两段碳酸钠―氧预处理提高麦草酶水解糖化性能的研究

探讨了不同Na2CO3用量下两段碳酸钠―氧(Na2CO3-O2)预处理对麦草化学成分及酶水解效率的影响。Na2CO3-O2预处理麦草浆料得率随Na2CO3用量增大而下降,木质素脱除率随之增加。预处理后废液的pH值约为9,可有效避免碳水化合物的碱性水解和二次剥皮反应,保持较高的预处理浆料得率。预处理后浆料经过由纤维素酶、木聚糖酶和β-纤维二糖酶组合而成的混合酶水解,当预处理Na2CO3用量(以Na2O计)从12%增至18%时,预处理浆料总糖得率的增加较为显著。经20 PFU/g纤维素酶水解48 h后,总用碱量为18%的两段Na2CO3-O2预处理浆料的酶水解总糖得率为40.8%,总糖转化率为67.0%。     

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。     

亚硫酸钠预处理提高稻草酶水解糖化效率的研究

研究了亚硫酸钠预处理对稻草化学组分变化及酶水解性能的影响。结果表明,提高温度或增加Na2SO3用量可以脱除更多的木质素和半纤维素,酶水解效率也相应提高,但木质素脱除率达到50%以后,继续增强预处理条件,对酶水解糖得率无显著的促进作用。相比而言,加大Na2SO3用量更有利于使木质素溶出,提高温度更有利于使高聚糖溶出,加大Na2SO3用量比提高温度对酶水解效率的提高影响更显著。通过实验得到亚硫酸钠预处理稻草的最优条件,在温度为140℃,Na2SO3用量为16%,纤维素酶用量为20 FPU/g(对纤维素)时,总糖转化率达到最大,为74.9%,此时的总糖得率为43.5%。     

绿液预处理对棉秆化学成分及酶水解糖化的影响

绿液的主要成分是Na2CO3和Na2S,可在硫酸盐浆厂碱回收系统中循环产生。将新疆棉秆在不同温度、硫化度和用碱量下经绿液预处理后,在不同酶用量下进行酶水解,并测定酶水解液中总糖得率以评价预处理效果。结果表明,原料预处理得率随用碱量的增加而下降。适当地提高蒸煮温度和用碱量,可以增加木质素脱除量,有利于后续酶水解的进行,但过于剧烈的预处理条件将导致碳水化合物的过度降解,因而降低酶水解糖的转化率。另外,由于新疆棉秆细小,棉秆皮占全秆比例较大,原料总糖含量较低,导致最终酶水解总糖得率偏低。在温度120?C,用碱量16%,硫化度32%条件下绿液预处理,酶水解糖转化率达到最大值,当酶水解酶用量为20 FPU/g(对浆料)时,葡聚糖、木聚糖和总糖的转化率分别为74.0%、61.3%和68.5%。     

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%。     

亚硫酸氢钠预处理对杨木浆料化学成分及酶解糖化的影响

研究了亚硫酸氢钠预处理对杨木浆料化学成分及酶水解效率的影响。增加预处理试剂亚硫酸氢钠用量可以脱除更多的木质素和半纤维素,随着试剂用量的增加葡聚糖、木聚糖和总糖的酶水解得率呈现先升高后降低,然后又升高的规律。当预处理试剂用量为4％时,木质素脱除率为28．7％,酶水解总糖转化率为55．2％;继续增加试剂用量至16％时,对酶水解糖的得率无明显促进作用,反而由于高聚糖降解较多导致得率下降;当试剂用量超过20％时,酶水解糖的得率又有所上升。亚硫酸氢钠用量为24％时,木质素脱除率为61．6％,总糖的转化率达到最大,在纤维素酶用量40FPU／g时,葡聚糖、木聚糖和总糖的转化率分别为59．7％、64．6％和66．2％。     

麦草自水解过程中半纤维素和木质素的变化特性

自水解对木质纤维生物质转化利用具有重要意义,研究了自水解对麦草化学成分变化的特性。结果表明:温度和时间对麦草自水解化学成分变化有重要影响,温度170℃时,半纤维素与木质素的降解均呈现两个阶段,即保温60 min前的快速脱除阶段和60 min后的慢速脱除阶段,半纤维素脱除率分别为65.0%和16.7%,Klason木质素脱除率分别为33.0%和2.7%,酸溶木质素脱除率分别为66.1%和11.7%;自水解大大提高麦草苯醇抽出物含量,170℃保温210 min后苯醇抽出物含量达15.9%。麦草自水解具有生物炼制特点。     

氢氧化钠-硫脲-尿素水溶液高温预处理对麦草纤维酶解性能的影响研究

利用氢氧化钠-硫脲-尿素水溶液在高温条件下处理麦草纤维,通过单因素试验探究该体系对麦草纤维酶解性能的影响情况。结果表明:在用碱量(氢氧化钠计)10%、最高温度120℃、保温时间45min(纤维浓度20%)的条件下,该体系对麦草纤维酶解性能的改善效果最佳。在上述条件下,纤维中苯-醇抽提物、灰分、木质素和综纤维素的脱除率分别为65.29%、55.82%、67.80%和21.04%,同时酶解总糖含量和总糖转化率分别为45.7%和74.8%,比在相同条件下经氢氧化钠水溶液处理后纤维的相应指标增加21.5%。     

碱-氧-蒽醌蒸煮法制取麦草浆纤维素的酶解

用碱-氧-蒽醌蒸煮麦草所得纤维素为原料,研究了纤维素酶解的影响因素.结果表明:预处理后的麦草纤维素,其木质素含量较低,而酶解率和木质素脱除率均较高,在45～50℃、pH为4.4、底物与酶量之比为1:0.02、反应时间为30h、转速为100r/min时,可获得较理想的酶解率和木质素脱除率,二者分别可达74.5%和19.2%.     

自水解预处理对稻草化学成分及酶解性能的影响

研究了自水解处理对稻草秸秆主要化学成分及酶解糖化效率的影响。结果显示:在100～160℃下对稻草进行自水解预处理,酸溶木质素的脱除程度随着自水解温度的升高而增大,而Klason木质素含量几乎没有变化,几乎全部SiO2仍然保留在预处理后草片中;稻草高聚糖的降解程度随着自水解温度的升高而增加,但由于自水解液酸性较弱,大量高聚糖仍保留在草片中;自水解预处理有利于促进稻草的酶解糖化,随着自水解预处理温度的升高和酶用量的增大,酶解液中各种聚糖得率均有不同程度的提高,但自水解温度的影响显得更为重要;经160℃自水解预处理的稻草在40 FPU/g混合酶用量下,葡聚糖和木聚糖的总转化率约为68%和45%,总糖转化率近60%。     

Effect of process variables on liquid hot water pretreatment of wheat straw for bioconversion to fuel‐ethanol in a batch reactor

BACKGROUND: Crop residues as wheat straw are potential sources for fuel‐ethanol production as an alternative to current production based on starch‐ or sugar‐containing feedstocks. In this work, the effect of liquid hot water (LHW) process parameters, i.e. temperature (170 and 200 °C), residence time (0 and 40 min), solid concentration (5% and 10% (w/v)) and overpressure applied in the reactor (30 bar and no overpressure), on pretreatment of wheat straw was studied using a full factorial experimental design. Pretreatment effectiveness was evaluated based on the composition of the solid and liquid fractions obtained after filtration of pretreated material, and the susceptibility of the solid fraction to enzymatic hydrolysis (EH) using commercial cellulases. RESULTS: Statistical analysis showed that only temperature and time, within the limits of the experimental range, have a significant effect on the responses studied. While the effect of pretreatment time in hemicellulose‐derived sugar recovery in prehydrolyzate depends on temperature, EH yield was enhanced as both temperature and time were increased. Maximum EH yield was 96 g glucose per 100 g potential glucose in pretreated residue. Xylan and acetyl groups content remaining in solid residue after pretretament, which were found to be directly correlated, had a marked effect on pretreated substrate degradability. CONCLUSIONS: LHW is an effective pretreatment to enhance the potential of wheat straw as substrate for ethanol production. Maximum hemicellulose‐derived sugar recovery (53% of content in raw material) and EH yield (96% of theoretical) fall within different temperature and time intervals, suggesting separate optimization designs for these responses. Copyright © 2007 Society of Chemical Industry     

Evaluation of enzymatic hydrolysis of wheat straw pretreated by atmospheric glycerol autocatalysis

BACKGROUND: Because ethanol organosolv pulping requires high pressure and is highly volatile, an atmospheric autocatalytic glycerol organosolv pretreatment process has been investigated. Enzymatic hydrolysis of wheat straw pretreated using this method was evaluated to explore a novel, economically competitive and environmentally friendly pretreatment technology for bioconversion of lignocellulosic biomass. The method also provides economical utilization of industrial glycerol, helping to cope with the challenge of the excess production of glycerol and to further defray the cost of biodiesel production. RESULTS: With preliminary optimization of the parameters in the pretreatment process, pretreatment performed at 240 °C for 4 h with the glycerol addition of 15 g g^?1 dry feedstock and wash at 80 °C led to high recovery of cellulose (95%) and good removal of lignin (>70%), which formed, respectively, 80% and 10% of the pulp. The enzymatic hydrolysis of the pretreated wheat straw yielded 90% of theoretically achievable sugar after 24 h and 92% after 48 h. CONCLUSION: Atmospheric autocatalytic glycerol organosolv pretreatment removed significant amounts of hemicellulose and lignin without affecting good cellulose recovery. The proposed novel strategy increased the susceptible of wheat straw to enzyme attack and led to enzymatic hydrolysis that was comparable with that achieved using ethanol organosolv pretreatment. Copyright © 2007 Society of Chemical Industry     

表面活性剂耦合离子液体对稻秆酶解糖化的影响

酶解糖化是木质纤维素材料制备生物质乙醇的关键环节,因此提高稻秆等木质纤维素材料的酶解糖化效率具有重要意义。以稻秆为原料,采用表面活性剂耦合离子液体为预处理方法,考察预处理温度、时间、表面活性剂的添加比例对稻秆酶解的影响。结果表明,预处理温度为110℃、时间为60 min、表面活性剂添加比例为1%,稻秆的酶解效果最佳,与单独离子液体处理的稻秆相比,纤维转化率可提高8%～15%。同时分别通过稻秆成分分析、FTIR、XRD、SEM等对预处理前后的稻秆结构进行表征,证实预处理后酶解效率提高的合理性。     

Green Liquor Pretreatment of Mixed Hardwood for Ethanol Production in a Repurposed Kraft Pulp Mill

Abstract

The development of a new, relatively simple process, which uses green liquor (sodium carbonate and sodium sulfide) as a pretreatment for the production of ethanol is described in this article. The pulps produced by this process can be enzymatically hydrolyzed to monomeric sugars with a high overall sugar recovery. The use of green liquor for pretreatment ensures that the chemicals used during pretreatment can be recovered efficiently using proven technology and can be easily implemented in a repurposed kraft pulp mill. The yield of pulps produced by the green liquor pretreatment process is about 80% with nearly 100% cellulose and 75% xylan in retention in mixed southern hardwood. The low pH prevents the random hydrolysis of polysaccharide and secondary peeling reactions from occurring during the pretreatment, resulting in higher retention of the polysaccharides in pulp. About 35% of the lignin is removed during the green liquor pretreatment process, which is sufficient for efficient enzymatic hydrolysis. The amount of sugar produced in enzymatic hydrolysis increased with both the green liquor and enzyme charge. The increase in enzymatic hydrolysis efficiency was small as the total titrateable alkali was increased beyond 12–16%. With green liquor pretreatment at 16% Total Titrateable Alkali (TTA), the overall sugar recovery for hardwood was shown to be around 77% at a cellulase charge of 20 FPU/gm of substrate. A sugar recovery of 80% could be achieved at higher enzyme charges. These levels of sugar recovery are competitive with other pretreatments for hardwood. This novel pretreatment process can be used to repurpose kraft mills, which are being closed due to a decrease in the demand for paper in North America, for production of ethanol.     

蒸煮助剂对低用碱量硫酸盐法预处理毛竹竹屑的影响

毛竹竹屑经10%低用碱量 (以Na₂O计)、20%硫化度、160 ℃下保温1 h预处理,木质素脱除率达到62.35%,预处理物料酶水解48 h葡萄糖和木糖得率分别为56.04%和53.47%。研究了硼氢化钠、三聚磷酸钠、2-蒽醌磺酸钠3种蒸煮助剂对毛竹竹屑10%用碱量硫酸盐预处理的成分以及糖化效果影响,其中2-蒽醌磺酸钠影响最大。在10%用碱量和20%硫化度的预处理液中添加0.15%的2-蒽醌磺酸时,160 ℃下保温1 h的葡聚糖回收率和木质素脱除率分别为94.93%和68.55%,与空白对比分别提高5.45%和9.94%;预处理物料酶解48 h葡萄糖和木糖得率分别为62.88%和58.97%,与空白对比分别提高12.21%和10.29%。