FED-BATCH SIMULTANEOUS SACCHARIFICATION AND FERMENTATION OF MICROWAVE/ACID/ALKALI/H2O2 PRETREATED RICE STRAW FOR PRODUCTION OF ETHANOL

The batch simultaneous saccharification and fermentation (SSF) of microwave/acid/alkali/H₂O₂ pretreated rice straw to ethanol was optimized using cellulase from Trichoderma reesei and Saccharomyces cerevisiae YC-097 cells prior to the fed-batch SSF studies. The batch SSF optima were 10% w/v substrate, 40°C, 15 mg cellulase/g substrate, initial pH 5.3, and 72 hours. Under the optimum conditions the ethanol concentration and its yield were 29.1 g/L and 61.3% respectively. Based on the optimal batch SSF, the fed-batch SSF was investigated and its operation parameters were optimized. Under its optimal conditions the ethanol concentration reached 57.3 g/L, while its productivity and yield were only slightly less than those in the batch SSF. This suggests that fed-batch SSF is a potential operation mode for effective ethanol production from microwave/acid/alkali/H₂O₂ pretreated rice straw.     

绿液预处理玉米秸秆产纤维素酶的研究

研究了绿液预处理玉米秸秆对里氏木霉产纤维素酶的影响。通过正交试验考察3个预处理条件对玉米秸秆产纤维素酶的影响,从极差和方差分析可知,对绿液预处理玉米秸秆产纤维素酶的影响程度由大到小依次是总碱量、蒸煮温度、硫化度,最大滤纸酶活(FPA)达到2.6 IU/mL。比较在蒸煮温度140 ℃和170 ℃,总碱量4 %,硫化度0、20 %、30 % 与40 %下所产的FPA,经综合评定,在最优条件下蒸煮温度140 ℃,总碱量4 %和硫化度0时可以尽量避免原料损失的前提下,保证FPA的大小,结果表明,里氏木霉利用绿液预处理玉米秸秆来产纤维素酶是可行的。以蒸煮温度140 ℃,总碱量4 %和硫化度0的条件下绿液预处理得到的玉米秸秆为碳源,碳源浓度为12 g/L,FPA和β-葡萄糖苷酶活(β-GA)分别达到2.5 IU/mL和1.3 IU/mL,产酶周期5 d。     

FED-BATCH SIMULTANEOUS SACCHARIFICATION AND FERMENTATION OF MICROWAVE/ACID/ALKALI/H2O2 PRETREATED RICE STRAW FOR PRODUCTION OF ETHANOL

The batch simultaneous saccharification and fermentation (SSF) of microwave/acid/alkali/H₂O₂ pretreated rice straw to ethanol was optimized using cellulase from Trichoderma reesei and Saccharomyces cerevisiae YC-097 cells prior to the fed-batch SSF studies. The batch SSF optima were 10% w/v substrate, 40°C, 15 mg cellulase/g substrate, initial pH 5.3, and 72 hours. Under the optimum conditions the ethanol concentration and its yield were 29.1 g/L and 61.3% respectively. Based on the optimal batch SSF, the fed-batch SSF was investigated and its operation parameters were optimized. Under its optimal conditions the ethanol concentration reached 57.3 g/L, while its productivity and yield were only slightly less than those in the batch SSF. This suggests that fed-batch SSF is a potential operation mode for effective ethanol production from microwave/acid/alkali/H₂O₂ pretreated rice straw.     

An approach to optimization of enzymatic hydrolysis from sugarcane bagasse based on organosolv pretreatment

BACKGROUND: The organosolv pretreatment followed by enzymatic hydrolysis of the pretreated material and subsequent fermentation of the hydrolysate produced, was the strategy used for ethanol production from sugarcane bagasse. The effect of different operational variables affecting the pretreatment (the catalyst type and its concentration, and the pretreatment time) and enzymatic hydrolysis stage (substrate concentration, cellulase loading, addition of xylanase and Tween 20, and the cellulase/β‐glucosidase ratio), were investigated. RESULTS: The best values of glucose concentration (28.8 g L^?1) and yield (25.1 g per 100 g dry matter) were obtained when the material was pretreated with 1.25% (w/w) H₂SO₄ for 60 min, and subsequently hydrolyzed using 10% (w/v) substrate concentration in a reaction medium supplemented with xylanase (300 UI g^?1) and Tween 20 (2.5% w/w). Fermentation of the broth obtained under these optimum conditions by Saccharomyces cerevisiae resulted in an ethanol yield of 92.8% based on the theoretical yield, after 24 h. CONCLUSION: Organosolv pretreatment of sugarcane bagasse under soft conditions, and subsequent enzymatic hydrolysis of the pretreated material with a cellulolytic system supplemented with xylanase and Tween 20, is a suitable procedure to obtain a glucose rich hydrolysate efficiently fermentable to ethanol by Sacharomyces cerevisiae yeasts. Copyright © 2010 Society of Chemical Industry     

超声波协同稀碱液处理稻草秸秆酶解糖化的研究

采用超声波与稀碱液联合预处理稻草秸秆,借助红外表征、X衍射和扫描电镜成像分析,对预处理稻草的结构组成以及酶解糖化进行了研究。结果表明:在超声场下的稀碱液能破坏稻草的秸秆结构,使更多的木质素被剥离,并由此提高秸秆的糖化率;与2%碱液处理相比,超声协同下的1%NaOH用量减少50%,纤维素损耗降低4%,稻草秸秆的糖化率达到27%(增加了7%),最终超声协同2%NaOH处理过的秸秆糖化率最高达30%。     

Enhanced biogas production from herbal‐extraction process residues by microwave‐assisted alkaline pretreatment

BACKGROUND: Lignocellulosic wastes such as herbal‐extraction process residues (HPR) are not easily utilized by microorganisms owing to their physical shielding of cellulose imparted by the non‐digestible lignin. Therefore, there is a great interest to develop an efficient pretreatment technique to disrupt recalcitrant structures of lignocellulosic wastes and improve renewable energy production. RESULTS: A microwave‐assisted alkaline pretreatment (MAP) method has been developed for the enhancement of biogas production from HPR. The maximum cumulative biogas production reached 1477 mL when the HPR was hydrolyzed by MAP for 30 min with an alkali loading of 0.12 g‐NaOH/g‐HPR, where the maximum weight loss of HPR after biogas fermentation reached 72.1%. CONCLUSION: The present work demonstrated that MAP is a promising method for improving bioconversion of lignocellulosic wastes to biogas. HPR pretreated by combining microwave irradiation and alkali resulted in releasing more soluble substances from HPR and increasing the accessibility of HPR for anaerobic biodigestion compared with traditional alkaline pretreatment (AP) and microwave‐assisted water pretreatment (MWP). Copyright © 2009 Society of Chemical Industry     

里氏木酶利用预处理小麦秆生产纤维素酶的应用研究

为了降低里氏木霉生产纤维素酶的成本,研究了小麦秸秆经白腐菌和酸处理后主要成分如纤维素、木聚糖、木质素含量的变化,采用正交实验考察了里氏木霉菌发酵小麦秆生产纤维素酶的最佳条件,研究得到的最佳条件为:小麦秆∶麸皮=2∶3,培养温度30℃,起始pH 5.0,发酵时间48 h。通过对正交实验条件的优化,发酵液滤纸酶活(FPA)为6.11 IU.mL-1,羧甲基纤维素酶活(CMCase)为29.11 IU.mL-1,纤维二糖酶活(CBA)为16.11 IU.mL-1。和原工艺相比FPA、CMCase和CBA分别提高了30.78%、26.82%和37.11%。     

Preparation of microcrystalline cellulose from rice straw under microwave irradiation

Crude cellulose was isolated from rice straw and then converted into microcrystalline cellulose (MCC) via partial hydrolysis. Both the isolation and partial hydrolysis were carried out under microwave. Rice straw was successively pretreated with alkaline and acid solutions before hydrolysis. Lignin and silica were almost removed but partial removal of hemicellulose in dilute alkali solution, and the residual hemicellulose was further removed in dilute acid solution. The total removal rates of hemicellulose, lignin and silica reached up 92.0%, 98.5%, and 96.8%, respectively. The cellulose content of 93.6 wt % in MCC was given by partial hydrolysis of crude cellulose isolated from rice straw. The comparison between microwave irradiation and traditional heating method was also investigated. Compared to traditional heating method, similar results were obtained while milder conditions, including shorter time and lower temperature, were required. An effective microwave‐assisted and energy‐efficient methodology using rice straw as the alternative source of cellulose fiber was developed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44901.     

Sugar recovery from rice straw by dilute acid pretreatment

Rice straw was pretreated with dilute sulfuric acid in order to decrease the amorphous portion and enhance enzyme accessibility. Dilute acid pretreatment process was optimized using a statistical method, and the relationships between each factor were investigated. Saccharification of pretreated rice straw was then performed, followed by fermentation of glucose, the hydrolysate of the saccharification process. The optimal dilute acid pretreatment process was as follows: temperature 110 °C, reaction time 14.02 min, and acid concentration 1.2%. Following dilute acid pretreatment, the solid weight was decreased by about 20% and 73.14% of the theoretical maximum content of xylose was solubilized. Glucose was recovered at a rate of about 90% at 24 h after rice straw was treated with dilute acid. Qualitative analysis such as SEM, XRD, and FT-IR were conducted after the pretreatment process, and the results supported the pretreatment process.     

微波烘焙预处理降解玉米秸秆

用微波可高效对生物质烘焙预处理,考察了不同微波烘焙过程对玉米秸秆主要组分的降解作用及酸、碱、甘油催化剂对纤维素转化效率的影响,并对预处理的玉米秸秆进行酶解实验。结果表明,单纯的微波预处理对玉米秸秆中主要组分纤维素、半纤维素和木质素均有强烈的转化作用。无催化剂微波烘焙后,样品中纤维素含量降低了30%。在微波烘焙中添加酸、碱、甘油催化剂,可选择性降解玉米秸秆中的半纤维素或木质素,有效提高预处理后玉米秸秆中的纤维素含量,添加NaOH后纤维素含量增加最明显,由33%增至42%,纤维素最高转化率达65%。     

酸碱预处理对芦蒿秸秆厌氧发酵的影响

通过对芦蒿秸秆进行酸、碱预处理和厌氧发酵制沼气实验,比较不同的预处理方法对芦蒿秸秆产气性能的影响。结果表明,与对照组相比,碱处理能较好地改善秸秆的产气性能,其中2%NaOH处理效果最好,发酵初期VFA含量高达4882.34 mg·L^-1,比对照组提高了705.21%,单位TS固体产气量为288.42 ml·g^-1,较对照组提高了17.08%,甲烷含量最高可达61.14%。     

Preparing bioethanol from oat hulls pretreated with a dilute nitric acid: Scaling of the production process on a pilot plant

The full cycle of bioethanol production from pretreated oat hulls is scaled for a pilot plant. The one-stage pretreatment of oat hulls with a dilute nitric acid at atmospheric pressure is scaled for a 250-L reactor. The total amount of hydrolysable polysaccharides in the resulting substrate is 87.2%. Using the commercially available enzyme preparations CelloLux-A and BrewZyme BGX and the industrial strain BKPM Y-1693 of Saccharomyces cerevisiae yeast, the process of enzymatic hydrolysis and alcoholic fermentation is successfully scaled for a 63-L reactor. The scaling factor is 1: 400. Bioethanol is obtained with a high yield of 17.9 daL/t. After rectification, the test sample of bioethanol meets the standards for high-purity alcohol from food raw materials according to the mass concentration of aldehydes, esters, and by the content of methanol.     

过氧甲酸预处理对甘蔗渣酶解和发酵的影响

以甘蔗渣(SCB)为原料, 经过氧甲酸(PAP)预处理后加入酶进行水解, 并以水解液发酵产乙醇, 考察预处理时过氧化氢(HPP)浓度变化对甘蔗渣酶解和乙醇得率的影响。实验结果表明: 在甘蔗渣PAP预处理过程中, HPP与甲酸(FAP)体积比为1∶1时, 预处理甘蔗渣(PAP-SCB-1)的木质素脱除率达84.30%;在纤维素酶用量为10 FPIU/g(以预处理后的甘蔗渣质量计)时, PAP-SCB-1水解72 h葡萄糖得率为98.71%, 较单独过氧化氢预处理甘蔗渣(HPP-SCB, 葡萄糖得率9.11%)和单独甲酸预处理甘蔗渣(FAP-SCB, 葡萄糖得率7.06%), 分别提高了9.84和12.98倍; PAP-SCB-1水解液经24 h发酵后, 乙醇得率为84.06%, 比HPP-SCB(76.20%)和FAP-SCB(75.15%)均有增加。对预处理前后物料的化学成分变化、比表面积和结晶度进行测定, 结果显示: 经PAP预处理后可以显著脱除甘蔗渣中的木质素, 木质素的量由未经预处理的21.27%降低到10%以下; 比表面积和结晶度都有提高, PAP-SCB-1的比表面积和结晶度分别为13.01 m²/g和54.18%, 是HPP-SCB的10.66和1.11倍, FAP-SCB的11.39和1.15倍。     

Enhanced enzymatic hydrolysis of rice straw pretreated by alkali assisted with photocatalysis technology

BACKGROUND: The fermentable sugars in lignocellulose are derived from cellulose and hemicellulose, which are not readily accessible to enzymatic hydrolysis because of their biological resistance, so that pretreatment of lignocellulose is needed for this process. In this work, a novel lignocellulose pretreatment method using alkali solution assisted by photocatalysis was investigated. RESULTS: The reaction conditions of nano‐TiO₂ dosage and photocatalysis time were optimized at 2 g L^?1 and 1 h, respectively. After pretreatment under these conditions, cellulose in rice straw was increased from 37.5% to 71.5%, and lignin decreased from 18.5% to 9.0%. The results of X‐ray diffraction (XRD), Fourier transform infrared (FT‐IR) and scanning electron microscopy (SEM) analysis showed that the physical properties and microstructure of the straw were changed by this pretreatment, which favored the following enzymatic hydrolysis. The enzymatic hydrolysis rate of the straw pretreated using this technology was verified to be 73.96%, which was 2.56 times higher than that obtained with the alkali procedure. CONCLUSION: The proposed photocatalysis pretreatment technology was more efficient at degrading the lignin and hemicellulose in rice straw than alkali pretreatment, making it more readily available for the following enzymatic hydrolysis process. Copyright © 2009 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     

酸碱结合预处理对水稻秸秆纤维素乙醇转化率的影响

以水稻秸秆为原料．在常温常压条件下分别用乙酸、过氧化氢、乙酸-过氧化氢（PPA）、氢氧化钠-PAA进行预处理,然后加入纤维素酶和酵母进行异步发酵产乙醇。结果表明,酸碱结合（氢氧化钠～PPA）处理后的固体得率显著低于乙酸或过氧化氢的单独处理,固体得率和纤维素水解后产生的葡萄糖浓度呈负相关;氢氧化钠-PAA处理能有效去除水稻秸秆中的木质素．大幅提高纤维素水解率和乙醇转化率;用10％氢氧化钠-PAA室温浸泡处理水稻秸秆48h与用5％氢氧化钠-PAA90℃处理水稻秸秆1．5h具有同样的效果。     

芒草酸/碱预处理副产物的生成及对乙醇发酵的影响

研究了不同浓度酸/碱预处理下芒草预处理上清液中副产物的生成和预处理上清液发酵产乙醇的规律,并对预处理副产物与乙醇发酵的关系进行了相关性分析。结果表明:酸/碱预处理上清液中预处理副产物浓度差异较为明显,酸处理产生的糠醛、5-羟甲基糠醛浓度明显高于碱处理,而碱处理上清液中丁香酸、香草醛、对香豆酸、阿魏酸浓度明显大于酸处理;预处理上清液补糖发酵中,1%H₂SO₄预处理上清液糖醇转化效率高于10 g/L NaOH预处理,半纤维素含量高和木质素含量低的材料具有较高的糖醇转化效率;糖醇转化效率与相应预处理上清液中副产物浓度相关性分析显示,糖醇转化效率与5-羟甲基糠醛呈极显著正相关,相关系数达0.795,与香草醛和丁香酸分别表现为极显著和显著负相关,相关系数分别为-0.811和-0.671。     

一株利用稻草秸秆发酵产油脂菌株的筛选及其发酵条件的初步研究

从土壤中筛选到一株能在纤维素刚果红培养基上生长的真菌,经形态学和ITS全序列分析鉴定该菌株为长孢被孢霉PFY。菌株在发酵过程中不需额外添加纤维素酶就可直接利用预处理后的稻草秸秆进行发酵生产油脂。利用气质联用技术分析了所产油脂成分,该油脂中含有较多的不饱和组分,其中油酸和亚油酸百分含量为31.70%和27.30%。对其利用预处理后的秸秆进行发酵因素的考察,适宜发酵条件为底物浓度20g/L,初始pH6,温度28℃,接种量2%,添加0.2%KH2PO4和0.05%ZnSO4。在适宜条件下发酵后油脂得率为8.15%。     

Effect of Modified Enzymatic Catalysis on the Extraction of Diosgenin from Dioscorea zingiberensis C. H. Wright

Multi‐enzymatic catalysis combined with acid hydrolysis is studied in order to enhance the efficiency of the enzymatic catalysis and reduce the mass transfer resistance from starch and cellulose in the extraction of diosgenin from Dioscorea zingiberensis C. H. Wright. The cellulase is modified by polyethylene to increase its optimal reaction temperature and pH value. The modified cellulase shows better thermostability and resistance to alkali. The modified cellulase, α‐amylase and β‐glycosidase are used to construct the multi‐enzyme and multi‐enzyme catalysis is used as a pretreatment process. Compared to primary industrial techniques including acid hydrolysis, spontaneous fermentation and enzymatic catalysis, conventional techniques are optimized by using multi‐enzymatic catalysis together with acid hydrolysis because of the higher reaction efficiency and lower levels of manipulation required. The purity of the product is more than 96 % with this technique, and the melting point is 205–207 °C. The diosgenin yield rate and the extraction rate reached are 2.43 % and 98 %, respectively. IR and ¹H NMR spectroscopy were used to confirm the structure of the product.     

氧气辅助湿热预处理对玉米秸秆酒精发酵的影响

为了解氧气（O₂）在玉米秸秆湿热预处理中的作用,优化玉米秸秆酒精生产工艺,本文采用三种不同湿热预处理条件处理玉米秸秆,即条件1（195℃,15min）、条件2（195℃,15min,12bar O₂）和条件3（195℃,15min,12bar O₂,2g/L Na₂CO₃）,并利用酿酒酵母对预处理后的玉米秸秆同步糖化发酵酒精工艺（SSF）进行了研究。实验结果表明：经过预处理,玉米秸秆分为固体滤饼与水解液两部分,其中绝大部分纤维素以固体形式保留在滤饼中,而半纤维素和木质素由于不稳定则发生了部分水解或降解。三种预处理条件下纤维素总体收率分别为91.2%、94.6%和95.9%,半纤维素总体收率分别为74.5%、50.3%和68.2%,固体滤饼中木质素质量分数分别为25.2%、17.5%和13.7%,纤维素酶解葡萄糖率分别为64.8%、65.8%和67.6%。表明氧气对纤维素收率影响不大,能够促进半纤维素的溶出。氧气主要与木质素发生反应,尤其与碱性物质碳酸钠（Na₂CO₃）结合,能够促进木质素降解,从而获得了较高的纤维素收率和纤维素酶解葡萄糖率。因此在底物质量分数8%,经过酿酒酵母142h发酵,经条件3处理的玉米秸秆获得的酒精浓度最高,最终酒精浓度达到25.0g/L,并且整个发酵过程没有明显的抑制作用产生。