高低顺序:甲醇>乙醇>丙三醇>丁醇,甲醇的液化产率最高,达到17.23%,可以作为木质素液化的有效试剂。甲醇和苯酚混合液化体系的液化产率可达到24.52%,以对甲苯磺酸作为催化剂液化产率可达到28.40%。     

稻草苯酚液化树脂胶的制备及性能研究

用苯酚作为介质使稻草液化,将稻草中的纤维素、半纤维素和木质素转化成具有一定生物活性的液态物质,制备一种新型胶黏剂。经过TG-DSC分析,其固化温度为116.3℃,比普通的酚醛树脂胶低很多,经红外光谱分析比较表明,稻草液化胶与酚醛胶具有十分相似的IR特征峰。     

EFFECT OF PRETREATMENT CONDITIONS ON STRUCTURAL CHARACTERISTICS OF WHEAT STRAW

Structural characteristics of lignocellulosic biomass such as surface area, pore volume, crystallinity, hemicellulose, and lignin content significantly affect the yield of fermentable sugars for bioethanol production. In the present work, the effect of dilute acid pretreatment was studied on structural characteristics of wheat straw, using different combinations of process variables (temperature, time, and acid concentration). Pretreated wheat straw (PWS) exhibited higher available surface area and pore volume along with low hemicellulose and lignin content. Crystallinity index (CrI) of biomass at different pretreatment conditions showed an increased trend followed by sharp decrease at high temperature (190°C) conditions. Maximum increase in surface area (7.1 m²/g compared to 4.0 m²/g for untreated wheat straw) was obtained at pretreatment conditions of 180°C temperature, 0.5% (v/v) acid, and 7 min time. SEM imaging of biomass revealed that pore breaking, compression of pores, and partial pore blocking in the case of high temperature (190°C) pretreatment conditions may be the reason behind decreased surface area of biomass. FT-IR analysis showed almost complete hemicellulose removal and acid-soluble lignin removal after dilute acid pretreatment but insufficient removal of acid insoluble lignin.

[Supplementary material is available for this article. Go to the publisher's online edition of Chemical Engineering Communications for the following free supplemental resource: figure showing XRD pattern of biomass with respect to different pretreatment conditions.]     

Investigation of the effect of temperature and alkaline concentration on the solubilization of phenolic acids from dilute acid-pretreated wheat straw

This work deals with the investigation of the effect of alkaline concentration and temperature on the solubilization of phenolic materials from wheat straw, an abundant agricultural waste found in Turkey. The solid residue obtained after dilute acid pretreatment of wheat straw (SPWS) was treated by alkaline to solubilize the lignin to phenolic acids. Four different alkaline concentrations at 120 °C and seven different temperatures with 2 M NaOH were evaluated for the degree of solubilization of the phenolic materials, and the antioxidant activities of the soluble phenolic materials were determined. It was found that coumaric and ferulic acids were the major phenolic acids in all of the conditions tested. The highest antioxidant capacity of the hydrolysate of SPWS was obtained with 2 M NaOH at 150 °C where DPPH*, FRAP and TEAC values were found to be 3.23, 10.27 and 13.70 μmol/g WS, respectively.     

吐温-80及碱预处理对饲用稻草木质素含量和纤维素酶解产糖的影响

探讨了添加1‰吐温-80非离子表面活性剂和不同浓度碱预处理对稻草秸秆木质素及纤维素的影响,并对预处理前后的稻草进行了X射线衍射光谱(XRD)分析,从结晶度的变化综合分析了预处理对纤维素酶解的影响。实验结果表明:在30℃下添加1‰吐温-80非离子表面活性剂时,用4%NaOH预处理稻草秸秆,木质素含量降至6.5%(较未处理稻草下降了41.9%),灰分值仅占6.9%,具有较好的粗饲料价值;在121℃(0.1 MPa)下添加1‰吐温-80非离子表面活性剂时,用4%NaOH预处理稻草秸秆,木质素含量降至2.8%(较未处理稻草下降了74.5%),酶解还原糖达到393.9 mg/g,纤维素糖化率为59.3%(较未处理稻草提高了2.4倍)。XRD分析显示,在较温和的条件下,低浓度碱预处理稻草秸秆,对纤维素结晶区带来的影响相对于无定形区弱,不足以引起纤维素结晶度的降低。     

Effects of pretreatment temperature and alkali concentration on the composition of alkali-soluble lignins from wheat straw

A new rapid method of two step precipitation for isolation of alkali-soluble lignins with relatively free of polysaccharides from wheat straw was proposed in this study. The isolated alkali-soluble lignin fractions LA contained rather low amounts of neutral sugars (0.7–1.0%) and had low average molecular weights (960–1440 Da). The isolated lignin fractions LA contained roughly equal amounts of guaiacyl (G) and syringly (S) units with relatively fewer p-hydroxyphenyl (H) units, and appeared to be closely associated to phenolic acids and glucuronic acid or 4-O-methylglucuronic acid. The chemical compositions in each of the fractions are reported. The physico-chemical properties and structure features of these lignin fractions LA were characterized by UV-, IR-, ¹³C-NMR-spectroscopy, and alkaline nitrobenzene oxidation. © 1996 John Wiley & Sons, Inc.     

Role of phenolic compounds in the antialgal activity of barley straw

Barley straw decomposing in well-aerated water releases a substance(s) that inhibits algal growth. Phenolic compounds are toxic to algae but are unlikely to be present in sufficient quantities to account for the extended antialgal action of straw. However, straw is antialgal under conditions that may promote oxidation of phenolic hydroxyl groups to quinones; tannins are antialgal under similar conditions. The toxicity of authentic quinones towardsMicrocystis is confirmed; the quinones are some 10³ times more antialgal than phenolic acids. The possibility that oxidized lignin derivatives may be involved in straw toxicity towards algae is discussed.     

麦草木素在臭氧处理中的作用行为

采用FTIR和1H-NMR研究了麦草木素在臭氧处理中的作用机理。结果表明,在麦草木素臭氧处理中,苯环开裂,愈创木基较易降解,对羟苯基发生降解,酚羟基增加,甲氧基减少,酯键断裂,发色基团、助色基团减少。     

氨预处理对大豆秸秆纤维素酶解产糖影响的研究

为了提高大豆秸秆酶解产糖能力, 以利于从大豆秸秆中提取生物降解性塑料的原料 ?? 乳酸, 对大豆秸秆纤维素预处理过程的影响因素进行了探索,对预处理前后大豆秸秆的物理结构变化、化学成分变化及预处理条件对大豆秸秆酶水解产糖的影响进行了研究。研究结果表明,粉碎结合氨处理对大豆秸秆酶水解影响较大,较适宜的预处理条件为大豆秸秆粉碎至 140 目,10%氨水处理 24h。经过预处理后大豆秸秆纤维素含量提高 70.27%, 半纤维素含量下降 41.45%, 木质素含量下降 30.16%, 有利于大豆秸秆酶解产糖。     

麦草碱木质素的过氧化氢氧化氨解 Ⅱ.氧化氨解对木质素主要官能团的影响

研究了麦草碱木质素的过氧化氢氧化氨解对主要官能团的影响。结果表明过氧化氢用量、反应温度和时间对氧化氨解木质素的甲氧基、酚羟基和羧基含量均有明显的影响 ,在反应中甲氧基和酚羟基含量下降 ,而羧基含量呈上升趋势。木质素的甲氧基、羧基含量与总氮、有效氮含量均呈较好的线性关系。     

醋酸预水解对稻草化学成分及酶水解性能的影响

研究了醋酸预处理对稻草主要化学成分及酶水解糖化效率的影响。在160℃下以不同的醋酸用量(0～4%)对稻草进行处理,预处理后稻草的Klason木质素含量基本保持不变,约60%的酸溶木质素被脱除;灰分含量(质量分数)约下降30%,灰分中SiO2则几乎全部保留在预处理浆料中。预处理醋酸用量的增加对酸溶木质素和灰分含量的变化均无显著影响。预处理后高聚糖的降解程度随醋酸用量的增加而上升,其中半纤维素的降解程度尤为显著,阿拉伯聚糖、半乳聚糖大量溶出。对经醋酸预处理稻草的酶水解研究表明,预处理中醋酸用量的增加无助于酶水解液中还原糖得率的提高。稻草于160℃下经不添加醋酸的自水解预处理后,其酶解还原糖得率均高于经醋酸预处理的稻草,当纤维素酶用量为40 FPU/g(对底物)时,稻草中高聚糖的酶水解转化效率最高,葡聚糖、木聚糖的转化率分别为67.8%和45.3%,总糖转化率为58.8%。     

Enhanced ethanol production from enzymatically treated steam‐exploded rice straw using extractive fermentation

Alcohol fermentation of an enzymatic hydrolyzate of exploded rice straw was studied experimentally. Rice straw was treated under variable conditions, such as steam pressure and steaming time. The exploded rice straw was separated into water‐soluble material, methanol‐soluble lignin, Klason lignin, and a mixture of cellulose and a low molecular weight substance. The effects of steam explosion on the characteristics of the exploded rice straw were clarified from the point of view of the amounts of extractive components. Steam explosion was found to be effective for the delignification of rice straw and for increasing its susceptibility to enzyme hydrolysis and alcohol fermentation. The polysaccharides (cellulose and hemicellulose) in the rice straw treated at a steam pressure of 3.5 MPa with a steaming time of 2 min were hydrolyzed almost completely into monosaccharides, (ie glucose and xylose) by a mixture of Trichoderma viride cellulase (Meicelase) and Aspergillus aculeatus cellulase (Acucelase). The enzymatic hydrolyzate of exploded rice straw was converted into ethanol efficiently by Pichia stipitis and the ethanol yield from sugar was about 86%(w/w) of the theoretical value. The ethanol concentration in a membrane bioreactor coupled with a pervaporation system reached 50 gdm^?3 and was about five times higher than that in the culture broth. The energy efficiency (ratio of combustion energy of ethanol produced to energy for steam explosion) reached a maximum value at a pressure of 3.5 MPa for 2 min. © 2001 Society of Chemical Industry     

Improving physicochemical characteristics and anaerobic digestion performance of rice straw via ammonia pretreatment at varying concentrations and moisture levels

Rice straw physicochemical characteristics and anaerobic digestion(AD) performance via ammonia pretreatment at varying ammonia concentrations(2%, 4%, and 6%) and moisture contents(30%, 50%, 70%, and 90%)under a mild condition were investigated. The results showed that the ammonia pretreatment effectively damaged the rice straw structure, increased the soluble organic concentration, and improved rice straw hydrolysis and AD performance. After pretreatment, the ester bond and ether bond were ruptured in lignocellulose and the volatile fatty acids(VFAs) were within the range of 1457.81–1823.67 mg·L~(-1). In addition, ammonia pretreatment had high selectivity on lignin removal, resulting in a maximum lignin removal rate of 50.80%. The highest methane yield of rice straw was 250.34 ml·(g VS)~(-1) at a 4% ammonia concentration coupled with a 70% moisture content, which was 28.55% higher than that of the control. The result showed that ammonia pretreatment of rice straw is technically suitable to enhance AD performance for further application.     

碳酸钠―蒸汽爆破预处理对麦草化学成分及酶水解效率的影响

研究了碳酸钠―蒸汽爆破预处理对麦草化学成分及后续酶水解的影响。结果表明,预处理麦草浆料中木质素含量随预处理中碳酸钠用量的增大而下降,木聚糖和阿拉伯聚糖含量随碳酸钠用量的增大而上升。当碳酸钠用量增加到8%以后,继续增加碳酸钠用量,预处理麦草浆料中的葡聚糖、木聚糖、阿拉伯聚糖和木质素含量基本保持稳定。酶用量较低时,不添加碳酸钠的预处理麦草浆料酶水解葡聚糖得率最大。除不添加碳酸钠的预处理外,酶水解葡聚糖和总糖得率随木质素含量下降而提高。提高酶用量后木质素含量对预处理麦草浆料酶水解葡聚糖得率的影响变缓。     

玉米秸秆木质素的去甲基化/羟乙基化复合改性研究

利用亚硫酸钠和乙二醛对玉米秸秆木质素进行去甲基化/羟乙基化复合改性,以提高木质素的羟基含量和反应活性。通过FT-IR、TG、DSC以及乙酰化滴定等技术研究了木质素复合改性效果。结果表明:经过去甲基化/羟乙基化复合改性后的玉米秸秆木质素具有优异的活性,其总羟基质量分数较原料木质素提升了88.33%,酚羟基提升了14.70%,反应活性得到明显增强。FT-IR表征发现:复合改性从多方面提升了木质素的羟基含量,对羟基含量的增加有着较为显著的效果。热重和DSC表征发现:复合改性木质素(G-DL)相较于原料木质素降解得更加彻底,其放热峰出现在77℃,放热量达459.82 J/g,反应活性较去甲基化木质素(DL)和原料木质素更高。     

Odor‐Free Lignin from Lignocellulose by Means of High Pressure Unit Operations: Process Design,Assessment and Validation

In this work a process for the production of odor‐free lignin from wheat straw using solely water, enzymes and CO₂ is described. Wheat straw pellets are pretreated by liquid hot water and enzymatic hydrolysis in a pilot plant with a capacity of 40 L, which enables the production of 3 – 4 kg of Aquasolv lignin per batch. Dried lignin samples are further treated using supercritical CO₂, resulting into extraction of a large number of odorous free fatty acids and volatile organic compounds. All process steps can be sequentially conducted in a fixed‐bed via different sustainable solvents in a throughput regime.     

麦草酶解木素的制备影响因素的研究

在有关酶解木素研究的基础上，详细研究了球磨时间、酶用量、底物浓度、酶解时间等因素对麦草酶解木素制备的影响．考虑到球磨时间对木素结构的可能变化的影响和尽可能地获得更大的木素提取率，提出了一个合适的麦草酶解木素的提取方法。