酸/碱性低共熔溶剂预处理对轻木物化性质及酶水解影响

采用酸/碱性低共熔溶剂（DES）在110 ℃和5 h下预处理轻木原料,分析了预处理前后轻木的化学组成、表面形貌、结构变化和酶水解性能。结果表明,3种酸/碱性DES预处理均可有效解构轻木原料。酸性DES可去除几乎所有的半纤维素和部分木质素,且酸性较强的氯化铝六水合物/丙三醇体系处理导致部分纤维素降解。碱性氯化胆碱/乙醇胺体系预处理后木质素大量去除,残留物中保留大量碳水化合物。预处理可显著增效纤维素酶水解,葡萄糖得率由原料的16.5%提升至52.6%~60.7%。DES经循环使用3次后纤维素酶解效率仍可达原料的2.5倍以上。     

硬毛粗盖孔菌预处理对玉米秸秆酶水解及组分变化的影响

以硬毛粗盖孔菌（Funalia trogii）为研究对象,比较其在不同预处理时间的产酶特征、预处理前后玉米秸秆酶解产糖量及其组分变化。结果表明,硬毛粗盖孔菌对木质素的降解以漆酶和锰过氧化物酶的协同作用为主导,漆酶和锰过氧化物酶活最高分别为341 IU/g和33 IU/g。经生物预处理14 d后的玉米秸秆酶解产糖量可达到350.74 mg/g秸秆,较原料提升184%。玉米秸秆组分的变化与其酶解增效密切相关,F. trogii预处理14 d后木质素和半纤维素含量分别降低了33.99%和36.61%,而纤维素仅降解8.77%,木质素和半纤维素的选择性降解,可显著降低玉米秸秆酶解抗性屏障,提升其酶解糖化效率。硬毛粗盖孔菌预处理玉米秸秆可实现木质纤维素的高效转化,缩短预处理时间,降低处理成本。     

基于乙醇胺的深度共熔溶剂预处理小麦秸秆提高其多糖酶解效率

为了探索基于乙醇胺的深度共熔溶剂预处理生物质的作用机制,本研究以氯化胆碱为氢键受体(HBA),以乙醇胺的化合物为氢键供体(HBD),合成了7种DES对其理化特性进行了测定,对比研究不同DES对小麦秸秆组分和酶解效率的影响。结果表明:30℃下,DES的粘度介于0.04～1.37 Pa·s,导电率0.29～3.57 ms/cm,5 mM DES的pH值介于7.41～11.02;90℃下对木质素和木聚糖的溶解度高达425 mg/g和523 mg/g,而对纤维素几乎不溶;经这些DES预处理后,小麦秸秆中的多糖酶解效率得到了显著提高,并且DES的预处理效果依赖于p H值,其中[氯化胆碱]:[乙二胺]为最适小麦秸秆预处理溶剂,90℃下预处理4h后木质素去除率83.14%,还原糖收率为93.88%。该类DES可选择性地从小麦秸秆中除去大量木质素和部分木聚糖,而未改变纤维素的晶体结构,从而提高后续酶解效率显著,并发现该类DES对禾本科类生物质和桉木有良好的预处理效果,预处理后糖收率明显提高(57.10%～98.13%),但对松木效果不佳。本研究可为用于生物质预处理的新型DES的合理设计提供一定的理论参考。     

离子液体预处理对玉米秸秆酶解效率的影响

离子液体作为一种可应用于木质纤维素预处理的新型绿色溶剂,以其处理效率高、环境友好等优势越来越受到人们的关注。采用4种离子液体:1-乙基-3-甲基咪唑醋酸盐([Emim]Ac)、1-烯丙基-3-甲基咪唑氯盐([Amim]Cl)、1-丁基-3-甲基咪唑硫酸氢盐([Bmim]HSO4)、1-丁基-3-甲基咪唑四氟硼酸盐([Bmim]BF_4),处理玉米秸秆,比较预处理后物料的酶解效果,并考察预处理后秸秆的成分、表面形态和结构的变化对酶解效率的影响,以探究离子液体预处理提高酶解效率的机制。结果表明,[Emim]Ac、[Amim]Cl、[Bmim]BF_4等3种离子液体在130℃下处理玉米秸秆1.5 h均可以在一定程度上去除木质素,有效地打破木质素与半纤维素的连接键,提高酶解效率。其中,[Emim]Ac具有较好的木质素选择性脱除效果,使木质素去除率达54.47%,有效破坏了包裹着纤维素的致密网状结构,增加物料的表面粗糙度,同时使纤维素由晶型I转变为更易酶解的晶型II,使预处理后秸秆的酶解效率提高到91.20%,是预处理前酶解效率的4.77倍。     

对甲基苯磺酸预处理玉米秸秆动力学及酶解特性研究

本研究采用对甲基苯磺酸（p-TsOH）预处理玉米秸秆,研究了3个预处理因素（p-TsOH质量分数、水解温度和水解时间）对其三大组分分离的影响。通过两相模型,得到木质素和半纤维素脱除动力学模型,并探究了处理后残渣的酶解性能。结果表明,p-TsOH预处理玉米秸秆在温和条件下即可快速溶出木质素和半纤维素,而对纤维素的降解较小;木质素脱除反应和半纤维素脱除反应的表观活化能分别为66.5 kJ/mol和50.5 kJ/mol;预处理后,木质纤维的顽抗结构被破坏,表面木质素含量降低,p-TsOH预处理可以有效提高原料的酶解得率;在p-TsOH质量分数为50%、水解温度为95℃和水解时间为40 min条件预处理后,残渣酶解得率为72.9%。     

全生物基三元DES预处理促进芦竹酶解机理研究

针对二元中性低共熔溶剂（DES）体系效率低的问题,构建新型全生物基三元DES（氯化胆碱/乙酰丙酸/1,4-丁二醇）体系,并用于芦竹（Arundo donax L.）预处理;采用成分分析、扫描电子显微镜（SEM）、X射线衍射仪（XRD）、傅里叶变换红外光谱仪（FT-IR）对预处理前后芦竹化学成分、结构及表面形貌变化等进行分析,结合复合动力学模型探究预处理促进芦竹酶解机理。结果表明,三元DES是高效的预处理体系,在140 ℃下处理3 h后,木质素和半纤维素的脱除率分别达46.4%和75.6%,残渣纤维素和聚木糖酶解率高达~100%和96.6%;建立的复合动力学模型可准确地描述三元DES预处理耦合酶解过程中葡萄糖和木糖变化行为（R² > 0.99）。由预处理温度升高引起的半纤维素和木质素高效脱除、纤维表面粗糙度增大及纤维素结晶结构破坏是促进芦竹酶解的主要原因。     

氨化预处理对玉米秸秆酶解产糖的影响

为综合利用玉米秸秆,加快纤维素酶降解玉米秸秆。本文以玉米秸秆为原料,还原糖产量为主要指标,通过氨化预处理后酶解玉米秸秆,采用DNS法测定还原糖产量,并考察氨化剂种类、浓度、固含量和氨化时间对玉米秸秆酶解产糖的影响。结果表明,在以碳酸铵为氨化剂,氨化剂浓度为20%,固含量为50%,氨化时间为11 d,在此条件下,还原糖产量最高为314.18 mg/mL,与直接酶解秸秆相比提高51.80%。扫描电镜结果显示,米秸秆经碳酸铵氨化预处理后,木质素和纤维素的结构发生变化,表面结构变得粗糙疏松,纤维素暴露,更有利于纤维素酶的作用。此外,FTIR发现,氨化处理后玉米秸秆在2920和1650 cm^-1处的吸收峰减弱,其峰值降低一定程度上代表木质素结构被破坏。总体来看,玉米秸秆经过碳酸铵氨化预处理后,更有利于酶解玉米秸秆。     

Box-Behnken法优化玉米秸秆预处理工艺对酶解糖化的影响

为促进生物炼制产业发展,提高玉米秸秆酶解糖化效率,运用Box-Behnken试验设计优化预处理工艺,研究硫酸质量分数、反应时间、反应温度和固液比四个因素对半纤维素水解率的影响规律,并结合扫描电子显微镜、红外光谱仪、X-射线衍射仪分析玉米秸秆微观形貌、结构等指标。结果表明：玉米秸秆预处理最佳工艺为反应温度100℃、硫酸质量分数1.2%、反应时间120 min、固液比1∶9（g∶mL）,在此条件下半纤维素水解率为84.93%,木质素脱除率为46.15%,预处理水解液还原糖质量浓度为2.04 g/100mL,木糖产率为74.22%,87.89%纤维素保留在固体部分,经72 h酶解反应酶解率达到85.79%,未处理玉米秸秆酶解率仅为32.25%。     

酸性低共熔溶剂预处理制备含木质素的纤维素纳米纤丝及其复合膜的研究

采用酸性低共熔溶剂（deep eutectic solvent,DES）预处理并结合高压均质法制备了含木质素的纤维素纳米纤丝（lignin-containing cellulose nanofibril,LCNF）,并与聚乙烯醇（PVA）共混制备了LCNF/PVA复合膜,探讨了2种酸性DES预处理的效果,分析比较了LCNF的特性及LCNF/PVA复合膜的性能。结果表明,乳酸-氯化胆碱（LC）和乙酸-氯化胆碱（AC）对半纤维素的提取率均达到78%以上,其中LC预处理后用乙醇洗涤的处理方式对木质素的提取率高达61.2%;DES预处理后,乙醇洗涤有利于木质素的分离;利用LC制备的纤维素纳米纤丝（LC-E-LCNF）的直径为50～100 nm;相较于纯PVA膜,LCNF/PVA复合膜的疏水性明显提高,应力提升至70.3 MPa,紫外屏蔽性接近100%,且具有良好的热稳定性和雾度,以及一定的保鲜性能,该复合膜有望应用于食品包装领域。     

不同类型深度共熔溶剂预处理的甘蔗渣酶解效率差异

为了探索深度共熔溶剂(DES)预处理生物质的机制,本文分别设计了五种以氯化胆碱为氢键受体(HBA)和以苹果酸为氢键供体(HBD)的DESs来预处理甘蔗渣,分析HBD和HBA对甘蔗渣组分和酶解效率的影响。在氯化胆碱为HBA的DESs中,乳酸-氯化胆碱(LC)的预处理效果和酶解效率最好,所得甘蔗渣残渣的纤维素含量为72.92%,纤维素降解度为60.43%,葡萄糖收率为56.90%;而在苹果酸为HBD的DESs中,苹果酸-氯化胆碱的预处理效果最佳,木聚糖和木质素去除率均为最高,纤维素降解度为43.35%,葡萄糖收率为38.00%。研究结果证明DES的HBA和HBD的作用皆不可忽略,其分子间氢键作用强度与其对生物质的解构能力负相关。并发现甘蔗渣的木聚糖去除率与氢键受供体的p Ka值具有一定的相关性;纤维素降解度与木聚糖去除率正相关,而与木质素去除率无关。此外,在一定范围内,DES分子间的氢键作用强度、DES与甘蔗渣的氢键缔合作用与预处理温度和时间有相关性。本研究为用于生物质预处理的新型DES的设计提供了一定的理论参考。     

改进玉米秸秆化学预处理提高后续生物酶解糖化效率的研究

采用NaOH、NaOH+AQ、NaOH+Na2SO3、H2SO4+Na2SO3、NaOH+Na2S以及H2SO4预处理玉米秸秆,通过改变最高温度和药品用量考察了不同处理方式对酶解效率及总糖得率的影响。结果表明:在相同处理条件下,采用NaOH+Na2SO3预处理有利于提高后续的酶解效率及总糖得率。在140℃及10%用碱量时,碱性亚硫酸钠法的处理效果最佳,聚葡萄糖和聚木糖的酶解效率分别达到84.7%和81.1%。基于初始原料的总糖得率约为0.44g/g初始秸秆,相比同样条件的单一NaOH预处理提高了13.5%。     

木质纤维素类生物质生物预处理菌种筛选

以生物质的转化率(TR)、糖化率(SR)为评价标准,在竹粉、稻草和玉米秸秆3种生物质上筛选了33株采自神农架自然保护区的白腐菌菌株,发现针对不同生物质,适用于生物预处理的菌株不同:竹粉基质为杂色云芝,稻草基质为侧耳属菌株,玉米秸秆基质为乳白耙菌。所筛出白腐菌预处理时间显著缩短,以相应菌株处理竹粉、稻草和玉米秸秆15d,其生物质TR分别提高25.8%、47.0%和136.3%,SR依次达到14.1%、39.4%和37.5%。3种生物质中木质素含量与其糖化率关系密切。     

Biotreatment of Wastewater from Soda-pretreatment Process of Corn Stover Using White-rot Fungus Z-6

Alkaline pretreatment of straw materials prior to enzyme hydrolysis is a key step for bioconversion of lignocellulose to bioethanol and chemicals. Wastewater from the alkaline pretreatment process must be treated before discharge to minimize its environmental impact. In this study, biotreatment of the wastewater from soda-pretreatment process of corn stover was investigated using fungus Z-6, and some indexes such as color, chemical oxygen demand (COD), and lignin content of wastewater before and after biotreatment were determined to assess the effect of the biotreatment. Results showed that fungus treatment could remove color up to approximately 72% after 2 d, and decrease COD and lignin content by about 63% and 60%, respectively after 3 d. The wastewater was fractionated using dynamic ultrafiltration method, and the changes in lignin contents of the effluent fractions with different molecular weights before and after biotreatment were analyzed. Some compounds produced by the fungus during treatment were identified using gas chromatography-mass (GC-MS) spectrometer, which revealed that depolymerization of lignin occurred during the biotreatment process.     

玉米秸秆木质素的提取工艺优化及表征

应用碱溶-醇沉-酸析方法提取玉米秸秆木质素,Box-Behnken试验优化工艺条件为NaOH溶液浓度2.40 mol/L、反应时间3.10 h、提取温度74 ℃,木质素的提取率达到69.71%。经热重、傅里叶变换红外光谱和紫外-可见吸收光谱结构分析表明,木质素在130～500 ℃内发生热分解反应,部分官能团发生交联后具有很高的热稳定性,最大紫外吸收峰位于282 nm波长处,存在较多的化学活性基团。所得木质素因其化学活性高,可通过分子设计改性形成高分子材料,从而为玉米秸秆的资源化利用提供新途径。     

不同预处理方式对玉米秸秆酶解液成分的影响

玉米秸秆中的单糖或者寡糖的释放由于芳香族聚合物木质素阻遏纤维素酶进行糖解聚作用而效率地下.然而预处理作用可以有效地移除木质素或者打破木质素的结构,从而可以增强还原糖的释放.其过程主要包括2个生物转化程序:玉米秸秆中纤维素的水解产生还原糖,然后进行生物乙醇发酵生产过程.在该研究中,通过HPLC方法监测不同预处理方法处理玉米秸秆酶水解液中的成分,从而得到最佳的预处理方法.结果表明,磁力搅拌辅助CO2激光协同通气预处理方法的糖化效果高于其他预处理方法.     

Comprehensive Evaluation and Prediction of the Effectiveness of H2O2-assisted Na2CO3 Pretreatment of Corn Stover Using Multivariate Analysis

In this study, multivariate analysis methods, including a principal component analysis (PCA) and partial least square (PLS) analysis, were applied to reveal the inner relationship of the key variables in the process of H₂O₂-assisted Na₂CO₃ (HSC) pretreatment of corn stover. A total of 120 pretreatment experiments were implemented at the lab scale under different conditions by varying the particle size of the corn stover and process variables. The results showed that the Na₂CO₃ dosage and pretreatment temperature had a strong influence on lignin removal, whereas pulp refining instrument (PFI) refining and Na₂CO₃ dosage played positive roles in the final total sugar yield. Furthermore, it was found that pretreatment conditions had a more significant impact on the amelioration of pretreatment effectiveness compared with the properties of raw corn stover. In addition, a prediction of the effectiveness of the corn stover HSC pretreatment based on a PLS analysis was conducted for the first time, and the test results of the predictability based on additional pretreatment experiments proved that the developed PLS model achieved a good predictive performance (particularly for the final total sugar yield), indicating that the developed PLS model can be used to predict the effectiveness of HSC pretreatment. Therefore, multivariate analysis can be potentially used to monitor and control the pretreatment process in future large-scale biorefinery applications.     

Technical note: A comparison of alkali treatment methods to improve neutral detergent fiber digestibility of corn stover

The objective of this study was to compare neutral detergent fiber (NDF) digestibility of corn stover that had been treated by 2 alkali treatment methods. Two experiments were conducted to test a sodium hydroxide (NaOH) treatment method that uses an ethanol/water co-solvent (NaOH/ethanol-H₂O, United States Patent No. 20140220228) and a calcium hydroxide (CaOH) treatment method, which uses water as a solvent (CaOH/H₂O). An in situ trial was conducted to compare NDF digestion kinetics between NaOH/ethanol-H₂O-treated stover, CaOH/H₂O-treated stover, untreated corn stover, and soy hulls. The digestion rate of potentially digestible NDF (k_d) of NaOH/ethanol-H₂O-treated corn stover (5.36%/h) was higher than CaOH/H₂O-treated stover (2.27%/h), or untreated corn stover (1.76%/h) and similar to the k_d of soy hulls (4.93%/h). The indigestible NDF (iNDF) fraction of untreated corn stover (35.1% of NDF) was reduced by CaOH/H₂O treatment (27.3% of NDF) and by NaOH/ethanol-H₂O treatment (2.8% of NDF). The iNDF fraction in soy hulls (3.6% of NDF) was similar to iNDF of NaOH/ethanol-H₂O-treated stover. An in vivo digestibility trial was also conducted to compare fiber digestibility of diets supplemented with untreated corn stover, NaOH/ethanol-H₂O-treated corn stover, or soy hulls. Total-tract apparent dry matter (DM) and NDF digestibility were measured with 8 lactating Holstein cows in a replicated 4 × 4 Latin square with four 21-d periods. Apparent DM digestibility (DMD) was improved when supplemental soy hulls were added to the base diet (60.0% DMD) compared with the base diet with no supplemental fiber (57.7% DMD). Apparent DM digestibility was reduced when diets were supplemented with untreated stover (52.4%). Dry matter digestibility of NaOH/ethanol-H₂O-treated stover was similar (54.8% DMD) to all other treatments. Digestibility of NDF was lowest when cows were fed the diet with supplemented untreated stover (35.5% of NDF), and improved when soy hulls (40.6% of NDF) or NaOH/ethanol-H₂O-treated stover (43.8% of NDF) were added to the diets. The NaOH/ethanol-H₂O treatment process improves the DM and NDF digestibility of corn stover to values similar to those of soy hulls.