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%。     

碳酸钠预处理对麦草酶水解糖化的影响

麦草是一种具有很大潜力的制取生物乙醇的可再生木质纤维素原料。文章探讨了碳酸钠预处理预浸时间、保温时间、碳酸钠用量对麦草化学成分及酶水解效率的影响。结果表明,延长碳酸钠预处理保温时间对木质素脱除无明显影响,但浆料得率和酶水解总糖转化率有所下降;合理的预浸时间为30 min,继续延长预浸时间对预处理浆料酶水解总糖转化率无促进作用;增加预处理Na2CO3用量有助于促进木质素的脱除,大部分碳水化合物保留在浆料中。在8% Na2CO3(Na2O计)用量下,麦草于80℃预浸30 min后升温至130℃,不保温所得到的浆料在纤维素酶用量为20 FPU/g(对纤维素)时,其总糖转化率为60%。     

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%。     

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％。     

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%。     

水抽提物对稀酸预处理玉米秸秆酶水解的影响

采用水抽提方法得到玉米秸秆中的水抽提液,研究水抽提液、水抽提液的稀酸水解液对水抽提玉米秸秆和稀酸预处理的水抽提玉米秸秆酶水解性能的影响。研究结果表明,与未处理玉米秸秆相比,水抽提玉米秸秆的酶水解性能有所提高,从48 h的9.88%提高到23.56%;与稀酸预处理玉米秸秆相比,稀酸预处理的水抽提玉米秸秆酶水解性能略有提高,从48 h的67.07%提高到73.44%;通过向水抽提玉米秸秆和稀酸预处理的水抽提玉米秸秆中添加水抽提液的酶水解结果表明,与未添加的空白样相比,添加水抽提液对酶水解得率的影响极小(2%以内),但水抽提液经过稀酸水解后再添加到水抽提玉米秸秆和稀酸预处理的水抽提玉米秸秆中,可以发现与未添加的空白样相比,酶水解得率大幅度降低,酶解48 h时分别下降了15.03%和13.96%,这说明水抽提液在稀酸预处理过程中产生了对酶水解有抑制作用的物质。因此,通过水抽提去除部分水抽提物可减少稀酸预处理过程中抑制物的产生,从而提高酶水解得率的能力。     

碱性臭氧预处理对稻草秸秆酶水解的影响

以稻草秸秆为原料经碱性臭氧预处理后进行酶水解,研究了处理前后稻草秸秆半纤维素、纤维素、木质素含量的变化,通过测定酶水解还原糖含量来判断预处理的效果。结果表明,碱性臭氧预处理与碱预处理相比,在稻草秸秆木质素含量与降解上没有什么差异,但酶水解糖化效果更优。经O3/2%NaOH预处理过的稻草秸秆,在pH值5.0、酶用量31.2mg.（g底物）-1、45℃条件下酶水解120h时,还原糖含量达到了902mg.（g稻草秸秆）-1,糖化率达到了92.57%。     

弱碱性过氧化预处理对稻草秸秆酶解糖化的影响

为了提高稻草秸秆的酶解糖化率,对稻草秸秆弱碱性过氧化预处理条件进行了优化。结果表明:弱碱性过氧化预处理降低了稻草秸秆中木质素的含量,提高了纤维素的含量。最优预处理条件为温度40 ℃,时间24 h,H₂O₂质量分数为2.0 %,在此条件下稻草秸秆的酶解糖化率达到了83.23 %,而在相同酶解条件下,预处理温度30 ℃、时间24 h、 2.0 % NaOH处理后稻草秸秆的酶解糖化率为70.38 %。弱碱性过氧化预处理稻草秸秆的糖化率明显高于碱性预处理稻草秸秆的糖化率。同时试验结果表明,木质素的除去率与H₂O₂质量分数有关。当H₂O₂质量分数大于2.0 %后,H₂O₂对木质素的除去选择性降低,木质素的除去率基本保持不变,却增加了半纤维素的损失。     

不同预处理方法对玉米秸秆吐温-80/酶水解的影响

比较了稀硫酸、氢氧化钠、氨水和氢氧化钙4种预处理方法对玉米秸秆吐温-80/酶水解的影响,结果表明:氢氧化钠预处理方法效果最佳,得到的总还原糖产率比未处理时提高了10.7倍.其红外光谱和广角X-谢线衍射谱图表明:经氢氧化钠预处理后,玉米秸秆中的木质素含量降低了62%,纤维素的结晶度也有所降低.     

酶水解pH值对酸性亚硫酸氨盐预处理杨木糖化效率的影响

改变酶水解p H值可以影响木质纤维生物质碳水化合物的酶水解糖化作用效果。以经酸性亚硫酸氢盐预处理的杨木浆为底物,探究了酶水解p H值对其碳水化合物转化率的影响。结果表明,预处理杨木浆的酶水解总糖得率随p H值增加呈现先升高后趋于平缓的规律,酶水解最佳p H值范围为4.8~5.4。当酶水解液p H值为4.8时,经6%亚硫酸氢钠预处理杨木浆在20 FPU/g酶用量下水解,葡聚糖和总糖转化率达到最高值,分别为91.3%和84.3%。     

竹青表面蜡质对纤维素酶解的影响研究进展

覆盖在竹子最表层的竹青蜡质层在竹子生长发育、适应外界环境方面起重要作用,同时也是阻碍生物炼制的主要抗降解屏障之一。目前,竹材的工业化加工利用大多以竹纤维为主,竹青和竹黄部分通常以加工剩余物的形式除去,不仅浪费资源,而且造成严重的环境污染。与不含蜡质层的竹肉和竹黄相比,含有蜡质层的竹青即使在预处理后其纤维素酶水解糖化效率仍十分低下。本文对竹青表皮蜡质的组成、蜡质成分对纤维素酶的相互作用以及预处理对蜡质的影响等方面研究进行综述,并探讨其存在的问题机理与研究前景。为提高以竹加工剩余物为原料的生物炼制效率提供理论依据和借鉴,为竹源天然蜡质提取及材料应用创新提供新途径。     

水热预处理竹子促进酶解的效果及其影响因素

采用间歇式水热预处理装置,研究了水热预处理用于竹子的酶解规律,探讨了不同温度、处理时间、纤维素酶添加量及原料种类对促进竹子酶解的效果及其影响。结果表明水热预处理能显著提升竹子的酶解率,在优化条件190℃、10 min水热预处理,添加15 FPU·(g葡聚糖)^-1纤维素酶,72 h葡聚糖与木聚糖酶解率分别为74.3%、54.0%,提高到原来的3.5倍和4.7倍。过高的预处理温度与过长的预处理时间都将导致木糖大量降解和部分葡萄糖降解,使单糖总量下降。纤维素酶的添加量从15 FPU·(g 葡聚糖)^-1提高到60 FPU·(g 葡聚糖)^-1,可使未作预处理和水热预处理竹子的总糖回收率分别提高21.5%和9.9%,其促进酶解的作用远低于预处理的效果,通过预处理增大酶的可及性是提高酶解率的关键。水热预处理对于生物质原料具有选择性,不同的竹子原料具有显著不同的效果。     

Effect of several factors on peracetic acid pretreatment of sugarcane bagasse for enzymatic hydrolysis

BACKGROUND: Lignocellulose should undergo pretreatment to enhance its enzymatic digestibility before being saccharified. Peracetic acid (PAA) is a strong oxidant that can remove lignin under mild conditions. The sulfuric acid in the PAA solution also can cause degradation of hemicelluloses. The objective of the present work is to investigate the effect of several factors on peracetic acid pretreatment of sugarcane bagasse. RESULTS: It was found that PAA charge, liquid/solid (l/s) ratio, temperature, time, interactions between PAA charge and l/s ratio, temperature and time, all had a very significant effect on the enzymatic conversion ratio of cellulose. The relative optimum condition was obtained as follows: PAA charge 50%, l/s ratio 6:1, temperature 80 °C and time 2 h. More than 80% of the cellulose in bagasse treated under the above conditions was converted to glucose by cellulase of 20 FPU g^?1 cellulose. Compared with H₂SO₄ and NaOH pretreatments under the same mild conditions, PAA pretreatment was the most effective for enhancement of enzymatic digestibility. CONCLUSION: PAA pretreatment could greatly enhance the enzymatic digestibility of sugarcane bagasse by removing hemicelluloses and lignin, but removal of lignin was more helpful. This study can serve as a step to further optimization of PAA pretreatment and understanding the mechanism of enhancement of enzymatic digestibility. Copyright © 2007 Society of Chemical Industry     

Comparison of ionic liquid,acid and alkali pretreatments for sugarcane bagasse enzymatic saccharification

BACKGROUND: Much attention has been given to applying ionic liquids (ILs) as an alternative pretreatment method for lignocellulosic biomass. This study aims to select the most suitable type of IL for pretreating sugarcane bagasse (SCB). The potential of ILs for pretreatment was evaluated and compared with conventional pretreatment media, acids and alkalis. The performance of the pretreatment media was evaluated based on the amount of reducing sugar produced from enzymatic saccharification, the energy requirement, and changes in the chemical structure and crystallinity index of the pretreated bagasse. RESULTS: 1‐ethyl‐3‐methylimidazolium acetate [EMIM]oAc was selected as the most suitable IL for SCB pretreatment. The optimum yields of reducing sugar obtained from [EMIM]oAc‐, alkali‐, and acid‐pretreated SCB were 69.5%, 92.8% and 41.3%, respectively. Although a lower yield of reducing sugar was obtained, [EMIM]oAc pretreatment required the least energy to pretreat 1 kg of SCB. Moreover, the percentage of SCB loss during [EMIM]oAc pretreatment was the lowest. [EMIM]oAc‐pretreated SCB also had the lowest crystallinity index (CI) with the most amorphous structure. CONCLUSION: [EMIM]oAc appears to be another option for pretreating SCB, and other issues such as the recyclability of [EMIM]oAc is worth investigating. Copyright © 2011 Society of Chemical Industry     

碱联合超高压预处理对笋壳酶解效率的影响

以竹笋壳（BS）为原料,采用单独超高压（UHP）、单独碱加热（AH）、超高压后碱加热（UHP+AT）和碱加热后超高压（AT+UHP）4种方法进行预处理,并对比分析了样品预处理前后的化学组成、扫描电镜（SEM）、晶体结构（XRD）、红外光谱（FTIR）、比表面积和孔结构及酶水解效率的变化规律。结果表明：与其他处理方法相比,AT+UHP在450MPa压强下处理效果最好。预处理后样品中木质素的脱除率为86.87%,微观表面结构松散和粗糙,结晶指数有所上升,比表面积和孔体积分别为2.590m²/g、0.010cm³/g,酶水解效率高达97.89%。UHP+AT与AT+UHP预处理效果差异不明显,其酶解效率达到96.94%。因此,碱联合超高压处理是生物燃料生产中生物质预处理的一种潜在选择。     

Effect of enzymatic pretreatment on acid fermentation of food waste

Although food waste is a valuable carbon source for biological nutrient removal systems with low organic wastewater because of high C/N and C/P ratios, it must be pretreated to promote the hydrolysis of particulates, which is considered as a rate‐limiting step. This study investigated the effects of enzymatic pretreatment on hydrolytic solubilization of food waste with commercial enzyme. Both acidification efficiency and volatile fatty acid (VFA) production potential of enzymatically pretreated food waste were examined under controlled laboratory conditions. Experimental results indicated that protease exhibited the highest VSS reduction rate among three types of enzymes: carbohydrase, protease and lipase. A mixed enzyme treatment showed better reduction efficiency than a single enzyme treatment, and the highest volatile suspended solids (VSS) reduction was observed at an enzyme mixture ratio of 1:2:1 with carbohydrase:protease:lipase, respectively. It has been noted that pretreatment resulted in both maximum VFA production and the highest VFA content of soluble chemical oxygen demand at an enzyme mixture dosage of 0.1% (v/v). VFA production at this dosage revealed a 3.3 times higher rate than that of no‐enzyme added fermenter. The dominant VFAs were n‐butyrate followed by acetate. Copyright © 2006 Society of Chemical Industry     

Optimisation of steam pretreatment of SO2-impregnated mixed softwoods for ethanol production

Pretreatment of mixed softwoods with SO₂ impregnation and steam for production of ethanol has been investigated. The optimal conditions, both for sugar yield and ethanol yield, to assess the effect of inhibitors formed in the pretreatment, have been determined. The parameters investigated were: SO₂ concentration (1–6% (w/w) dry matter), temperature (190–230°C) and residence time (2–15 min). After pretreatment, the material was separated into a solid residue and a filtrate. The solid residue was enzymatically hydrolysed with 2% dry matter (w/w). To investigate fermentability, the hydrolysed filtrate was fermented using Saccharomyces cerevisiae. The effects of the different parameters are described by response-surface modelling. The highest experimental sugar yield of 42·1 g per 100 g dry matter was obtained at 210°C and 5·5 min residence time. Although the fermentabilities were good for all filtrates with yields greater than 90% of the yield obtained in a pure glucose reference solution, the pretreatment has a clear influence on the ethanol production rate. © 1998 SCI     

盐酸-乙二醇-水介质高效预处理山核桃壳及其糖化工艺

为了提高木质纤维素的酶解效率,采用盐酸辅助乙二醇对山核桃壳进行预处理。通过油浴的处理方式优化得出的最佳预处理条件为:处理介质为盐酸-乙二醇-水(1.2%:88.8%:10%,质量分数)的混合物,预处理温度为130℃,预处理时间为30min。为了减小预处理的温度和时间,采用微波辐射的辅助预处理,最佳预处理条件为:微波辐射温度100℃,微波辐射时间5min,微波辐射功率200W。糖化预处理后的山核桃壳经水解72h后,其还原糖产率可达到88.6%(油浴)和74.2%(微波)。利用电镜(SEM)和红外光谱(FT-IR)分析油浴和微波预处理后的山核桃壳,可以发现山核桃壳紧密的结构遭到破坏,变成更加易于酶解的松散、多孔结构,增加了酶可及度,因此很大程度上提高了糖化率。可见,盐酸-乙二醇-水溶液高效预处理可以提高山核桃壳酶解糖化的效率。