Bioconversion of corn stover hydrolysate to ethanol by a recombinant yeast strain

Three corn stover hydrolysates, enzymatic hydrolysates prepared from acid and alkaline pretreatments separately and hemicellulosic hydrolysate prepared from acid pretreatment, were evaluated in composition and fermentability. For enzymatic hydrolysate from alkaline pretreatment, ethanol yield on fermentable sugars and fermentation efficiency reached highest among the three hydrolysates; meanwhile, ethanol yield on dry corn stover reached 0.175 g/g, higher than the sum of those of two hydrolysates from acid pretreatment. Fermentation process of the enzymatic hydrolysate from alkaline pretreatment was further investigated using free and immobilized cells of recombinant Saccharomyces cerevisiae ZU-10. Concentrated hydrolysate containing 66.9 g/L glucose and 32.1 g/L xylose was utilized. In the fermentation with free cells, 41.2 g/L ethanol was obtained within 72 h with an ethanol yield on fermentable sugars of 0.416 g/g. Immobilized cells greatly enhanced the ethanol productivity, while the ethanol yield on fermentable sugars of 0.411 g/g could still be reached. Repeated batch fermentation with immobilized cells was further attempted up to six batches. The ethanol yield on fermentable sugars maintained above 0.403 g/g with all glucose and more than 92.83% xylose utilized in each batch. These results demonstrate the feasibility and efficiency of ethanol production from corn stover hydrolysates.     

生物转化法生产2-苯乙醇动力学研究

考察了酿酒酵母(Saccharomyces cerevisiae)在5L发酵罐中转化生成2-苯乙醇过程中的菌体生长、产物生成和基质消耗的变化规律,并基于得到的实验数据,建立了转化过程中菌体生长的Logistic模型、2-苯乙醇生成的Luedeking-Piret模型和蔗糖消耗的Luedeking-Piret相似模型。将3个动力学模型的理论值和实验值进行了比较,表明模型具有较高的拟合精度,能准确反映2-苯乙醇生物转化过程及其动力学特征,可用于酿酒酵母转化生产2-苯乙醇过程的预测。     

Detoxification and concentration of corn stover hydrolysate and its fermentation for ethanol production

Environmental and energy concerns have increased interest in renewable energy sources, particularly biofuels. Thus the fermentation of glucose from sulfuric acid-hydrolyzed corn stover for the production of bioethanol has been explored using a combined acid retardation and continuous-effect membrane distillation treatment process. This process resulted in the separation of the sugars and acids from the acid-catalyzed hydrolysate, the removal of most of the fermentation inhibitors from the hydrolysate and the concentration of the detoxified hydrolysate. The recovery rate of glucose from the sugar-acid mixture using acid retardation was greater than 99.12% and the sulfuric acid was completely recovered from the hydrolysate. When the treated com stover hydrolysate, containing 100 g/L glucose, was used as a carbon source, 43.06 g/L of ethanol was produced with a productivity of 1.79 g/(L· h) and a yield of 86.31 %, In the control experiment, where glucose was used as the carbon source these values were 1.97 g/(L·h) and 93.10% respectively. Thus the integration of acid retardation and a continuous-effect membrane distillation process are effective for the production of fuel ethanol from com stover.     

分级式冲击磨制备玉米秸秆粉体工艺参数

分级式冲击磨是应用十分广泛的超细粉碎设备,但目前对分级式冲击磨的一些工艺参数的研究还不够充分。为了得到科学、合理的分级式冲击磨的工艺参数,本实验选用切断的玉米秸秆作为实验原料,用锤片式破碎机对其进行破碎并过筛（筛网孔径4mm）,通过分级式冲击磨对粗破过筛后的玉米秸秆进行粉碎。实验考察了二次风风门开闭情况、锤头数量、锤头周向速度对玉米秸秆粉体产量及设备单位能耗的影响。实验结果表明,二次风风门全开时,粉体产量比二次风风门关闭时提高43.6%;锤头数量为8个时,粉体产量比锤头数量为4个和16个时高,单位能耗比锤头数量为4个和16个时低,但差距并不明显;锤头周向速度为130m/s时,粉体的产量比锤头周向速度为120m/s、110m/s、100m/s时高。     

Simultaneous saccharification and fermentation of alkaline-pretreated corn stover to ethanol using a recombinant yeast strain

Bio-ethanol converted from cheap and abundant lignocellulosic materials is a potential renewable resource to replace depleting fossil fuels. Simultaneous saccharification and fermentation (SSF) of alkaline-pretreated corn stover for the production of ethanol was investigated using a recombinant yeast strain Saccharomyces cerevisiae ZU-10. Low cellobiase activity in Trichoderma reesei cellulase resulted in cellobiose accumulation. Supplementing the simultaneous saccharification and fermentation system with cellobiase greatly reduced feedback inhibition caused by cellobiose to the cellulase reaction, thereby increased the ethanol yield. 12 h of enzymatic prehydrolysis at 50 °C prior to simultaneous saccharification and fermentation was found to have a negative effect on the overall ethanol yield. Glucose and xylose produced from alkaline-pretreated corn stover could be co-fermented to ethanol effectively by S. cerevisiae ZU-10. An ethanol concentration of 27.8 g/L and the corresponding ethanol yield on carbohydrate in substrate of 0.350 g/g were achieved within 72 h at 33 °C with 80 g/L of substrate and enzyme loadings of 20 filter paper activity units (FPU)/g substrate and 10 cellobiase units (CBU)/g substrate. The results are meaningful in co-conversion of cellulose and hemicellulose fraction of lignocellulosic materials to fuel ethanol.     

微生物转化生产2-苯乙醇的原位产物转移技术研究进展

阐述了微生物转化法生产天然2-苯乙醇的代谢途径以及2-苯乙醇对微生物的毒性即产物抑制作用,而原位产物转移技术（ISPR技术）可有效降低产物抑制作用,提高2-苯乙醇产量。着重介绍了微生物转化生产2-苯乙醇的ISPR技术的研究现状,比较总结了萃取、吸附与基于膜分离的渗透蒸发和渗透萃取技术的优缺点,提出今后的研究重点应是将开发ISPR技术与培育高产量菌株和高效发酵工艺相结合,利用相对简单的设备及后处理技术即可显著提高2-苯乙醇的产率,早日实现微生物转化生产2-苯乙醇的工业化。     

在紫外光下以玉米秸秆为牺牲剂提升光催化分解水制氢

将玉米秸秆加入Pt/TiO₂的悬浊液中,在紫外光照射下实现了光催化分解水制氢速率的提升。通过SEM、XRD、FT-IR和TGA对玉米秸秆在光催化反应后的结构特征的变化进行了表征和分析讨论。通过单因素实验和正交实验研究了辐照时间、玉米秸秆颗粒浓度、秸秆颗粒粒径和催化剂浓度对氢气产率及产氢量的影响。实验结果表明：催化剂浓度和秸秆颗粒浓度对产氢的影响较大。产氢量随着催化剂浓度的增加先增后减,在催化剂浓度为4\times10^-3～6\times10^-3 g/ml时产氢量最高。当秸秆颗粒浓度大于0.5\times10^-3 g/ml时,产氢量随着秸秆颗粒浓度的增加出现明显的下降,而且在不同的秸秆颗粒浓度下氢气产率随着反应时间的增加呈现出不同的变化规律,而过小的秸秆颗粒粒径会产生负面的影响。     

玉米秸秆酶水解条件的优化研究

采用响应曲面法对玉米秸秆酶水解反应进行了评价,从而确定玉米秸秆酶水解反应的优化条件为底物中酶浓度57.5 FPU/g,底物质量浓度64.7 g/L,温度48℃,pH值4.8,反应时间49 h。在此条件下,每100 g底物还原糖产量为46.34 g,与模型预测值46.43 g底物非常接近。与单因子实验相比,酶浓度降低了2.5 FPU/g,底物质量浓度提高了14.7 g/L,反应时间缩短了23 h,还原糖产量提高10.41%。响应曲面法优化玉米秸秆酶水解是合理有效的,得到的优化条件有利于玉米秸秆的转化生产还原糖。     

秸秆固化成型燃料引火助燃剂的点火和烟气排放特性(英文)

Ignition-assisting agents for densified corn stover briquette fuel(DCBF) were developed,and their ignition and emission characteristics were investigated using type LLA-6 household cooking stove.Three waste liquid fuels,waste engine oil(E) ,diesel oil(D) ,and industrial alcohol(A) ,were used as raw materials to make 25 ignitionassisting agents by mixing at different ratios.Their ignition performance was evaluated in terms of ignition time and cost.It was found that ignition-assisting agents ED15(a mix of E and D at volume ratio of 1︰5) and DA51(a mix of D and A at volume ratio of 5︰1) presented better ignition results with shorter ignition time(40-53 s) and lower cost(6.1 and 5.3 cents) at the dosages of 9 ml and 8 ml,respectively.The emission of O2,CO,CO2,NOx,and SO2,the temperature in fume gas,and combustion efficiency were investigated for ED15 and DA51.The results show that the emission of ED15 with the dosage of 9 ml is lower than that of DA51 with the dosage of 8 ml in the ignition process.ED15 at the dosage of 9 ml achieves satisfactory combustion efficiency and emits less pollutant,so it is recommended for practical application.The study will provide a cost-effective and environmentally friendly approach to fast ignite DCBF and break the barrier to the practical application of DCBF.     

Porous carbonaceous materials from hydrothermal carbonization and KOH activation of corn stover for highly efficient CO2 capture

Sustainable biomass-derived carbon materials were produced by hydrothermal carbonization of corn stover that was followed by chemical activation with KOH. The prepared carbon materials were used for CO₂ adsorption and had a CO₂ uptake of 7.14?mmol/g at a pressure of 1?bar and at 0°C that was much higher than CO₂ uptake by activated carbon that was prepared from direct activation of corn stover (2.78?mmol/g). The porous corn stover-derived carbonaceous material had high surface area (2442?m²/g) and large pore volume (1.55?cm³/g). Product yields obtained by the activation of hydrothermally carbonized corn stover were significantly higher than those obtained by the direct activation of corn stover (36–75?vs. 8%). The prepared corn stover-derived porous carbon had a high CO₂/N₂ selectivity of 15.5 and exhibited constant CO₂ uptake for five successive reuse cycles. The hydrothermal carbonization step plays an important role for producing porous carbons from biomass that have high and specific adsorption properties.     

Microalgal biomass as a fermentation feedstock for bioethanol production

BACKGROUND: The increasing cost of fossil fuels as well as the escalating social and industrial awareness of the environmental impacts associated with the use of fossil fuels has created the need for more sustainable fuel options. Bioethanol, produced from renewable biomass such as sugar and starch materials, is believed to be one of these options, and it is currently being harnessed extensively. However, the utilization of sugar and starch materials as feedstocks for bioethanol production creates a major competition with the food market in terms of land for cultivation, and this makes bioethanol from these sources economically less attractive. RESULT: This study explores the suitability of microalgae (Chlorococum sp.) as a substrate for bioethanol production via yeast (Saccharomyces bayanus) under different fermentation conditions. Results show a maximum ethanol concentration of 3.83 g L^?1 obtained from 10 g L^?1 of lipid‐extracted microalgae debris. CONCLUSION: This productivity level (～38% w/w), which is in keeping with that of current production systems endorses microalgae as a promising substrate for bioethanol production. Copyright © 2009 Society of Chemical Industry     

Kinetic studies of xylan hydrolysis of corn stover in a dilute acid cycle spray flow-through reactor

Xylan of corn stover was pretreated with 1%, 2% and 3% (w/w) sulfuric acid at relatively low temperatures (90°C, 95°C and 100°C) in a dilute acid cycle spray flow-through reactor (DCF). The hydrolysis of xylan to its monomeric xylose was modeled by a series of first-order reactions. Both biphasic and Saeman hydrolysis models were applied to fit the experimental data. The results confirmed that the kinetic data of xylan hydrolysis fitted a first-order irreversible reaction model and the experimental data. The reaction rates of xylose monomer formation and degradation were sensitive to catalyst concentration and temperature. Higher catalyst concentration and lower reaction temperature result in high xylose yield. The activation energy for xylose formation and degradation were determined to be 112.9 and 101.0 kJ·mol^-1, respectively. Over 90% theoretical xylose obtained from corn stover can be used to produce ethanol, xylitol and fumaric acid by fermentation.     

玉米秸秆中不同木质素脱除方法对纤维素酶吸附及酶解效果的比较

利用不同预处理方法获得的玉米秸秆底物研究木质素脱除对纤维素酶吸附量及酶解效率的影响。相比于其他处理方法,2%(质量分数)NaOH处理的底物具有最高的木质素脱除率(85%),最高的底物可及性[4.7 mg·(g 葡聚糖) ^-1]及酶解效率(18.9%)。通过对不同处理获得的底物进行Langmuir吸附等温曲线模拟,获得了最大吸附量(W_max)与吸附平衡常数(K),且木质纤维素酶水解效率与纤维素酶吸附量具有很好的线性关系(R²>0.8),表明脱除木质素能很好地提高底物可及性与酶解效率。然而,提高NaOH浓度(3%,4%)进一步脱除木质素时,底物可及性与碳水化合物转化为单糖的效率反而明显下降。因此,适当脱除木质素而提高底物对纤维素酶的可及性将有助于获得更有效的酶水解效果。     

肉桂内生菌Sphingomonas sp.Z45生物转化肉桂醇生成天然2-苯乙醇

从新鲜肉桂枝中筛选出一株高效转化肉桂醇合成天然2-苯乙醇的内生菌,经鉴定为鞘氨醇单胞菌,并命名为Sphingomonas sp. Z45。采用GC-MS法对代谢中间体进行跟踪监测,推测了其可能的代谢途径为:肉桂醇先被氧化、脱羧生成苯乙醛,苯乙醛加氢还原得到产物2-苯乙醇。考察了单因素实验对该生物转化体系的影响,得到反应优化工艺条件为:初始pH=7,接种量5%,三角瓶(150 mL)中装液量为20 mL,菌体培养24 h后,加入底物肉桂醇质量浓度2.5 g/L,在30℃、转速为200 r/min的摇床反应12 h。在该优化条件下,肉桂醇转化率为59.16%,2-苯乙醇质量浓度达到1.48 g/L。     

重组酵母发酵半纤维素水解液生产酒精的研究

玉米秸秆中的半纤维素主要由五碳糖组成,普通的酿酒酵母不能发酵五碳糖。今利用基因重组酵母Sacchromyces cerevisiae ZU-10发酵玉米秸秆半纤维素水解液生产酒精,针对半纤维素水解液中的主要发酵抑制物,研究了硫酸根离子、乙酸、糠醛对重组酵母生长的影响,发现S.cerevisiae ZU-10细胞对SO42·,乙酸和糠醛的耐受浓度分别为5g·L·1、0.25g·L·1和0.08g·L·1。对玉米秸秆半纤维素的水解工艺进行了比较研究,结果表明,玉米秸秆采用1%H2SO4(固液比1:10),在95℃水解12h,其中的半纤维素水解率达到93%,发酵抑制物相对较少。半纤维素水解液经石灰中和、真空浓缩及离子交换处理后,可用于酒精发酵。半纤维素水解液的糖浓度与浓缩倍数及发酵抑制物浓度成正相关,对于重组酵母S.cerevisiae ZU-10,半纤维素水解液的适宜糖浓度为80g·L·1。在此浓度下,接种量1.2g·L·1(细胞干重计)、30℃、厌氧发酵96h,酒精浓度为31.05g·L·1,水解液中的木糖利用率达到95.85%。该研究结果对于促进半纤维素资源的转化利用,加速秸秆酒精的产业化进程具有重要意义。     

Selective hydrogenation of ethyl phenylacetate to 2-phenylethanol: a convenient catalyst preparation method

A ruthenium-tin-alumina catalyst, prepared by a combination of kneading and impregnation methods, which we have named the combination method, was able to selectively hydrogenate ethyl phenylacetate to 2-phenylethanol; tin oxide was used as a chloride-free tin source. For this combination catalyst, the optimum atomic ratio for Ru: Sn was found to be 1 4. X-ray diffraction measurements showed the presence of tin particles. It appeared that the number of the tin particles had a large effect on the hydrogenation of C=O groups. However, the catalyst prepared with ruthenium oxide had a low activity, possibly owing to the ruthenium metal or ruthenium-tin alloy, which was formed and which obstructed the reaction.     

Cerbera odollam (sea mango) oil as a promising non-edible feedstock for biodiesel production

This paper explores the feasibility of converting Cerbera odollam (sea mango) oil into biodiesel. The first part of this study focused on the extraction of oil from the seeds of C. odollam fruits, whereas the second part focused on the transesterification of the extracted oil to fatty acid methyl esters (FAME). The transesterification reactions were carried out using three different catalysts; sodium hydroxide (NaOH) as a homogenous catalyst, sulfated zirconia alumina and montmorillonite KSF as heterogeneous catalysts. The seeds were found to contain high percentage of oil up to 54% while the yield of FAME can reach up to 83.8% using sulfated zirconia catalyst.     

常见离子对玉米秸秆为牺牲剂的光催化制氢影响

以玉米秸秆为牺牲剂、Pt/TiO₂为催化剂,研究玉米秸秆不同部位、不同组分以及液相环境的pH、常见阴阳离子的加入对光催化制氢的影响。利用XRD、TGA和UV-vis DRS表征玉米秸秆的组分和光吸收特性。结果表明,在pH=5~7时制氢量适中、pH<5和pH=8~10时制氢受到抑制、pH>10时制氢得到提升;强酸阴离子、强碱金属离子对该体系制氢无影响;\mathrm{C}{\mathrm{O}}_{\mathrm{3}}^{\mathrm{2}-}和\mathrm{H}\mathrm{P}{\mathrm{O}}_{\mathrm{4}}^{-}对制氢有不同程度的促进作用;Fe³⁺、Cu²⁺和Zn²⁺因其氧化性强弱顺序和弱电离性对制氢有不同程度的抑制作用。综合上述实验结果分析了不同离子对制氢影响规律和作用机理。     

改性玉米秸秆对Cu2+吸附性能研究

研究了NaOH、HNO3改性玉米秸秆对水中Cu^2+的吸附性能及吸附特性。研究表明,改性后的秸秆表面光滑,结晶指数高,对Cu^2+的吸附容量增大。相比未改性玉米秸秆和酸改性玉米秸秆,碱改性玉米秸秆对Cu^2+的吸附效果最好。碱改性玉米秸秆对Cu^2+的吸附能较好地符合Freundlich方程和伪二级动力学模型。初步推断吸附机理是秸秆表面官能团与Cu^2+络合形成复合体的化学吸附过程。     

Continuous process for yeast biomass production from sugar beet stillage by a novel strain of Candida rugosa and protein profile of the yeast

Thermotolerant yeast Candida rugosa isolated from East Africa was used for the continuous production of yeast protein from sugar beet stillages at 40°C. At a dilution rate of 0·15 h⁻¹, biomass productivity was at a maximum (0·85 dm⁻³ h⁻¹) and the Chemical Oxygen Demand reduction rate of the stillage was 30·4%. This yeast contained 45·1% crude protein, 36·5% actual protein and 5·6% RNA. The yeast protein had adequate essential amino acids, except for sulphur-containing types.