黄孢原毛平革菌对松木、稻草和芦苇去木质化作用的研究

为确定黄孢原毛平革菌对不同植物材料的去木质化作用,以pH、干物质重、半纤维素、纤维素和木质素为主要技术指标,比较黄孢原毛平革菌对松木、稻草和芦苇降解能力的差异。松木、芦苇在发酵过程中pH呈下降趋势,稻草呈上升趋势。在干物质重、半纤维素、纤维素降解率三个指标上皆为松木〈芦苇〈稻草,在木质素降解率上则为松木〈稻草〈芦苇,且差异显著。表明黄孢原毛平革菌对不同植物材料去木质化能力有较大差异,其中芦苇的木质素降解率为13％,是三种材料中最易于被去木质化的。     

Comparison of different pretreatment methods for lignocellulosic materials. Part I: conversion of rye straw to valuable products

The conversion of lignocellulose to valuable products requires I: a fractionation of the major components hemicellulose, cellulose, and lignin, II: an efficient method to process these components to higher valued products. The present work compares liquid hot water (LHW) pretreatment to the soda pulping process and to the ethanol organosolv pretreatment using rye straw as a single lignocellulosic material. The organosolv pretreated rye straw was shown to require the lowest enzyme loading in order to achieve a complete saccharification of cellulose to glucose. At biomass loadings of up to 15% (w/w) cellulose conversion of LHW and organosolv pretreated lignocellulose was found to be almost equal. The soda pulping process shows lower carbohydrate and lignin recoveries compared to the other two processes. In combination with a detailed analysis of the different lignins obtained from the three pretreatment methods, this work gives an overview of the potential products from different pretreatment processes.     

Fermentable hexose production from corn stalks and wheat straw with combined supercritical and subcritical hydrothermal technology

Lignocellulosic wastes, including corn stalks and wheat straw, were pretreated and hydrolyzed with combined supercritical and subcritical hydrothermal technology. Soluble sugars were collected by pre-washing the crushed materials before hydrolysis. The effects of solid–liquid ratio, temperature, and reaction time on oligosaccharide production were investigated and the optimum supercritical conditions were found to be 20 mg/2.5 ml water, 384 °C, 17 s for corn stalks and 20 mg/2.5 ml water, 384 °C, 19 s for wheat straw. Subsequent subcritical processing of the hydrolyzate (with or without the water extract) from supercritical treatment was guided by a previous analysis of cellulose hydrolysis kinetics. The highest yield of fermentable hexoses from corn stalks (27.4% of raw material) was obtained at 280 °C, 27 s, and from wheat straw (6.7% of raw material) at 280 °C, 54 s. This study provides novel key parameters for fermentable hexose production from lignocellulosic feedstocks using combined supercritical and subcritical hydrothermal treatment.     

Effect of dilute acid pretreatment on the saccharification and fermentation of rye straw

This research shows the effect of dilute acid pretreatment with various sulfuric acid concentrations (0.5–2.0% [wt/vol]) on enzymatic saccharification and fermentation yield of rye straw. After pretreatment, solids of rye straw were suspended in Na citrate buffer or post-pretreatment liquids (prehydrolysates) containing sugars liberated after hemicellulose hydrolysis. Saccharification was conducted using enzymes dosage of 15 or 25 FPU/g cellulose. Cellulose saccharification rate after rye straw pretreatment was enhanced by performing enzymatic hydrolysis in sodium citrate buffer in comparison with hemicellulose prehydrolysate. The maximum cellulose saccharification rate (69%) was reached in sodium citrate buffer (biomass pretreated with 2.0% [wt/vol] H₂SO₄). Lignocellulosic complex of rye straw after pretreatment was subjected to separate hydrolysis and fermentation (SHF) or separate hydrolysis and co-fermentation (SHCF). The SHF processes conducted in the sodium citrate buffer using monoculture of Saccharomyces cerevisiae (Ethanol Red) were more efficient compared to hemicellulose prehydrolysate in respect with ethanol yields. Maximum fermentation efficiency of SHF processes obtained after rye straw pretreatment at 1.5% [wt/vol] H₂SO₄ and saccharification using enzymes dosage of 25 FPU/g in sodium citrate buffer, achieving 40.6% of theoretical yield. However, SHCF process using cocultures of pentose-fermenting yeast, after pretreatment of raw material at 1.5% [wt/vol] H₂SO₄ and hydrolysis using enzymes dosage of 25 FPU/g, resulted in the highest ethanol yield among studied methods, achieving 9.4 g/L of ethanol, corresponding to 55% of theoretical yield.     

Evaluation of effectiveness of pretreating rice straw with n-butylamine for improvement of sugar yield

Summary n-Butylamine (n-BA) pretreatment extracted a part of the holocellulose (cellulose and hemicellulose) in rice straw into the liquid phase, as a mixture of oligosaccharides and a small amount of monosaccharides. However, there was loss of sugars resulting mainly from decomposition of monomers by a long exposure to a high n-BA concentration. Approximately 70% of the total sugars in the pretreatment solutions was converted enzymatically into reducing sugars (mainly monomers). On the other hand, more than 90% of holocellulose in the residual rice straw after the optimal pretreatment was solubilized enzymatically in 120 h of reaction time with 10 w/v% substrate and 6 mg protein/ml cellulase. The main action of n-BA on rice straw was delignification, and highly crystalline cellulose was not swollen. Thus the enhancement of the enzymatic solubilization rate of rice straw appeared to be due to the increase of surface area accessible to the enzyme by delignification. It was demonstrated by the relationship of the vapour-liquid equilibrium of the n-BA/water system that the n-BA used was recovered easily. The loss of n-BA, at most, was 30% in the case of the weight ratio of n-BA to rice straw of 0.1.     

Bioconversion and biotransformation of coir pith for economic production of Pleurotus florida: chemical and biochemical changes in coir pith during the mushroom growth and fructification

Coir pith represents ∼50% of the waste from the coir industries and was tested for its potential in serving as a growth substrate for the production of species of oyster mushroom, Pleurotus florida. Due to its high lignin (∼48%) content and amorphous powdery nature, coir pith supported poor mushroom mycelial growth and yields were considerably low (∼25% bioconversion efficiency). Pre-treating coir pith with hot water did not prove economical to produce the mushroom yields. Acid swelling and alkali delignification of coir pith though served to change the structure of coir pith; the mushroom yields were not improved. Amendment of coir pith with rice (Oryza sativa) straw and horse gram (Dolichos biflorus) plant residue tended to greatly modify the physical characteristics of the inoculated mushroom bed. Such a supplementation of coir pith growth substrate resulted in production of mushroom yields with 110–125% bioconversion efficiency. Implications of supplementing coir pith with rice straw/horse gram plant residue in terms of holocellulose:lignin ratio are discussed. Sensorially, the mushrooms so produced did not differ from that on rice straw, the economic growth substrate recommended for production of the mushroom yields on commercial scale. Changes in cellulose, hemicellulose and lignin contents of coir pith amended with rice straw were studied. Cellulase, hemicellulase and protease enzyme activities in the amended coir pith substrate showed a continuous increase from inoculation till the end of fructification, whereas laccase activity decreased during fructification, in consonance with decreased lignin degradation during fructification.     

Screening of a fungus capable of powerful and selective delignification on wheat straw

Aims: To screen and characterize a novel fungus with powerful and selective delignification capability on wheat straw. Methods and Results: A fungus capable of efficient delignification under solid‐state fermentation (SSF) conditions on wheat straw was screened. After 5 days of incubation, 13·07% of the lignin was removed by fungal degradation, and 7·62% of the holocellulose was lost. Furthermore, 46·53% of the alkali lignin was removed after 2 days of liquid fermentation. The fungus was identified as Fusarium concolor based on its morphology and an analysis of its 18S rDNA gene sequence. The molecular weight distribution of lignin was evaluated by gel permeation chromatography. Enzyme assay indicated that the fungus produced laccase, cellobiose dehydrogenase, xylanase and cellulase during the incubation period. Intracellular lignin peroxidase, manganese peroxidase and laccase were produced during liquid fermentation. Conclusions: We have successfully screened a fungus, F. concolor, which can efficiently degrade the lignin of wheat straw, with slight damage to the cellulose, after 5 days of SSF. Significance and Impact of the Study: The newly isolated strain could be used in pretreatment of lignocellulose materials prior to biopulping, bioconversion into fuel and substrates for the chemical industry.     

TCF bleaching of wheat straw pulp using ozone and xylanase. Part B: kinetic studies

The reaction kinetics of ozone bleaching of wheat straw pulp has been studied for the first time. The results were compared with eucalyptus pulp in order to know that both raw materials have a similar behaviour. Ozone treatments were carried out in a special reactor at low consistency (0.5% o.d.p.). The main variables were consumption of ozone by the pulp and application of a xylanase treatment (X) prior to the oxygen stage (O). The responses measured were kappa number, viscosity and brightness, to give the kinetic expressions for delignification, cellulose degradation and elimination of chromophore groups, along with calculation of selectivity. Cellulose degradation and elimination of lignin and chromophore groups show first-order kinetics in all cases. The kinetics of the enzyme pre-treatment effect shows similar behaviour in both raw materials, although the constants of delignification and elimination of chromophore are higher in straw pulp.     

Effect of ozonolysis pretreatment on enzymatic digestibility of wheat and rye straw

Wheat and rye straws were pretreated with ozone to increase the enzymatic hydrolysis extent of potentially fermentable sugars. Through a 2(5-1) factorial design, this work studies the influence of five operating parameters (moisture content, particle size, ozone concentration, type of biomass and air/ozone flow rate) on ozonization pretreatment of straw in a fixed bed reactor under room conditions. The acid insoluble lignin content of the biomass was reduced in all experiments involving hemicellulose degradation. Near negligible losses of cellulose were observed. Enzymatic hydrolysis yields of up to 88.6% and 57% were obtained compared to 29% and 16% in non-ozonated wheat and rye straw respectively. Moisture content and type of biomass showed the most significant effects on ozonolysis. Additionally, ozonolysis experiments in basic medium with sodium hydroxide evidenced a reduction in solubilization and/or degradation of lignin and reliable cellulose and hemicellulose degradation.     

Effect of peracetic acid, sodium hydroxide and phosphoric acid on cellulosic materials as a pretreatment for enzymatic hydrolysis

Crystalline cellulose and cellulosic wastes have been treated with various concentrations of peracetic acid and other reagents at 100°C for various times, washed with water, ethanol and air dried. For each treated cellulose, the degree of enzymatic solubilization was measured with Trichoderma viride cellulase [1,4-(1,3;1,4)-β-d-glucan 4-glucanohydrolase, EC 3.2.1.4]. Cellulosic wastes such as sunflower stalks, wheat straw and sugar-cane bagasse were solubilized effectively by the enzyme. Delignification of wheat straw with 1% sodium hydroxide and treatment of this straw with peracetic acid enhanced the degree of enzymatic solubilization. Infrared spectra of the untreated and treated cellulosic wastes were recorded.     

A comparison of chemical pretreatment methods for improving saccharification of cotton stalks

The effectiveness of sulfuric acid (H(2)SO(4)), sodium hydroxide (NaOH), hydrogen peroxide (H(2)O(2)), and ozone pretreatments for conversion of cotton stalks to ethanol was investigated. Ground cotton stalks at a solid loading of 10% (w/v) were pretreated with H(2)SO(4), NaOH, and H(2)O(2) at concentrations of 0.5%, 1%, and 2% (w/v). Treatment temperatures of 90 degrees C and 121 degrees C at 15 psi were investigated for residence times of 30, 60, and 90 min. Ozone pretreatment was performed at 4 degrees C with constant sparging of stalks in water. Solids from H(2)SO(4), NaOH, and H(2)O(2) pretreatments (at 2%, 60 min, 121 degrees C/15 psi) showed significant lignin degradation and/or high sugar availability and hence were hydrolyzed by Celluclast 1.5L and Novozym 188 at 50 degrees C. Sulfuric acid pretreatment resulted in the highest xylan reduction (95.23% for 2% acid, 90 min, 121 degrees C/15 psi) but the lowest cellulose to glucose conversion during hydrolysis (23.85%). Sodium hydroxide pretreatment resulted in the highest level of delignification (65.63% for 2% NaOH, 90 min, 121 degrees C/15 psi) and cellulose conversion (60.8%). Hydrogen peroxide pretreatment resulted in significantly lower (p相似文献   

汽爆秸秆漆酶协同作用提取木质素

组分分离是秸秆炼制的关键技术。本文建立了汽爆耦合漆酶协同作用工艺,研究其对秸秆物理形态、化学组成以及木质素碱提取过程的影响。研究结果表明汽爆破坏秸秆表面致密结构,提高比表面积,促进漆酶对秸秆木质素的氧化作用;红外分析表明,漆酶破坏了汽爆秸秆中半纤维素酯键,且愈创木基吸收峰减弱,漆酶削弱了木质素与纤维素间相互作用;汽爆漆酶协同作用后的秸秆木质素提取率提高约20%(70℃,120 min)。Nuclei Growth模型分析温和条件下秸秆木质素提取过程,动力学结果表明,汽爆漆酶协同预处理增加了汽爆秸秆木质素碱提过程中反应起始作用位点,并提高了该过程对温度的敏感性。汽爆-漆酶协同预处理是一种有效的分离木质素的方法,将在木质纤维素原料的生物炼制中发挥重要作用。     

Transformation of14C labelled plant components in soil in relation to immobilization and remineralization of15N fertilizer

Summary Uniformly¹⁴C labelled glucose, cellulose and wheat straw and specifically¹⁴C labelled lignin component in corn stalks were aerobically incubated for 12 weeks in a chernozem soil alongwith¹⁵N labelled ammonium sulphate. Glucose was most readily decomposed, followed in order by cellulose, wheat straw and corn stalk lignins labelled at methoxyl-, side chain 2-and ring-C. More than 50% of¹⁴C applied as glucose, cellulose and wheat straw evolved as CO₂ during the first week. Lignin however, decomposed relatively slowly. A higher proportion of¹⁴C was transformed into microbial biomass whereas lignins contributed a little to this fraction.After 12 weeks of incubation nearly 60% of the lignin¹⁴C was found in humic compounds of which more than 70% was resistant to hydrolysis with 6N HCl. Maximum incorporation of¹⁵N in humic compounds was observed in cellulose amended soil. However, in this case more than 80% of the¹⁵N was in hydrolysable forms.Immobilization-remineralization of applied¹⁵N was most rapid in glucose treated soil and a complete immobilization followed by remineralization was observed after 3 days. The process was much slow in soil treated with cellulose, wheat straw or corn stalks. More than 70% of the newly immobilized N was in hydrolysable forms mainly reepresenting the microbial component.Serial hydrolysis of soil at different incubation intervals showed a greater proportion of 6N HCl hydrolysable¹⁴C and¹⁵N in fractions representing microbial material.¹⁴C from lignin carbons was relatively more uniformly distributed in different fractions as compared to glucose, cellulose and wheat straw where a major portion of¹⁴C was in easily hydrolysable fractions.     

Progress in biopulping of non-woody materials: Chemical, enzymatic and ultrastructural aspects of wheat straw delignification with ligninolytic fungi from the genus Pleurotus

Abstract: During screening of basidiomycetes for wheat straw delignification, considerable lignin degradation with a limited attack to cellulose was attained with Pleurotus eryngii . Straw solid-state fermentation (SSF) was optimized, and the enzymatic mechanisms for lignin degradation were investigated. No lignin peroxidase was detected under liquid or SSF conditions, but high laccase and aryl-alcohol oxidase levels were found. The latter enzyme has been fully characterized in PI. eryngii and it seems to be involved in a cyclic redox system for H₂0₂ generation from aromatic compounds. Results obtained using homoveratric acid suggest that Pleurotus laccase could be involved in degradation of phenolic and non-phenolic lignin moieties. Histological and ultrastructural studies provided some general morphological characteristics of the fungal attack on wheat straw. Whereas a simultaneous degradation pattern was observed in straw treated with Phanerochaete chrysosporium , PI. eryngii caused partial degradation of middle lamella and separation of individual sclerenchymatic fibers. When these straw samples were subjected to refining tests, energy saving after biological treatment was the highest in the case of straw treated with PI. eryngii , which also produced the lowest substrate loss. From these results, a correlation between preferential removal of lignin, separation of sclerenchymatic fibers and pulping properties was provided during fungal treatment of wheat straw.     

Spatial and Temporal Variation of Roots, Arbuscular Mycorrhizal Fungi, and Plant and Soil Nutrients in a Mature Pinot Noir (Vitis vinifera L.) Vineyard in Oregon, USA

Soil and crop management practices may influence biomass growth and yields of cotton (Gossypium hirsutum L.) and sorghum (Sorghum bicolorL.) and sequester significant amount of atmospheric CO₂in plant biomass and underlying soil, thereby helping to mitigate the undesirable effects of global warming. This study examined the effects of three tillage practices [no-till (NT), strip till (ST), and chisel till (CT)], four cover crops [legume (hairy vetch) (Vicia villosa roth), nonlegume (rye) (Secale cerealeL), hairy vetch/rye mixture, and winter weeds orno covercrop], and three N fertilization rates (0, 60–65, and 120–130 kg N ha ^–1) on the amount of C sequestered in cotton lint (lint + seed), sorghum grain, their stalks (stems + leaves) and roots, and underlying soil from 2000 to 2002 in central Georgia, USA. A field experiment was conducted on a Dothan sandy loam (fine-loamy, kaolinitic, thermic, Plinthic Kandiudults). In 2000, C accumulation in cotton lint was greater in NT with rye or vetch/rye mixture but in stalks, it was greater in ST with vetch or vetch/rye mixture than in CT with or without cover crops. Similarly, C accumulation in lint was greater in NT with 60 kg N ha ^–1 but in stalks, it was greater in ST with 60 and 120 kg N ha ^–1 than in CT with 0 kg N ha ^–1. In 2001, C accumulation in sorghum grains and stalks was greater in vetch and vetch/rye mixture with or without N rate than in rye without N rate. In 2002, C accumulation in cotton lint was greater in CT with or without N rate but in stalks, it was greater in ST with 60 and 120 kg N ha ^–1 than in NT with or without N rate. Total C accumulation in the above- and belowground biomass in cotton ranged from 1.7 to 5.6 Mg ha ^–1 and in sorghum ranged from 3.4 to 7.2 Mg ha ^–1. Carbon accumulation in cotton and sorghum roots ranged from 1 to 14% of the total C accumulation in above- and belowground biomass. In NT, soil organic C at 0–10 cm depth was greater in vetch with 0 kg N ha ^–1 or in vetch/rye with 120–130 kg N ha ^–1 than in weeds with 0 and 60 kg N ha ^–1 but at 10–30 cm, it was greater in rye with 120–130 kg N ha ^–1 than in weeds with or without rate. In ST, soil organic C at 0–10 cm was greater in rye with 120–130 kg N ha ^–1 than in rye, vetch, vetch/rye and weeds with 0 and 60 kg N ha ^–1. Soil organic C at 0–10 and 10–30 cm was also greater in NT and ST than in CT. Since 5 to 24% of C accumulation in lint and grain were harvested, C sequestered in cotton and sorghum stalks and roots can be significant in the terrestrial ecosystem and can significantly increase C storage in the soil if these residues are left after lint or grain harvest, thereby helping to mitigate the effects of global warming. Conservation tillage, such as ST, with hairy vetch/rye mixture cover crops and 60–65 kg N ha ^–1 can sustain C accumulation in cotton lint and sorghum grain and increase C storage in the surface soil due to increased C input from crop residues and their reduced incorporation into the soil compared with conventional tillage, such as CT, with no cover crop and N fertilization, thereby maintaining crop yields, improving soil quality, and reducing erosion.     

Correlating the effect of pretreatment on the enzymatic hydrolysis of straw

Avicell, Alkali-treated straw cellulose (ATSC), and wheat straw were ball-milled to reduce crystallinity; wheat straw was delignified by hot (120 degrees C) sodium hydroxide solutions of various concentrations. The physically and chemically pretreated cellulosic materials were hydrolyzed by the cellulases of Fusarium oxysporum strain F3. Enzymic hydrolysis data were fitted by the hyperbolic correlation of Holtzapple, which involves two kinetic parameters, the maximum conversion (X(max)), and the enzymic hydrolysis time corresponding to 50% of X(max) (t(1/2)). An empirical correlation between X(max) and cellulose crystallinity, lignin content, and degree of delignification has been found under our experimental conditions. Complete cellulose hydrolysis is shown to be possible at less than 60% crystallinity indices or less than 10% lignin content.     

Optimal conditions for pretreatment of rice straw with n-butylamine for enzymatic solubilization

Summary Three different pretreatment methods with n-butylamine (n-BA) were used to obtain fermentable sugars in a high yield from rice straw. The optimal conditions of each method were as follows: treating at boiling point for 1 h under refluxing in 10 w/w% n-BA with the weight ratio of n-BA to original rice straw more than 1.0, autoclaving at 120°C for 1 h in 1 w/w% n-BA with the weight ratio more than 0.1, and wetting for 2 h with the circulating condensate of the vapour evaporated from 2.5 w/w% n-BA with the weight ratio more than 0.8. Soaking rice straw with n-BA before the above pretreatments was not needed. For the circulation pretreatment, the overall cumulative yield of total sugars (70% of cellulose and hemicellulose in original rice straw) was best for both pretreatment and enzymatic solubilization steps, because there was no decomposition of monosaccharides during the pretreatment. Furthermore, the optimal degree of delignification for enzymatic solubilization of the pretreated rice straw was approximately 60% of lignin in the original.     

Influence of solid loading on enzymatic hydrolysis of steam exploded or liquid hot water pretreated olive tree biomass

Olive tree pruning biomass, pretreated by either liquid hot water or steam explosion under selected conditions, was used as a substrate for enzymatic hydrolysis. The pretreated material was further submitted to alkaline delignification, the objective being to improve hydrolysis yields as well as increasing cellulose content in the pretreated feedstock. The enzymatic hydrolysis of pretreated residues was performed using a commercial cellulase mixture supplemented with β-glucosidase, using a solid loading range from 2 to 30% (w/v). The influence of substrate concentration on the enzymatic hydrolysis yield and on glucose concentration was studied. Comparative results with and without a delignification step are presented. Enzymatic hydrolysis at high substrate concentration (≥20%) is possible, yielding a concentrated glucose solution (>50 g/L). Nevertheless, a cellulose fraction of the pretreated residue remains unaltered.     

木质素降解菌的筛选及混合菌发酵降解秸秆的研究

农作物秸秆是农业生产的副产品,也是一项重要的生物资源。由于其成分结构的特殊性所导致的难降解问题,一直成为了转化利用秸秆的难题。目前,利用混合菌将秸秆纤维素转化为蛋白质、乙醇、乙酸、乳酸等研究已逐渐为人们所重视。本文通过马铃薯琼脂平板培养、马铃薯液体摇瓶培养和稻草秸秆固态发酵,从6株常见的食用白腐菌中筛选出了生长优势较强、产漆酶酶活高的平菇HF。为了让秸秆得到更好的降解和利用,采用平菇和康氏木霉二步混合发酵法;通过不同的组合方式,发现H6-T10组合得出的降解效果最好,其木质素降解率达到44.77%,纤维素降解率达到41.48%。     

Novel renewable ionic liquids as highly effective solvents for pretreatment of rice straw biomass by selective removal of lignin

Cholinium amino acids ionic liquids ([Ch][AA] ILs), a novel type of bio‐ILs that can easily be prepared from renewable biomaterials, were investigated for pretreatment of rice straw by selective extraction of lignin from this abundant lignocellulosic biomass material. Of the eight ILs examined, most were demonstrated to be excellent pretreatment solvents. Upon pretreatment using these ILs, the initial saccharification rates of rice straw residues were substantially improved as well as the extent to which polysaccharides could be digested (>90% for cellulose and >60% for xylan). Enzymatic hydrolysis of pretreated rice straw by Trichoderma reesei cellulase/xylanase furnished glucose and xylose with the yields in excess of 80% and 30%, respectively. Detailed spectroscopic characterization showed that the enhancement of polysaccharides degestibility derived mainly from delignification rather than changes in cellulose crystallinity. The yields of fermentable reducing sugars were significantly improved after individual optimization of pretreatment temperature and duration. With [Ch][Lys] as the solvent, the sugar yields of 84.0% for glucose and 42.1% for xylose were achieved after pretreatment at 90°C for 5 h. The IL [Ch][Lys] showed excellent reusability across five successive batches in pretreatment of rice straw. These bio‐ILs performed as well as or better than previously investigated non‐renewable ILs, and thus present a new and environmentally friendly way to pretreat lignocellulose for production of fermentable sugars and total utilization of the biomass. Biotechnol. Bioeng. 2012; 109: 2484–2493. © 2012 Wiley Periodicals, Inc.