卧式酶解罐用于预处理玉米秸秆水解研究

利用卧式滚筒酶解罐、立式搅拌酶解罐和卧式搅拌酶解罐分别对预处理玉米秸秆(PCS)进行水解研究,分析了酶解过程中p H、密度、总固体(TS)含量、纤维素含量(TC)、不可溶性总固体含量(FIS)、葡萄糖含量和木糖含量的变化趋势。卧式滚筒酶解罐用于TS含量较高的PCS酶解时,反应物容易粘附在反应桶内壁,不利于酶解有效地进行,138 h水解产生的葡萄糖含量为8.6%,低于立式搅拌酶解罐120 h水解产生的葡萄糖含量11.4%。而卧式搅拌酶解罐用于TS含量(25%)较高的PCS酶解时,120 h水解产生的葡萄糖含量为7.43%,比相同TS含量的立式搅拌酶解罐中葡萄糖含量高出0.26%。研究表明,3种酶解罐中,卧式搅拌罐更适合用于PCS的酶解。采用卧式搅拌酶解与同步糖化发酵耦合过程,TS含量为25%条件下,发酵液中乙醇含量可达到3.58%,纤维素水解率为76.8%。     

超声波辅助碱法预处理提高蔗渣酶解糖化活性的研究

采用超声波对蔗渣碱预处理过程进行强化,研究其对蔗渣酶解糖化活性的影响,并通过成分分析、FTIR、XRD、SEM对比了处理前后蔗渣组成、形态结构和结晶性能的变化情况,探讨了超声波强化作用的机理.研究结果表明,采用超声波辅助处理可使碱预处理温度明显降低,蔗渣酶解糖化活性明显提高,酶解总糖产率比单一碱处理提高了59.6%.蔗渣成分分析表明,采用超声波可以去除更多的木质素;FTIR及XRD分析表明,超声波的强化作用使处理后的蔗渣结构发生了变化,其分子问氢键作用变弱、结品度有所降低;SEM分析表明,经超声波处理后的蔗渣纤维表面结构发生了更明显的变化,表面出现凹坑、裂纹和小孔,结构变得松散.     

碱性胍预处理水稻秸秆研究

以水稻秸秆为研究对象,采用有机强碱——胍进行预处理,考察了催化剂用量、预处理时间和温度对预处理效果的影响。以扫描电镜(SEM)、X-射线衍射仪(XRD)、红外光谱仪(FTIR)、热重分析仪(TG)对预处理前后样品进行了表征。结果表明:胍用量为3%、温度为60℃、时间为6 h是较适宜的预处理条件,催化剂用量是预处理水稻秸秆最关键的因素。SEM照片显示,预处理后秸秆表面呈现不规则的层片状皱褶、裂缝和孔洞;XRD表征显示,预处理后纤维素结晶度均提高;FTIR表征显示,胍对去除木质素和降解氢键作用明显;TG表征表明预处理前后水稻秸秆具有不同的热稳定特性。     

NaOH/H2O2预处理促进玉米秸秆酶解产糖工艺条件的研究

采用正交实验初步探讨了NaOH/HO2O2对经白腐菌Hyrophous sp.254处理15 d的玉米秸秆进行预处理的最佳条件.在NaOH/H2O2预处理过程中,NaOH浓度、H2O2体积分数、底物浓度及预处理时间均对秸秆的纤维素酶酶解效率存在一定影响.试验表明,NaOH/H2O2的最佳预处理条件:NaOH浓度为7g/L,H2O2体积分数为0.7%,底物浓度为50g/L,处理时间为24h.在优化的工艺条件下,玉米秸秆的还原糖产量达到了0.417 g/g,H2O2用量减少了30%,废水排放量减少了60%.     

碱性双氧水预处理玉米秸秆性质研究

使用碱性双氧水对玉米秸秆进行预处理,可以有效提高秸秆的酶解效果。实验表明,最优预处理参数为使用分别占秸秆质量16%的 H₂O₂和25.6% 的NaOH,于40℃下预处理秸秆24 h。对经不同预处理剂处理后的秸秆进行酶解,发现NaOH及碱性双氧水预处理秸秆的酶解还原糖产量为7.48 g/L和8.26 g/L,而经H₂O及H₂O₂预处理秸秆的还原糖产量仅为1.35 g/L和1.59 g/L。通过木质纤维素含量及SEM分析发现,氢氧化钠主要作用为溶解秸秆中的木质素及半纤维素,而双氧水的存在则会破坏秸秆表面结构。计算秸秆预处理前后质量损失发现,双氧水的存在不能显著提高秸秆预处理后的质量损失,但会氧化分解被氢氧化钠溶解的大分子物质,对此过程机理及产物还需进行深入的研究。     

碱和双氧水预处理玉米秸秆的试验研究

研究了在5%NaOH中加入不同质量分数的双氧水时,对玉米秸秆的预处理效果;在预处理后的玉米秸秆中加入纤维素酶,考察此时酶解还原糖得率随预处理程度的变化;对浸泡时间、双氧水浓度、固液比3个因素进行单因素试验。试验结果表明,质量分数为2.5%的浓度下,糖得率最大;在2.5%H2O2浸泡24 h,固液比对酶解糖化几乎没有影响;当浸泡时间为24,72,96 h时,糖得率相差甚微。设计正交试验对预处理的条件进行优化,分析预处理玉米秸秆的各因素,以木质素去除率为基准参数,得到水解木质纤维素的适宜预处理条件:5%NaOH下加入质量分数为2.5%的双氧水,浸泡时间为72 h,固液比为1∶20。预处理后木质素的去除率为61.52%;加入纤维素酶酶解,还原糖得率为39.30%。     

蒸汽爆破预处理玉米芯及其酶解工艺研究

以蒸汽爆破预处理后的玉米芯为原料,进行了玉米芯酶解工艺条件的研究。粉碎后的玉米芯在压力2.8 MPa、保压时间240 s条件下蒸汽爆破预处理,在初始固形物含量为14%(w/v),pH 5.0的条件下,分别添加纤维素酶15 FPA/g(底物)、木聚糖酶225 IU/g(底物),同时添加环境因子MgSO40.005 g/g(底物)、Tween-800.001 g/g(底物),糖化48 h后,还原糖浓度达到71.81 g/L,糖化率达到80.85%。试验结果表明,蒸汽爆破预处理及添加适量环境因子对玉米芯的糖化效果影响显著。     

蒸汽爆破预处理中影响酶解效果因素的研究

为提高秸秆蒸汽爆破预处理制乙醇的酶解率及经济效益,研究了蒸汽爆破预处理过程中影响酶解效果的物料温度、喷爆出口直径、汽爆次数等因素,以寻找提高酶解效率的方法。试验结果显示,物料温度对酶解效果有显著影响,在不破坏纤维素结构且不产生酶解抑制物的前提下,温度越高越有利于水解;在不致堵塞喷爆口的前提下,喷爆出口直径越小酶解效果越好;汽爆次数对于酶解物料预处理效果有着显著的积极影响。     

稻草秸秆辐照酶解工艺优化

通过采用60Co-γ辐照处理稻草秸秆,提高稻草秸秆的酶解效果。采用离子色谱仪测定稻草秸秆酶解液中可发酵性糖的含量,对水解温度、加酶量、液固比、水解时间4个因素进行单因素试验分析,对稻草秸秆酶解条件进行优化,建立稻草秸秆辐照酶解新工艺。研究结果表明,稻草秸秆辐照剂量在0～2 000 kGy内,辐照预处理最佳剂量为1 200 kGy;得到稻草秸秆最优辐照酶解条件:预处理辐照剂量为1 200 kGy、水解温度为45℃、水解时间为36 h、液固比为60、加酶量为120 U/g。在此最佳条件下,稻草秸秆纤维素、半纤维素总转化率达71%。     

超声波辅助离子液体预处理的纤维素酶解糖化

利用超声波辅助离子液体1-烯丙基-3-甲基咪唑甲酸盐([Amim][COOH])对纤维素进行预处理,并测定聚合度变化和酶解速率。试验表明,再生纤维素的聚合度有明显下降;酶解速率随预处理温度的增加呈现先增加后下降的趋势,在90℃出现最大值;在外加超声波条件下,经离子液体预处理的纤维素酶解初速度可达11.10g/(L·h),相比未处理的纤维素,酶解速度提高33%。通过电子显微镜和红外光谱分析,再生纤维素出现了解聚现象,结晶度也明显下降。     

Optimizing thermomechanical pretreatment conditions to enhance enzymatic hydrolysis of wheat straw by response surface methodology

Wheat straw was pretreated with a thermomechanical process developed in our laboratory to improve the enzymatic hydrolysis extent of potentially fermentable sugars. This process involves subjecting the lignocellulosic biomass for a short time to saturated steam pressure, followed by an instantaneous decompression to vacuum at 5 kPa. Increasing of the heat induced by saturated steam result in intensive vapour formation in the capillary porous structure of the plant material and the subsequent release of the pressure to vacuum allows fixing the expanded structure. Response surface methodology (RSM) based on central composite design was used to optimize three independent variables of the pretreatment process: processing pressure (300-700 kPa), initial moisture contents of wheat straw (10-40%) and processing time (3-62 min). The process was optimised for hydrolysis yield and initial hydrolysis rate obtained by enzymatic hydrolysis on the pretreated solids by Celluclast (1.5 L). The analysis of variance (ANOVA) revealed that, among the process variables, processing pressure and processing time have the most significant effect on the hydrolysis yield and on initial rate of hydrolysis whereas initial moisture content observed significantly lower effect on the two responses. The predicted hydrolysis yield and in a lesser extent the predicted initial rate of hydrolysis agreed satisfactorily with the experimental values with R² of 96% and 86% respectively.     

稀酸处理对秸秆厌氧发酵产氢的影响

以稻草秸秆为纤维素原料,先利用稀硫酸对其进行预处理,再利用活性污泥进行厌氧发酵产氢。试验研究了压力、温度、硫酸浓度、加压时间、固液比以及原料粒度对预处理结果的影响,并根据产氢量优化了预处理条件。试验结果表明:在硫酸浓度为0.7%、处理压力为0.1MPa、加压时间为60min、固液比为1∶12,秸秆原料过60目筛的情况下预处理效果最好,此时每克秸秆产氢量为113ml,秸秆中半纤维素、纤维素的利用率为87.47%,秸秆的有效利用率为52.38%。     

Insights into biological delignification of rice straw by Trametes hirsuta and Myrothecium roridum and comparison of saccharification yields with dilute acid pretreatment

Rice straw is the most abundant agricultural residue on a global scale and is widely available as feedstock for cellulosic fuel production. However, it is highly recalcitrant to biochemical deconstruction and also generates inhibitors that affect enzymatic saccharification. Rice straw from eastern Arkansas was subjected to dilute acid pretreatment (160 °C, 48 min and 1.0% sulfuric acid) and solid-state fermentation with two lignocellulolytic fungi, Trametes hirsuta and Myrothecium roridum, and their saccharification efficacies were compared. T. hirsuta and M. roridum were tested separately; pretreatment of rice straw with either strain for seven days resulted in 19 and 70% enrichment of its holocellulose content, respectively. However, liquid chromatography analysis of the alkali extracts showed significant differences in cell wall degradation by T. hirsuta and M. roridum. T. hirsuta removed 15% more phenolic compounds and 38% more glucan than M. roridum, while M. roridum removed 77% more xylan than T. hirsuta. Fungal and dilute acid pretreated biomass was then hydrolyzed using Accellerase^® 1500, a saccharification cocktail. Saccharification efficiency of M. roridum was 37% higher than that of dilute acid pretreatment of rice straw, requiring 8% lower enzyme loading and 50% shorter enzymatic hydrolysis duration. Alkali extraction of fungal pretreated biomass also yielded 10–15 g kg⁻¹ of acid precipitable polymeric lignin (APPL), which is a valuable co-product for biorefineries. In comparison to dilute acid pretreatment, fungal pretreatment could be a cost-effective alternative for the degradation of recalcitrant biomass, such as rice straw.     

Optimisation of dilute alkaline pretreatment for enzymatic saccharification of wheat straw

Physico-chemical pretreatment of lignocellulosic biomass is critical in removing substrate-specific barriers to cellulolytic enzyme attack. Alkaline pretreatment successfully delignifies biomass by disrupting the ester bonds cross-linking lignin and xylan, resulting in cellulose and hemicellulose enriched fractions. Here we report the use of dilute alkaline (NaOH) pretreatment followed by enzyme saccharifications of wheat straw to produce fermentable sugars. Specifically, we have assessed the impacts of varying pretreatment parameters (temperature, time and alkalinity) on enzymatic digestion of residual solid materials. Following pretreatment, recoverable solids and lignin contents were found to be inversely proportional to the severity of the pretreatment process. Elevating temperature and alkaline strengths maximised hemicellulose and lignin solubilisation and enhanced enzymatic saccharifications. Pretreating wheat straw with 2% NaOH for 30 min at 121 °C improved enzyme saccharification 6.3-fold when compared to control samples. Similarly, a 4.9-fold increase in total sugar yields from samples treated with 2% NaOH at 60 °C for 90min, confirmed the importance of alkali inclusion. A combination of three commercial enzyme preparations (cellulase, ??-glucosidase and xylanase) was found to maximise monomeric sugar release, particularly for substrates with higher xylan contents. In essence, the combined enzyme activities increased total sugar release 1.65-fold and effectively reduced cellulase enzyme loadings 3-fold. Prehydrolysate liquors contained 4-fold more total phenolics compared to enzyme saccharification mixtures. Harsher pretreatment conditions provide saccharified hydrolysates with reduced phenolic content and greater fermentation potential.     

小麦秸秆转化为可发酵糖的研究

对小麦秸秆水解转化为可发酵糖进行了研究，考察了小麦秸秆预处理方法以及温度、pH值、酶用量、底物浓度和反应时间等因素对小麦秸秆酶水解的影响。试验结果表明，汽蒸加蒽醌方法是较好的预处理方法。酶解最佳工艺为：温度48℃，pH值5．2，酶解时间24h，酶用量与底物的最佳配比0．160：1；底物浓度≥1％，以1．5％～2．5％为宜，此时还原糖得率达32．4％。     

机械活化预处理对蔗渣酶解产糖影响的研究

采用机械活化方法对蔗渣进行预处理,研究其对蔗渣酶解产糖的影响。用红外光谱、X-射线衍射和扫描电镜测定预处理前后蔗渣结构及表面形态的变化,并分析其作用机理。研究结果表明,机械活化用于蔗渣预处理,可明显提高预处理后蔗渣的酶解产糖率。酶解时间为48 h时,蔗渣酶解产糖率从未处理时的19.86%提高到59.34%。蔗渣酶解产糖率的提高是由于机械活化处理使得蔗渣纤维素分子间部分氢键发生断裂、结晶度下降、表面有序结构被破坏的所致。     

Microwave-assisted alkali pretreatment of rice straw to promote enzymatic hydrolysis and hydrogen production in dark- and photo-fermentation

Rice straw was pretreated by microwave-assisted alkali to improve saccharification in enzymatic hydrolysis and hydrogen yield in combined dark- and photo-fermentation in this paper. A maximum reducing sugar yield of 69.3 g/100 g TVS was obtained when 50 g/l rice straw was pretreated by microwave heating for 15 min at 140 °C in 0.5% NaOH solution and then enzymatically hydrolyzed for 96 h. When hydrolyzed rice straw was used for hydrogen production by anaerobic bacteria in dark-fermentation, a maximum hydrogen yield of 155 ml/g TVS was obtained. The residual solution (mainly acetate and butyrate) from dark-fermentation was reutilized for hydrogen production by immobilized photosynthetic bacteria in photo-fermentation. By combination of dark- and photo-fermentation, the maximum hydrogen yield was greatly enhanced to 463 ml/g TVS, which is 43.2% of the theoretical hydrogen yield.     

稻草秸秆多酶水解条件研究

研究了稻草秸秆经过稀酸预处理后的酶水解条件,得到用于生产燃料乙醇的还原糖。试验结果表明:稻草秸秆经1%(w/w)的稀硫酸浸润,液固比(v/w)为5∶1,在121℃条件下处理60min后,每克稻草秸秆的初始水解还原糖得率达到0.187g。预处理后,在45℃,pH4.8,120r/min,48h条件下,采用酶的添加量最优配比(每克秸秆添加木聚糖酶217IU,纤维素酶5.13FPU,果胶酶25μ,β-葡聚糖酶500μ,淀粉酶150μ)时,水解产生的还原糖浓度达到最大值84.22g/L,原料水解率为41.19%。在酶水解糖化过程中,当MgSO4,Tween80的添加量分别为0.0001,0.005g时对纤维素酶有激活作用。